TexasLT1

ok, Ive got a '95 LT1 in a '92 RS. a few months ago my temp guage on the dash quit working, turns out I needed a new connector for the temp. sender. ever since I fixed the guage, it seems to be running hot, there was one day it started approaching the red. I have the fan wired to be on if the key is on, so I know that works. I had a 180 thermostat in it but I pulled that out. I just replaced the waterpump yesterday, the old one had some trash or something in it and it wasnt pushing any water out. Im not blowing white smoke, no coolant in the oil. what the hell is going on? Im about ready to push the damn thing off in the lake and be done with it. just today, I pulled the thermostat back out on the new pump, started it up, ran about 130, very slowly climbed up to about 150 after a few minutes just sitting in the drive way. started down the road at about 15 mph, then turnded out onto the highway, got up to about 70, drove for maybe a mile and a half, stopped, turned around, guage was just over 220. got back home, guage was at about 230. released the pressure on the cap, popped the radiator cap, stuck a thermometer in and it went off the scale on the thermometer at just over 190. so something is completely screwed. any ideas?

SpeedCat86

Since the water temperature sensor is in the block/heads, and not the radiator, it is going to read a little hotter that a thermometer in the rad tank. Keep in mind that 220 is not all that hot for a pressurized, glycol mixture. It is a fine line between warmed up and over heated though.......

I'm guessing you aren't running any thermostat, right? If so, your car will take longer to get 'warmed up' because the radiator is in the cooling loop from the start. It will appear to run cooler, longer before getting hot.

Check your lower radiator hose to see if it is collapsing. Get the car warm, and have someone rev the motor while you watch the hose. If it does, get a new one, preferably with a wire stiffener in it. The collapsing hose could also indicate blockages in your radiatior.
Take off the cap and look inside the tank. You may have to let some coolant out to get a good look at the tubes in the radiator. Do they look fairly sharp and clean or do they look calcified and fossilized like a coral reef? You said your water pump had junk in it. Those deposits are the minerals from the water you used in the cooling system. I know it seems snobby, but when you fill the system, get a couple of gallons of the cheap spring water from the supermarket and use that instead of sticking your garden hose in the radiator. I personally don't even like using Norfolk City water to wash the car, there's so much stuff in it, let alone put it in the radiator.

I have struggled for the four year I have owned this car, untill I stuck a new radiator in it a couple months back. For the money, it was a great improvement. I have a stock style radiatior with aluminum fins, a modified 195 degree 'stat, and even after four runs on the autocross circuit, (which will over heat a car better than anything), the water temp was a mild 215.

These cars can be made to run cool, don't give up!

TexasLT1

well I guess I should have included more details. I replaced both hoses about a month ago with goodyear wire stiffened hoses, the radiator, pump, and inside of the block were all perfectly clean, the piece of "trash" was a piece of old silicone that was stuck between the front face of the impeller and the front cover of the pump. I just got back in from trying something else. we pulled the cap, started the car, loosened the outlet hose, had plenty of flow, so I know its pushing water. stuck the thermometer in the radiator, started reading about 170, after 5-10 minutes of running like this, the thermometer read about 200, dash guage read 260. Im going to autozone today to get an aftermarket guage to replace the dash guage sender and see what that does. is there anyway to figure out if a head gasket is blown? when we had the cap off, there was one point where there were very small air bubbles in the coolant and it looked almost like there were real small black particles. but when the bubbles went away, so did any particles. what the hell is the deal?

SpeedCat86

Sounds like your gauge is on the fritz.

dunno about the air bubbles and little black spots tho....

I wouldn't worry too much about air bubbles, as there is bound to be some air trapped somewhere in the system.

I'm drawing a blank on 'tiny black spots' they could be anything.........

TexasLT1

well, it appears that it was the guage. when I hooked up the aftermarket one, it got up to 235 at one point, but that was with it at about 1800 rpm sitting in the driveway. so thats kinda to be expected I guess. I slowed it down to about 1400 rpm and set an old furnace blower motor in front of the car to get simulated highway airflow going into the radiator (it puts out a LOT of air, probably equal to about 35-40 mph) and the highest it got was about 215. not too bad. my dad just left to go get a tee so that we can hook the dash guage back up and run them both at the same time just to make sure. thanks for your help and time though.

tristan

SpeedCat86

Glad to be of some assistance. That's what we're here for.

