First, the standard repetitive background info: This is in regard to an engine rebuld on my '89 IROC (L98 engine) that I'm trying to finish...

If you've read my first post about this... this is a different post, so keep reading.

Okay, basically I've been running into a problem with overheating (the kind that would peg the temp gague). I've tried different things, but here's the latest: I've since completely removed the thermostat and ran the engine without it (when I had it out, I put it into boiling water, and it only barely opened--so mabye it was bad). After I did that, it actually took a while to warm up. After mabye ten minutes of running time, though, it was approaching 220 degrees, and it slowly kept on getting higher after that. As it started to approach the redline, I figured that it wasn't going to stop heating up, so I went to the fan relay for the secondary fan and I shorted the relay to force the second fan to stay on. After doing this, for the first time, I was actually able to keep the temp stablized: the temp gague made its way down to 220, and stayed right about there for the next fifteen minutes until I shut it off (this was the first run that was longer than 20 minutes).

So, I know I've heard that rebuilt engines are supposed to run a little hotter than higher-mileage engines. Is 220 degrees too hot even for a rebuilt engine? Remember that this is 220 degrees without the thermostat, and with the both fans forced to be on.

I guess that I'm just worried that I'm artifically lowering the temperature, and by doing that I'm just "masking" the real problem which I've yet to find. Should I be satisfied with this for now, or do you think that I still have other problem(s) that I need to investigate?

Thanks

 

I think that if you do not have a thermostat in it that you are running to hot. My car has never had a problem with overheating. However, i know that my friends car has a radiator without the thermostat on his truck and it runs at most 120 on a hot day. If you have to artificially cool it down then you probaly have another problem. Does it need to be flushed? Maybe the cooling sytem is plugged somewhere or the water pump is out. With cooling systems it can not be to many reasons for overheating. You should be able to diagnose the problem yourself.

 

220* it a little warm with no stat. When does your fan come on? when you want it , or at a certain temp?

Is this happening while driving, or sitting?

You have an air dam right?

 

New engine ? I'd say BIG vaccum leak somewhere.

 

As far as the cooling system goes, I'm pretty sure that it is in decent shape. The water pump is new, and is a high-output pump, so I can visibly see the flow in the radiator upon startup (so turbulent that it almost pours out of the filling hole). What I can say, however, is that the cooling system was rusted over before this rebuild (and might well have been a big reason for the rebuild). When I got it from the previous owner, there were rust stains all over the front of the engine--I guess from a previous instance of overheating. Basically, there was rust all throughout the coolant system (the radiator, pump, hoses, and block). The major part of the rust, however, has been cleaned out (the whole block was "acid bathed" or whatever they do when they do the rebuild). All of the hoses are new, and the coolant looks relatively clean. So unless the little bit of rust that is left in the block and radiator can really retard heat transfer (and there is still some rust left in there), I think the coolant system should be in good shape.

As far as fans go... all I can say is that the secondary fan is working as GM intended it to (comes on at ~238 degrees, which is too high IMHO, hence I manually intervened), and the primary fan seems to have been rigged by the previous owner. It seems like it's working backward--it's on when it should be off, and it's off when it should be on. But I can't confirm that--like on this last run, it stayed on the whole time. Generally, though, its always on. They're new fan motors, too.

Oh, and this is all happening with the car on stands on my driveway; I do have an air dam, but that wouldn't make a difference on my driveway.

And for the vacuum leak thing... I actually hadn't thought about that, but now that you bring it up, I would like to check that out. Hopefully I can get a gague for cheap. How much vacuum should I have and at what engine speed?

Thanks for the replies; keep 'em comming.

 

I think 220 under no load is too high...doesnt leave alot of room for work. I agree with the vacuum (sp) leak also..I wwould check the intake manifold for leaks....exactly what my wifes cutlass did when the gasket was shot..good luck.

 

Okay, well I've since bought a new vacuum gague and hooked it up. I'm reading about 16 millibars (I think that's the unit) of vacuum at idle (at a ~1200 RPM idle, actually). As far as I know, that's pretty reasonable, right?

