Black88Z

I have an 88z with the 350tpi thats been getting too hot lately. It had a 195* tstat in it that was new, now i put in a 180* and still have the same results. It does take slightly longer wth the 180* of course, but still gets up there.

It was fine when the outside temp was below 100*, but lately is been over 100* everyday for several weeks now. It would get to about 240* and i would pull over somewhere and let it cool off a bit. I dont know if it will get any higher than that or not because I wont let it, I always pull over and shut it off so nothing gets damaged.

The pervious owner hardwired the dual fans to the ign. switch, so they are constantly on if the key is in the ON position. I do know both fans are working.

There are no leaks or smoke, and my coolant level always stays at the same level in the rad. and the overflow.

Could an improper coolant/water mixture cause overheating like this? Im not sure of the mixture, but I do know I have way more water than coolant.

I've heard these cars came with an air dam, im not positive, but im pretty sure mine is there. There is a black plastic peice under the front lip that i believe is it. (this is the first part to scrape on a speedbump )

Ive checked everything i can think of, so i would really appreciate any help with this. With no cooler days in sight, id like to fix this problem immediatly- it sucks only being able to drive for about 20min in this heat before it gets too hot.

Thanks for the help

RBob

iTrader: (1)

Yes, the black piece that hits the speed bumps is the air dam. Check that the fans are blowing into the engine compartment, IOW, pulling air through the radiator.

Remove the upper radiator mounting piece, look down between the A/C condenser and radiator. It is common for that area to fill with debris. At about 60K miles my car was 1/3 of the way filled.

Check the base spark timing, should be at 6* BTDC. Do this on a warmed up engine with the EST/BYPASS connector open.

Other items are a clogged radiator, wrong rotation water pump, or bad injectors. Check/do the easy stuff first.

RBob.

chevelle600

iTrader: (9)

Do what RBob said. and yes, improper coolant mixture can cause higher (or lower) temps. water has a different boiling point than antifreeze. most cars reccomend 50% mixture.

you also have to remember stock GM gauges arent 100% accurate. my car runs at 220* when warmed up with a 180 stat and a 3 core radiator. thats with 1 fan on all the time. I dont have fan 2 relay plugged in. even with 100 degree days and high humidity I dont worry too much.

Black88Z

Those are very good suggestions RBob, i will do these shortly.

I dont know how old the water pump is, but i will check it for pressure by pinching the upper hose and letting go, to see how much pressure builds and how fast it goes thru.

My car sat for quite a while, so it could very possibly be clogged up between the condensor and radiator.

chevelle600: I do know the gauge should not be completely trusted, but since thats all I have to go by i would rather be safe than sorry. I will try to do a flush and put in 50-50.

Thanks for the advice, ill post back in a few with some results

Black88Z

Alright, well I did the tests/checks and heres what I found:

When pinching the upper rad. hose there was a good pressure build up, and when i let go it gushed right through as it should. I believe my water pump is fine.

I took the upper rad. support off and checked between the condensor and rad., there were leaves and other crud in there, but not as much as you said you had, RBob. There was still about an inch - 1 1/2in or so layer on the bottom, and there were some random leaves caught on the fins of the condensor and radiator that i pulled off as well. I did notice that there were groups of leaves on the "inside" side of the radiator, directly across from the fans. I think the suction of the fans sucked them up there and they got stuck there. I cleaned that area the best I could getting 99% of it all.

I did notice that somebody put about 1/4in of washers between where the fan mounted, but they only did so on the top. This didnt make any sense to me, and I know that the fan(s) should be as close to the rad as possible to pull more cool air thru the rad, rather than air from the engine bay around and thru the fans. I took them off and re-installed the fans and they fit much better. The left one still is slightly further out than the right, but you have to really look to notice, and even then its hardly noticeable.

I havent been able to drive the car today since, but I will tomorrow. Hopefully these things will fix my problem. Thanks for the advice guys, and ill keep you posted.