TexasLT1

well it appears my troubles arent over. this morning we hooked the dash guage back up, and pulled out the a/c condeser because I realized hardly any air was coming through the condenser and the radiator. pulled it out, let the car idle for almost 25 minutes, temp only got up to about 150 with the fan in front of the car. took it out on the highway, drove about 60 for about a mile and turned around, by the time I got back to my road, guage was reading 235, when I got to my house, 1/2 mile down a slow road at about 15, guage was up to 240. I checked all of the driverside plugs and they all look good, no washout or anything, so I doubt its the head gaskets. we think the radiator out of my brothers car might fit so we are going to try that tomorrow. any other ideas?

88ROC1LE

iTrader: (4)

You are getting good coolant circulation right? You have covered just about every aspect of coolant flow outside the motor between the radiator and the heater core. I also see the hoses should be in good shape, so I believe it may be a circulation problem, just a guess and trying to throw out some ideas for you. Untill you figure it out though be carefull letting it get too hot, don't want to damage anything unnecessarily!!!!

TexasLT1

well, I feel like a jacka$$ now, it seems that all of my problems stemmed from too high a ratio of antifreeze to water. we flushed out some of the coolant and added more water to it, and it seems to be fine, I havent driven it on the road yet, but i let it idle forever and the temp never rose above 180. and that was without the fan in front of the car. so....it appears everything is fine again. we'll see.

TexasLT1

ok, this is really pissing me off. Ive gone through my whole friggen cooling system and the damn thing is still getting hot. on my way home tonight it go up to 250. WHAT IS GOING ON?!?!? I guess tomorrow I'll take it and have it professionally flushed out and cleaned and see if that does anything. the only thing left to do is replace the radiator. anyone used the aluminum single core from autozone?

steve8586iroc

Will the engine cool back down if you stop and let it idle with the fan running? Sounds like you may not be getting enough air thru the rad while driving on the road. Check your chin spoiler below the radiator. If it will idle for long periods of time without over heating then check the chin spoiler. You could also have a restriction in the block somewhere. Are both gauges saying it hot or just the factory one?

Steve

TexasLT1

well, I guess my first question is what is there to check with the chin spoiler (air dam?) its either there or its not. in my case its there and still seems to be in good condition. yeah, I can idle forever if I wanted to, probably wouldnt go above 190. if I drive it, then park and leave it running, it cools back down, somewhere below 210, maybe about 190. both guages were showing it getting hot, the dash guage just did it sooner than the aftermarket one, so I know my dash one is messed up somehow, just dont know what caused it. Im going to try some of that water wetter stuff, of something like it, and see what happens. I considered a restriction in the block, but I just dont see what could have caused it to just happen all of a sudden.

steve8586iroc

One other thing I thought about today is timing. If it is too retarded for some reason it can cause the engine to run hot. But as thorough as you seem to be in all regards I dought it's your problem. Just a thought.

Steve

TexasLT1

steve, two things.

1. thanks for your comment, I'll take that as a compliment
2. timing for the LT1 is controlled by the computer, so there is no way thats off unless there is some other problem that would make it adjust it.

but I thought about something else today. could the engine running rich cause this? I would think that rich would semi-cool it while lean would make it run hotter. I know its running really rich because:

1. I can smell it
2. the gas mileage has gone to ****
3. the power level in general seems to be down
4. I have some really nasty exhaust leaks.

I think I may have bent the y-pipe or something. I was jacking the car under the crossmember, and the p.o.s. heddman y-pipe is very close to it, and after I already had the car at the top of the front suspension did I realize that the y-pipe was on the jack too. Im going to try and fix that tomorrow because its really bad and I cant take it anymore. lately everything has been pissing me off. but I know that if I get one thing fixed the rest of the problems wont last much longer either, Im just trying to find a place to start.

the last thing Im going to try before replacing the radiator is completely flushing the entire system. today I used this stuff called Stops Overheating that we have at Autozone, it seemed to help a little bit. it still got up to 245, but it seemed to take longer to get there. although that may have been that it was also at about 9:00 at night instead of noon, so nevermind.

any other ideas? PLEEAAASSSEEE!!!! its killing me!

TexasLT1

anyone......?