So, vacuum leak aside ('cause I don't think I have one--correct me if I'm wrong), what else could be causing the overheating? I had a long post a while back that sort-of died, but one guy recommended that I adjust my valve lash. I know I probably need to do that anyway, but I still don't see how that could make things overheat.

And as for timing... if I set the base timing to spec, the car willl neither idle or start.

Any other ideas?

 

220 deg at idle is not unreasonable. Remember, there is no air flow across the radiator at all. Also removing your thermostat and leaving it out will actually make the engine run hotter. With the thermostat in place it keeps the coolant in the block under constant pressure, which keeps things cooler. And on the pressure thing, have you replaced your radiator cap? With a weak cap on the system it will run hotter also.
Your fans are another issue all together, they both should be operating when the coolant temp gets that high. You need to get them both operating properly and see what that does for the cooling.

 

Sancho, ignore the above post! Whew! Bad info.

220 at idle, with no T-stat, and both fans churning away, is too hot. Obviously there is air flowing over your radiator; both the fans are running! Further, just as you properly reasoned, removing the thermostat will make the car run COOLER, not hotter. Yes higher presure (forcing the coolant against the cylinders and radiator "harder"for greater heat transfer) increases cooling, but that presure is not intended to come frome the T-stat, it is intended to come from the expansion of the heated coolant, which is regulated by the radiator cap.

So, sancho, you are on the right track for the most part. My recomondations are:

Check Radiator cap for sure

Ignition timing?

Vacuum. I'm not sure what your engine combo is or what elevation you are at, but 16" at ~1200 RPM seems too low. I would investigate that too.

Do you still have the AC condenser in? Is there crap between that and the radiator?

Do you have a temp probe or thermocouple that you can check the coolant temp on the inlet side of the rad and then on the outlet side, looking for a substantial drop?

My 400 CID T/A idles at 1000 RPM at 170*, with a 160* T-stat. The elecric fan cycles on, and off about every 30 seconds. So again, no T-stat, two fans running, 220* is too hot. Something else is wrong.

 

My 327 has never seen 220.....sitting in traffic...mechanical fan...heat of the day kinda stuff...Up to a point no thermostat will run cooler, after higher temp is reached the coolant doesnt get the time in the radiator to cool off..it is cycling all the time ...I can see Morley's point on that issue..but still you do have an issue somewhere.......does the temp rise and fall alot or just rise and keep going up?

 

Morley -- I do really appreciate the reply and your trying to help; however, I would tend to agree with the others that 220 is too hot (that's with both fans being forced on, no thermostat, and being on for mabye ~20 min).

Riley -- Basically, the temp just keeps on going up. With the thermostat out, it [the gague] does take a while to actually start moving, but once it starts warming up, it steadily (and slowly) increases. My expreince has been that it will continue to go up into the red line, except that I've never let it get that far (actually, I did once, but that's when I learned my lesson). That's with the primary fan always going. I actually don't wait long enough to let the secondary come on--I'll end up forcing it to come on by jumpering the relay-socket before it decides to come on automatically, just to try to keep the engine safe.

Tom --

-- The radiator cap is new, so I'll just assume that it checks-out.

-- As far as vacuum, I have no concept of how much is considered "good". I do know that vacuum can vary with different cams, but I made sure to put basically a "stock" cam in (new, but with stock specs). Mabye it's apples-and-oranges, but I put the vacuum gague on my 2.8L Camaro (which doesn't have any problems aside from being a 2.8 V6), and I got a similar reading at idle (although the idle is ~800 RPM on that car). So, even if there is a leak, it can't be all that big.

-- The AC condenser is in, but we had the radiator out for the rebuild, so there's no way that there are any leaves left (unless on the front of the condensor). I did hit the condenser by accident when the radiator was out and screwed up the passenger's side pretty bad, but I managed to comb it out. Still looks bad, but it should flow air...