Scorpner

iTrader: (4)

Check that the coiled wire insert is in the lower hose. It keeps it from collapsing. (Should feel it if you squeeze it.)

You can clean the fins by spraying water from the back to front but be careful not to damage the fins when you do that. You might have to remove the fan to access it though. (Condenser too since that would block airflow too.)

You should be able to pick up an antifreeze tester to see what temps your mixture is currently good for. they have little ***** or a lever that floats to a certain level depending on what the mixture is. IIRC, they're $3-$5 or so.

And you might be able to rent one of those pressure testers for free at a local parts store if you want to check that again. You put down a deposit and get it back when you return it.

TreeFiddy

Sounds like your climatic temp situation atm is pretty similar to a typical summer here, and my factory single fan setup behaved much like yours, but would actually boil after 10 mins from cold, even with the fan just wired to ign run.

Replaced everything in the cooling system, from the rad cap to reco'ing the core. Still couldn't take the outside temps. After much stuffing around, what finally fixed it for me the two biggest fans I could find in the wreckers that still fit within the rad core.

Along with a full shroud that enclosed the rad and fans completely, to prevent any air loss between fans and rad, and engage 100% of the core area for cooling.

Stevolwevol

iTrader: (1)

We are in a heat wave here presently, and the temps are over 100 F. I still don't go over 195 ish.

TreeFiddy

Yeah, that's about where mine tops out now too. Once you've got pressurized coolant pumping freely around the system, seems to be just a matter of getting adequate airflow across the core by whatever means. More fans, more core, closer shrouding etc.

In addition, I found two other things that lowered running temps further, years after I had the overheating sorted. One was plumbing in the heater core full-time, which had been previously disconnected by a po (mines an 86, does not employ the vac valve of later models). The other was switching from ported to manifold advance (I'm carbed).

Black88Z

Well mine still gets too hot. I was doing good, it does take longer to get to 220 but it does get there. I should note that it seemed to stay around 195ish (with 180 t-stat) and then i started racing around and it went up to 220 fairly quickly lol. But i got to my house and shut it off, idk if it would go any higher or not. Im going to take it for another drive soon and try not to be so heavy footed to see how it does then (damn heavy foot! lol) Id be happy with 195 tho, and like i said usually it was around there until this brutal heat. If i drive it at night it stays around 195, too.

TreeFiddy

Sounds like your cooling system is normally just on the edge of being able to provide enough cooling power. The heatwave is stressing it beyond it's abilities. Still - if it's not actually boiling, you're still good.

If you've checked and replaced everything and it's all good, but you're still not happy with the cooling performance, time to find ways to increase airflow. Or just wait till the unusual heat passes. Back before I got mine nailed down, I had to pick my driving days too.

Remember gauge accuracy too - your 195-ish reading might not be my or Stevewol's 195-ish reading. My 195-ish reading might not actually be 195, though it agreed fairly close to my ir gun when I zapped the thermo housing iirc.

Black88Z

Nope, still does it. It got above 220*, still to about where it would usually get to.

I noticed that when i put it in neutral and coasted for about 10seconds or so i could actually see that the needle had gone lower, closer to 220.

Is it possible a detent cable for the tranny could cause this problem if its too tight? I love the shift points, but ive noticed that it doesnt always quite shift when it should, sometimes it'll stay at around 3k+ rpms for a while until im able to speed up more and it will finally shift. I adjusted the detent cable myself, and i do think it is a little too tight but im not sure. It shifts out of 1st at about 12 under normal driving, then into 3rd at about 30-35 i believe, then into 4th at about 45. Im not sure if that could cause it, but thought i should mention it. (maybe tranny is getting too hot, causing the rad. to get hotter than it should from the hotter tranny fluid, and making the engine hotter?)

Scorpner

iTrader: (4)

If your TV cable is not adjusted correctly it can damage the transmission, I've never heard of one being too tight though.

Stevolwevol

iTrader: (1)

Maybe your sending unit or gauge is not accurate.