-- Ignition timing... I'm still gravitating to this being the culprit, but it also happens to be the thing that I have the least experience with. All I can say about the timing issue is that we've (my dad and I) played with it. We did the whole thing with disconnecting the timing wire, putting a timing light on it to set the base timing, turning it off, and then reconnecting the wire. The problem there is, if I set the timing to what it's supposed to be, the car won't idle or even start without really playing with the gas pedal. So, we've had to advance the timing a few degrees just to get it to start and idle--and when we do that, the idle speed is too high. So, like I said, I don't really have much experience in this area. Beyond doing with the book says to do (which doesn't work), I don't know what I'm really looking for (i.e. where the timing really should be). And I don't know if it has anything to do with it or not, but it has backfired through the intake a few times while it is running.

Anyone have any tips for me on the timing issue (because I wonder if that's where my problem really is)?

BT

 

Before we did this rebuild, the coolant system was basically filled with brown/orange water (meaning rust...). We did do a full coolant system flush before the rebuild. But, even when we got the block back after being machined (and magnafluxed, bathed, and everything else), I noticed that it still looked orange in the coolant channels in the block (meaning that there's basically rust still in the block that will never go away).

Is it possible that this rust could be inhibiting heat transfer in the block (and radiator too, I guess, since its insides are covered with orange as well)?

Just a thought... I *hope* that this is not the answer, because if it is, then I'm really screwed...

 

alright this is MY experience with no thermostat. it would get up to 220* at idle with the fan on under no load. try a 160* or 180* thermostat with a couple small holes drilled in it. post back here. i know a 160* stat with a couple holes in it cooled way better then no stat. and my car would go over 220* w/o a stat just idling with the fan on.

 

a lean condition will also cause high temps....Usually retarding the timing causes overheating not advance..correct me if I'm wrong.
Try setting the base timing at 6* advanced and go from there.

 

Sorry, missed the part about you forcing the second fan on. If 2 fans can't get it down under 200 deg then you have a problem. You mentioned having rust through out the system at one time, if you are using the same radiator you may need to clean it out, not just loose stuff. There may be calcium deposits through the radiator from hard water, the best way I have found to really clean out a radiator is to remove all the hoses and plug the holes, then put in 1 gallon of viniger and top off with water. Let this sit for about 24 hours and drain it, then flush it out real good with clean water. Hook everything back up and try again.

 

Yep a lean condition will cause a backfire at times, and overheating.

 

hey guy

First thing you need to do is put a 180 degree thermostat back in ( why, cause the thermostat helps to regulate flow of coolant thru the motor Ie: if the coolant flows to fast thru the motor it will not have time to have pulled any heat from the block in turn can make it heat up and boil over ) If it still heats with a new 180 stat you mentioned that it had a high flow pump on it. well that could be the root of the problem cause the water/antifreeze is flowing faster thru the block and it don't have time to get the heat from the block. also something to try is mix the antifreeze mix a little stronger so it is thicker that in turn will help slow down the flow of the circulation.

the reason i suggest a 180 is cause if it is a EFI car the ecm needs coolant temp to get it to go into closed loop and not stay in cold enrichment.

if your car is a TPI car it sounds like you might want to set your base idle setting then set your TPS.

 

Wrong, wrong, wrong. How in the world can an engine over heat if the coolant flows too fast to absotb heat? Then the coolant would be cool, right? So if there is cool, coolant flowing around the cylinders, how can they over heat? And if it is flowing so fast it doesn't absorb heat, how does it 'boil over'?

Please read this!
http://www.stewartcomponents.com/htm...t/techtip3.asp
http://www.stewartcomponents.com/htm...upport/faq.asp
http://www.stewartcomponents.com/htm...t.asp?m_id=695

 

ok please explain this to me. i had a basically stock LO3 when this was done. it was summer time and the temps were getting triple digits almost everyday. so i thought what the hell i will take my thermostat out. i took it out iw would take forever for that engine to get to 160*. my engine just idling would get up to over 220* without a thermostat. i put a 160* stat back in and going from 100-160* took a lot less time. also the car would stay around 160*. it would not get to 220*. if it is better to have a **** load of flow then why is some company making money off of these
more flow then stock is good, but you dont want 1 trillion gallons per minute going through the engine.

 

Check the radiator really, really carefully. You have to KNOW that it is good.

 

I don't know why your car behaved the way it did. I don't know anything about the status of your car, so I can't explain it's behavior. All I can suggest is that when a cooling system is on the brink of it's ability, it takes a very small change to make or break it's marginal ability to cool the engine. What ever that change is, that doesn't nesessarily mean that it applies to a properly functioning cooling system. I know on MY car (SB 400, stock aluminum rad, stock water pump, electric fan) no T-stat=a very cold engine. It bearly moves the temp gauge above 100*. It does perform as it should. The T-stat isn't designed to restrict flow. It does, but that is not what it's function is.

 

Well, here's where I'm at now...

Just a few hours ago, my dad and I adjusted the valve lash on the passenger's side of the car (what a *PITA* it is to get that passenger's side valve cover off). We actually ended up stopping at the passenger's side for today because, as my dad was adjusting them with the motor running, I leaned in and looked at the dash, only to notice the temp-gague entering the red-zone (at which point I immediately shut the engine off, forced both fans to stay on, and ran the engine for a couple of seconds a few times to re-circulate the coolant). I'm going to do the driver's side some other time this week (whenever I build up the patience to put the passenger's valve cover back *on*, as I'm sure it will be a PITA to put back on). I'm only adjusting the valve lash in response to another board-members suggestion (on another post) that I do so (got to try all of my options).

Also, instead of getting a cooler thermostat and/or drilling the thermostat, I think that I'm going to go for a high-flow thermostat. From the links that Brodyscamaro posted, I'm thinking that I should have had this all along since I'm using the HO water pump.

Hopefully, between the two, something will help the overheating problem (although I'd be lying if I said I wasn't skeptical).

So, thanks for all of the posts... I'm still open to suggestions. Other than that, I'll keep you posted.

 

lo

 

I agree with ya brody. sometimes better flow doesn't help out the problem.

But Tom what i was getting at is that the coolant, when it's flowing fast it can pull the heat out of the block. but if it's flowing fast thru the radiator then the heat exchange can't be done. ( i was gettting ahead of myself earlier in the post) thats why when he forced the fans to run it still ran at 220. cause the radiator couldn't do it's job correctly
here is an idea to try your motor with a high flow pump with no stat and see how it reacts.

Also if a t-stat is not designed to restrict flow how come some of the guys here that race circle track put a washer in place of a t-stat to keep the engine from overheating @ high RPM'S to help control flow so the radiator can do it's job correctly

 

also when i had no stat it was with a stock water pump, or was it with the stewart
oh well i forgot

 

sancho

I was sitting here thinking when it gets that hot does it boil over. have you ever thought that the sending unit in the head was bad.
just a thought might want to buy a cheap mechanical guagge to track and to see if the stock guage is reading correctly

 

SC2camaro -- Oh, it's getting that hot all right... Right after I turned the car off (immediately as I saw the temp gague was in the beginning of the red-zone), the radiator was very-obviously boiling over. It's got a new 13-lb cap on it.

I had both of the fans forced on, though, after I turned the car off, so it was only boiling for a minute or so, and then settled down pretty quickly. In comparison (if it's even a fair comparison), when the radiator has boiled over in my '88 Camaro [see the sig]--usually due to being in city traffic in the summer with the A/C on--I've seen it continually boiling over for ~5 minutes after I turn the car off (I didn't force the fan on in that car, though). And even when that car has boiled-over, I've never even seen the temp gague in the red-zone.

What that tells me is that the radiator and fans must be doing their jobs--else, it wouldn't quit boiling so quickly. Plus, between starting and stopping the engine for a couple of seconds a few times (to move coolant between the block and radiator), I was able to get the temp out of the red-zone and below 220 in mabye five minutes.

 

sancho,

I understand that your fan and radiator is doing there job while the water is standing still in the radiator. while it's standinf still it has time to take the heat away from the water. what the problem is that the radiator is not able to pull the heat out of the water why the water is circulating with it running. it's about like not having a radiator at all hot water in hot water out. eventully it will boil it over also i think the car could use a 16 lb cap.

a little tech for a for every lb of pressure put on water it can be be heated and additional 4 degrees

normal boiling temp @212
with a 16 lb cap @274
thats in the radiator

from what i have read it works that way correct me if i'm wrong guys

 

Actually, it supposed to have a 18 LB cap!