Black88Z

Well what i mean by too "tight" is that it doesnt always shift when it should, rather than upshifting it stays in the current gear and just keeps climbing rpms. It will upshift, just not always when it should. I like the shift points, and it shifts great but i will adjust it some to see if it helps i guess. Do those sound like normal shift points though?

Im going to take the cap and have it pressure tested, but after that i will have done almost everything possible to the cooling system with very little improvement to speak of. Im starting to think it may be an engine problem that is causing it to overheat.

I used a hydrometer and the needle floated to about +9, saying that the freezing point of the coolant/water mix is about 10*F. My dad said it sounds like I have too much water and not enough coolant and thats why my car is overheating. Is that right?

Can a pcv valve cause it to overheat? I replaced mine around when this happened (i actually think it was right before) and the new one is very loud and has a different part # on it (which i suppose doesnt really matter). I bought the new one from autozone, and the parts manager was the one that went and got it for me. Not sure if thats a possible cause but I thought id throw it out there.

I havent checked timing, so i will do this when i get a chance. I dont think this is the issue though because it runs great even under load

Im considering the gauge innaccuracy a possibility, but i wont be able to get my hands on a lazer until monday at least.

napalm368

im going through the exact same thing right now with my 86. i did a few things that did help alot. i bought a brand new radiator cap. the lil tube on my rad where my overflow hose clamps on was cracked loose. i had it welded back together. i flushed the hell out of my system.took my thermostat out. and am running alot more water than antifreeze,with a bottle of water wetter in the mix.my fan is also on all the time as well. im do not have a shroud or air dam,,but they are coming this week.looking into a badass fan. Like the previouse post said,,this heat wave is really hard on the cooloing system. i drive at night with no issues. barely go above 210. but full day,,i hit around 240 after about an hour. oh,,and my car was sitting too before i took it over,,there was crud in overflow,that was blocking the hose so i cleaned it all out real good. these things all helped me out a good bit. good luck.

Black88Z

I havent flushed the system yet, id like to asap though. But i still have the problem, but it takes considerably longer to get to 220+. Im going to check timing soon, hopefully tomorrow.

I did notice something, but im not sure if this would actually be the problem or not. I noticed that my a/c condensor is sitting crooked, so rather than being parallel with the radiator its about 1/2in or so away from the rad. on the right side (standing in front of car) and about 2-3in away from it on the left side. Could this actually cause a problem??

Black88Z

355sleeper

iTrader: (4)

Look at my thread i posted in the cooling section, you dont have enough fan.

Black88Z

I read it. I think its something to do with fan as well, but im not positive. The fans are hardwired tho, so i guess its just not pulling enough air. Im going to figure out a way to get the condensor and rad as close as possible, i could kinda see that causing an issue - one side is pulling enough air thru but the other side may not be pulling enough. Either way, i dont see it hurting any so i plan to fix it.

Im also going to check/adjust timing.

355sleeper

iTrader: (4)

Thats what i meant by your fans, the fans arent big enough. I can stand 3ft away from the car and feel the fans pulling through the thick griffin radiator. You are having difficulty pulling the air through yours to cool. Also try pulling the tstat

bowtie1983ss

I had the same trouble for 10 years. I did it all... Finally broke down and put a 2 row BE COOL Radiator in it with their dual electric fans.... BAM! She runs under 220 idling for an hour in stop and go traffic on a 105° day with the A/C blowing cold! I kid you not... I should have done that bigger radiator 10 years ago!

bowtie1983ss

Oh... and you have to put a Fan Switch in the passenger side head to turn the fans on at 195° instead of the factory 230°... yeah...that factory one is stupid. Summit Sells a JET fan switch as P/N JET-60600. On' at 195° and off at 185°

Stevolwevol

iTrader: (1)

Sounds like your radiator was not 100%

karl's-92'-z28

iTrader: (5)

You can try changing your fans or put 2 more on the outside of thr rad & condensor, but make sure its pushing air through & not pulling. Or even changing your fan motors, they may be worn out & not working properly.

naf

iTrader: (7)

If it's not boiling over, it's not overheating. You say you haven't lost any coolant, so...

Your guage is likely highly inaccurate (like all of them) and 220 isn't too high, anyway.

Your two fans are adequate for a factory system that has been well maintained. Do a flush once a year as routine maintenance and clean the radiator/condenser.

Your condenser space from the radiator isn't be an issue for the cooling system. If it's too far away, for whatever reason, the AC system may not perform well as air could be bypassing the condenser. If it's farther away it's passing less heat onto the radiator with AC operating.

Wire your fans back up to a temp switch. Either back to the factory switch or an aftermarket one. Let it idle in the driveway past where you think it's too hot, does it ever boil over? It should warm up to fan turn on temp then cool down to fan turn off temp, cycling like this indefinitely.

Plain water is actually a better coolant than a water/antifreeze mix. The antifreeze provides protection from freezing by lowering the freezing point of water. It also provides pH adjustment to reduce corrosion in the cooling system. The pressurized system increases the boiling point of the water so that it will stay liquid above 212. When it boils over either the system isn't maintaining adequate pressure or the temps exceed the design pressure.

Water wetter reduces surface tension of water and helps reduce cavitation, which a stock system shouldn't be experiencing. It does nothing for the cooling capability of the fluid.

cuisinartvette

great advice. Pull the radiator hold that sucker over your head and try and see daylight through it bet youll be shocked at how much stuff is stuck in the fins.

This will absolutely make a difference promise!!

Then once the rad. is out do something similar to the condenser if you can in car
Hard wiring the fans is a waste and wears them out. There is no need for a fan to run til the thermostat has been opened and temp has gone up another 15 deg. I always run a 160 stat(in a warm climate) fans come on around 185 ish.
Use a GOOD fan. Once the temp is way up there you get "heat soak" and its harder to bring the temps down than it would say if the car was 20 deg cooler.

Black88Z

I should probably start out by saying I am still having the problem, but it isnt as hot lately so ive been able to manage. Still would like to fix tho.

Id love to get a be cool rad, just dont have the money for it right now. How many rows do stock rads have? Would any be cool rad from any year f-body work ok?

The fans do pull air, and they pull pretty strong too. My condensor is pretty chewed up, im looking for another. Maybe thats my problem!

Ill have it flushed soon, but I cant get it flushed for about another month or so..

naf

iTrader: (7)

The stock radiator is more than adequate, however if your 20+ year old radiator is crudded up inside it's efficiency has declined. If this is the case, a stock replacement can be had for ~$100.

You can complete a good flush of the system within an hour, easily. Ensure you flush the block (preferably from the top through the drain holes in the bottom), the heater core (through the heater hoses) and the radiator. Flush until the water runs clear. Use a 50/50 mix to prevent corrosion. You can drill a small steam hole in the t-stat to prevent air pockets from forming beneath it on re-fill.

TreeFiddy

This is probably something that it often overlooked. Obviously if the condensor fins are crushed or blocked, the airflow has a harder time getting to the rad.

Have you actually had any boiling or signs of engine stress (lack of power, surging etc), or is it still just the higher than usual temp readings making you uncomfortable?

Stevolwevol

iTrader: (1)

Also leaves can collect between these which can block air flow. I cleaned a bunch out myself.

Black88Z

I checked the timing (it was warmed up) and with the esc plugged in it was close to 16* at idle and with unplugged it was 4-6 I think (my timing tab is nearly impossible to read, but it looked like it was 6)

Is it supposed to be that high?? Maybe I am wrong, but I thought at idle it should still be at or close to 6....


Could a vac leak at the egr cause it to overheat or advance the timing for some reason? Because my hard line that goes to the egr broke, but i put a soft line over the broken part but it doesnt look like it fits well; im able to move the broken line in or out very easily. Ill fix this anyways of course, just wondering if that could be causing an issue.