 

I gotta tell you, it sounds like something very basic is wrong.

Some possibilities:

Collapsing bottom hose (usually these have a coiled wire to reinforce them but you did mention a HO pump)?

Internally collapsed bottom or other hose (they can still look good from the outside)?

Clogged or internally corroded radiator (if only one or two rows are flowing you might be fooled into thinking it is still good -- is it possible for you to feel the rows and see if they are heating up uniformly?).

Blown head gasket.

Cracked block or head.

Possibly improper initial purging of trapped air in the system.

 

What your saying makes no sense. Let's pretend for a minute that what your saying is true. Let's assume that the car CAN maintain the proper temp at idle, because the coolant flow has been "restricted" enough to allow it to "transfer more heat". Now we rev up the motor. It should REALLY overheat now, huh? Now the coolant is flowing too fast again (water pump spinning faster), and the engine is also generating more heat because it is revving higher.

If faster coolant flow cause the coolant to transfer less heat, then by your theory, the cooling system would become dramaitcally less efficient as the engine RPM's increase. If that were true, all engines would over heat at high RPM's

Another way to look at it: You claim that water flowing too fast through the rad won't transfer heat. No matter HOW FAST you push water throught the rad, if air is passing through the rad, it wll be heated, right? The rad and it's fins are going to be just as hot as the coolant, regardless of the coolant's increase in speed. So air movign through the rad will increas in temp. This is heat transfer. The water could be moving 500 mph through the rad, and the fans will still be pumping hot air off the rad.

The cooling system transfers the most heat, the fastest, when there is the biggest difference in temps between two (ex rad and air), if you slow the coolant so much that it is in the rad for a longer peroid of time, it will cool and the rate of heat transfer will decrease, because the coolant will get close to the ambient temp. Do you get what I'm saying here? The faster you circulate heat, the better cooling will occur. If you have to "slow down" the coolant because the rad can't dissipate the heat fast enough, you need a better radiator.

 

okay. once again explain why my car acted the way it did. why are people making money off of these ?

 

The real problem with fast moving coolant is that it isn't in the radiator long enough for the heat to transfer to the metal in the radiator before it is run back through the block again.

 

So then then if the heat isn't transfering into the radiator because the cooland it moving too fast, the rad tubes and fins must be cold, huh?
If the radiator is hot, which it certainly would be, assuming it is in decent condition, it is, without a doubt, transferring heat.

Brody, I think thse restrictors are used to prevent the temp from running too LOW. If high coolant flow caused over heating in race cars, why don't they under drive the pulley more to gain afew more hp, while at the same time slow down the coolant speed to "prevent overheating"? Why would you waist hp to pump coolant "too fast" (causing overheating) just to plug up half the system to slow the coolant back down?

Again, pumping the coolant faster moves more heat away from the engine. You are re-using each limited quart of coolant more times per minute. That makes the cooling system more efficient.

 

hey sancho


on the HO water pump. you did get it for serpintine belt drive didn't you ? if you got a standard HO pump. the problem might be that it's pumping the water backwards thru the engine. the reason for asking is cause the newer pumps rotate in the reverse direction since the belt drives it on the back side of it's self making the pump pulley rotate in the other direction verses the crank pulley.


if you can look at A V-BELT drive pump and compare it to a serpitine belt drive pump. you will notice that the impellars are turn the other way so that it flows the coolant in the same direction.

it could be that your use a v-belt drive style pump on a serpintine belt drive aand tring to flow the water backwards and having the pump discharge the water away from the motor thru the bottom hose.

it might not be the cause but it's a thought just tring to help out guys

 

Hi Sancho,

Re-read your initial posts again and I am still thinking, "look at the radiator closely."

It could be that the highly turbulent flow you're seeing in the neck is from all or most of the flow being forced to go through a small number of rows (roughly think Bernoulli principle -- large volume forced through smaller passages).

It is a little unclear but it sound like the previous owner had a major overheating problem and was not able to solve it (or ran out of money?).

It also sounds like the PO did not use antifreeze or never changed it (all the rust)?

Is it also a correct assumption that the radiator is the one that came with the car (and maybe was responsible for the overheating?)?

Ok, naturally I could be just plain wrong but think about this...

Radiator is bad so the engine overheats. Engine overheating causes the seals on the water pump to finally let go. Owner sees leaking water pump and replaces it thinking it is the cause of the overheating when it is actually a symptom/effect. [BTW, yes, your description of the thermostat barely opening in boiling water means it is bad. Get a new one and compare its action in boiling water.] Engine overheating could have also damaged the block or heads and that might not have been detected during rebuilding unless specifically looked for (get a combustion gas detection kit for the coolant if this ends up being a last possibility).

Radiators generally have a useful service life. It is usually less than 12-13 years (1989 right?). One *could* last that long if the cooling system was properly maintained but we already know it wasn't (rust in the system). Because radiators are so expensive (or because you can't easily see inside them) people seem to have a natural tendency to want to try to replace cheaper items first. I know I did and still do.

Now, when I buy a used car I try to just figure that I will be putting a new radiator in. Saves on emotional drama.

Anyway, one last experience...

Bought a 66 Valiant from a lady in her 80s who drove it very little. I drove it a lot -- and faster, I'm sure. Radiator seemed okay until the car overheated on the Grapevine (I-5 in CA). My use of the car caused all of the rust in the block to be swept up and lodged in the cooling passages of the radiator. Voila, overheating. Same thing would have happened if I had put a new radiator in without flushing the block first.

Ok, so now that I have spent 1/2 hour thinking about your car again and typing this out, it will probably NOT be the radiator.

 

SC2camaro -- I didn't even think about that, but I'll check (hope I can still find the box). I do know that I looked really hard at the new and old pumps side-by-side before I put the new one on, and I couldn't find any significant differences. Hopefully, the instructions in the box will tell for sure.

Kevin Johnson -- I really don't know what the deal was with the previous owner. All that I can say for sure is that the engine compartment was pretty-well covered with orange spots caused by rust that originated at the radiator. I *think* that the previous owner had the radiator rebuilt, but I don't really know what that means (how could you "rebuild" a radiator--looks pretty much like one piece to me). I would agree with you on the lack-of-antifreeze part--he probably must have used pure water and left it in for a while. I don't know for sure, however, that the previous owner had any persistient heating problems; my dad drove the car straight home from about an hour away, and it was perfectly fine when he drove it up. I think that, if the car was so inherently prone to overheating, it would have overheated long before my dad made it home. And the reason for the engine rebuild had nothing to do with the cooling system--it had 160K miles on it and was leaking a lot of oil around the valve seals.

If I had the money, I would just go out and get a new radiator, but the car budget was tapped out a while back. I wonder this, though: I do have another camaro (the '88 Camaro SC in my signature) that is currently my daily-driver. Just temporarily (for troubleshooting purposes), could I take the radiator off of that car and put it into my IROC? I'd be curious to see if that fixes the problem...

 

yes you can swap the radiators...worth a shot. I must say this has been an interesting thread...:lala:

 

Before swapping radiators try this. Disconnect the hoses from the radiator and drain it, then plug the holes, next put about a gallon of viniger in the radiator and top off with water. Let this sit for 24 hours, then drain and flush the radiator with clean water. Hook everything back up and refill the radiator. See if this helps keep the temps down.

The radiator tubes may have become blocked by deposits from the water that was sitting in it all that time. The viniger will dissolve hard water deposits and the crud that may be blocking it up.

 

Damn... I just put both cars side by side, and wouldn't 'ya know, the radiator in my '88 Camaro (2.8L V6) is about 3-4 inches less wide than the one in the IROC. Actually, it's also backwards (the cap is on the driver's side and the upper hose is on the passenger's side--reversed in the IROC). Scratch that idea...