Ive been getting a code 42 also, could that be related? (figured id ask)

----------------------------

Treefiddy: I had boiling a while ago i believe, but that was because i had way to much water. Ive added more coolant and i havent had it boil, but it still gets too hot. Id like too see it stay close to 180-185. When it gets too 220 I get uncomfortable, and it always keeps climbing. I never let it get too high, but ive never noticed a lack in power or anything like that either.

Stevolwevol: I checked that and cleaned it out, helped but didnt fix it.

naf: I will be getting it flushed soon, but it'll be mid-august before I can (I can do it at school for dirt cheap).

Stevolwevol

iTrader: (1)

With out reading the whole thread, did you replace the water pump? I still think your temp sensor, or your gauge may be giving false reading.

BlueWrath92

iTrader: (1)

I replaced my entire cooling system including waterpump to find out a bad EGR valve was causing my car to heat up.

Stevolwevol

iTrader: (1)

I didn't know the EGR could cause this. I remember a couple of other threads where someone had mystery overheating issues, and this may very well be why. This is good to know. Sorry it had to be at your expense.

RBob

iTrader: (1)

This can cause issues. The air being a fluid with the condenser being a restriction, I'd bet that the air is being pushed sideways. Not going straight through. Where the air goes from this I can't say. But it won't be going evenly through the radiator.

Yes, at idle 16* BTDC is normal (with timing under ECM control).

Yes, it may be. This is also dependent upon which ignition control module (ICM) is in place. The reason is that late ignition timing dumps a lot of heat into the engine. When code 42 is active the ECM relinquishes control of the spark timing. A properly operating GM ICM will use 'limp mode' advance to help in this regard.

But it still won't be right.

And many aftermarket ICMs won't add limp mode advance at all. So the engine runs with reduced spark timing that causes a lot of heat to be dumped into the engine. At the same time, a loss of power is felt.

RBob.

Black88Z

I can definetly feel it when its in limp mode, it feels like a v6. It does it sometimes when the ses light isnt even on! Could that be the icm? Im not sure if its oem or aftermarket, ill check. I did have it tested at autozone about 20x (no joke) and it passed everytime.

Im going out to fix the egr leak right now

Im still getting code 42 and to be honest its innoying as hell because it comes on at random times, will come on and go off sometimes, and ive checked everything i can think of and found nothing. Could the egr leak be causing it??

Are there any shrouds out there that are better than the stock one? (or lack of one)

RBob

iTrader: (1)

To the first question/statement, yes, when code 42 is active, and with some cals, if it was active and now isn't, the spark advance is in limp mode.

Check the wiring between the distributor and ECM. Also, only use real GM ignition modules. I pull them from JY distributors.

One check is to: warm up the engine, unplug the EST/BYPASS connector, connect a timing light, start the engine and check the timing.

A TPI should be at 6* BTDC. Now, while observing the spark timing via the light, slowly increase the engines speed. About 1400 - 1600 RPM the spark advance (SA) should jump up about 12 - 16 degrees. That is the limp mode SA.

RBob.

Black88Z

I already checked the timing and those were the results lol but thanks for the tip.

The code 42 is very intermittent though, its not a constant thing. It usually does come on every day or every couple days a couple times to bug me, but goes away the next time i start it; its not constantly on.

Next time at at the 'yard ill pull a couple if I can and get them tested. If I get one that passes ill probably throw it in to see if my 42 goes away and stays away.

I believe i fixed the egr problem, its very hard to get to the point it broke at but i think i got the rubber line over both parts well enough. Ill ride it a little harder than i normally do to work to see if it still gets too warm. I am also going to keep an eye out for the temp gauge at the junkyard (probably garbage to tho, worth a shot) and temp sensor. Where is the temp sensor on these cars?

Is it possible for a knock sensor to give a code 42?

samiam91RS

IIRC i had a code 42 and it was a knock sensor issue. they are year AND engine specific so make sure you get the correct one if you replace it. also, don't drop it because it could damage it.
be ready to refill on coolant if you take the knock sensor out though. because the sensor is screwed into a water jacket. best way to get it is from under the car, its next to the starter, on the block where it meets the oil pan.

Black88Z

I was thinking that was a possibility. I just changed the plugs before i had the problem and its a very intermittant thing like a lose ground, so maybe i knocked the connector a bit lose or something. Ill check it out when i do my oil change in the next few days and let you all know how it goes.

Black88Z

I still havent had a chance to change the knock sensor! I have been working alot, no time to yet. But, a few things have changed since my last post

I did some research and realized my car is MISSING its air dam. Im looking into one now. Somebody had brought up an interesting point, are there any being made that look more like the ones used in the 60-70s? More slanted, better airflow, less resistance, more aggressive looking. Is there a way to make one that way? Id be very interested in that!

Since this morning when i started it, the ses light is now ALWAYS on. Ive tried starting it several times thinking it may go off like in the past but it didnt. Still gives me 36 & 42, which are both codes for faults in direct injection system and fault in EST circuit. Im also getting 51, but this doesnt seem to be every time. So im a little confused as to where to even start looking!

Recently when the ses light would come on, the car would have a miss/stumble that was noticeable around 2k+, it got slightly worse the higher the rpms got. Somebody broke the tabs that hold the connectors to the injectors, so i thought maybe one wiggled loose or something (long shot I know!) so I would push them all down, push the est cable snugly together and the esc, and start it back up and the problem was gone. I did this a few times and it seemed to work. Now thats its constantly on, it hasnt worked yet lol. I dont have the miss/stumble anymore, and odly enough the car still runs pretty good. ALMOST as good as noral, just not quite as good. Managed to break loose on accident going to work, and I didnt even step on it lol I was really surprised, it still is running strong.

Yesterday at a light I was stopped and the car was idling fine, then it dropped off and almost stalled out, then came back up-SES light on. Ran crappy again. Got where i was going, an hr later started it back up and it was still on, and ran bad. It went off later that night though, only to come back on this morning.

I have noticed that when i shut off my car, the temp gauge acts a little weird. Rather than going down to the bottom, or even staying still, it goes up! If the car is on and the gauge reads 220, when i shut it off it goes all the way up to 3/4. I dont think this is normal, is it?? Or is this an indication of a faulty temp gauge/ sending unit?

Thanks guys, this is really irritating me but I appreciate all the help. The worst problem is a problem you arent sure what it is! lol

musicfreako

iTrader: (1)

My car will overheat with with no air dam every time! Thats your problem. Stock works just fine.

Black88Z

Ok, thanks. Im still going to look for an older-style looking one because i think itll look better lol but how long does it usually take to overheat? (if its roughly 90* out)

Do you have any input on my ses codes or other problems?


Little update, I went out to ohm my injectors, they are all cold but ohmed out low-mid 17's, all fine. I will ohm them hot tomorrow morning. What is weird is when I started it up after ohming them, no ses light. started it 3 times and no light any time. Warmed up to about 130-140 too. Its late, so i didnt rev it very high but gave it a few blips to about 12/1500 and it revved fine. I should mention that I did also unplug-reconnect the est line. I didnt touch the ESC this time though. Not sure if the ses light is gone because of what I did or if its just acting weird on me again!

naf

iTrader: (7)

Everytime you unplug the ESC it will trip and store the EST trouble code. You need to clear the codes after each reading.

The wavy thing in your dash that you refer to as a 'temp guage' is no actual indication of the state of nature at the end of its sensor, and when you shut the engine off it's going to do whatever it wants to. Don't worry about the 'temp guage'. If you're concerned about the actual temperature of your coolant, use some other yardstick.

As cheap as a set of injectors are it may be worthwhile to replace them vs trying to get yours cleaned.