TexasLT1

ok, today I flushed the system twice, put a brand new LT1 thermostat in from the dealership, filled it COMPLETELY full of straight water, and it is still getting up to 240 within about 5 minutes of driving it. if anyone would like to help out here, now would be a good time.

steve8586iroc

Texas, how does the circulation look with the radiator cap off and idleing and then with it, at say 2000 to 2500rpm? Then does it over flow if you release the throttle real quick? It still looks like a restriction in the block. Is this a stock LT1 with a cam driven pump? Just wondering if you've had the heads off and replace the head gaskets.I hope you can get it fixed before to long, I know it must be a real pain to figure out. You might also try asking the guys over at Z28.com if they have any ideas sense most of them have LT1s.

Steve

TexasLT1

well, the circulation looks good at idle, tried it at about 1500, but havent tried it at anything higher, guess I'll do that tomorrow morning. its still the stock cam driven pump, but I have had the heads off, pulled them a while back because I blew a head gasket. Im going to pull the valve covers tomorrow also and check all of the head bolts, make sure none of them have backed out a little. I hope like hell its not a restriction in the block, I dont know how I would solve something like that. today my dad was looking through the chiltons and he asked me a question I didnt know the answer to, did I know there was an arrow pointing forward on the head gaskets. I dont think I ever considered anything like that, and Im going kick my own *** if thats it.

jmd

iTrader: (4)

If the radiator is original, get a new one. Don't even ask why.

if you see corrosion around the tubes at the inlet on the rad., the corrosion around the tubes down low is even worse!

You're having either air or coolant flow issues at speed; the lower air deflector on the core support is very important, and if you have blockage in water flow (I read kinda fast but didn't see you replace the rad.?) you'll have problems at speed that you won't at idle.

The one row Modine 951 should be fine. A friend is using a used 2 or 3 row brass/copper replacement rad. out of an 86 Iroc with a 95 LT1 in a g-body; no problems. In my experience, the one row alum. outperforms the brass/copper ones.

Matthew

TexasLT1

jmd, I replaced the radiator about 6 months after I bought the car, so about a yeah and a half ago. the inside is almost perfect, no corrosion or anything.

well, Im beginning to think its a cracked head. I dont have time to explain right now, but I will later tonight.

SSC

Thats not hot considering a thermostat "the correct 195*" is supposed to be fully opened @ 222* and its not abnormal to run 230ish just not desirable for a performance engine.

TexasLT1

SSC, we put a 180 in to try and cool it down some. but it has still gotten up to 240, which is too hot for any engine.

like I said, when Ive got time tonight I'll explain whats going on now. some new things have come up

TexasLT1

ok, lets see. we put the 180 therm. in the other day, didnt seem to make much difference at first. we filled it with straight water because we were tired of buying antifreeze. car still got to 240 after about 10 minutes of normal driving, about 5 if I got on it. if I let it idle, it would take about 20 minutes, but it would still get up to about 200-205. well, we pulled the line coming off the throttle body, bypassed it, and shoved an air line into the end of it. then we popped the radiator cap and let about 50 psi air go through the entire cooling system. then, we put the cap back on, pulled the temp. sender, and did the same thing. we reconnected all of the lines, refilled it with water, left the throttle body bypassed. and started it up. I let it idle for probably 30 minutes, temp never rose above 170, even with the 180 thermostat in. I jumped in, and drove it down the street about 2 blocks, turned and drove another block, then turned back and drove the 2 blocks back. the whole time, the temp never went above about 170-180. just before I turned back for the shop, as I left the intersection I just nailed it, hit the shift light in 1-3 gears. slowed it down in 4th, then turned into the shop. within about 20 seconds of leaving the intersection, the temperature rose from about 170 to almost 220. so I knew something was wrong, I pulled back into the shop, let it idle for another....10 minutes, temp only went down to about 205. ok, so this is one reason I think I have a cracked head. our thinking is that under normal driving conditions (anything under about 2500 rpm) the cylinder pressures are low enough that any pressure cant leak out through the crack. but as the rpm gets close to redline, the cylinder pressure gets high enough to push out through the crack, but the crack is small enough to keep water from coming back through it. another reason we think it is the heads is because there are very distinct air bubbles coming into the radiator from the coolant line coming from the back of the heads. the last reason we believe its a cracked head is that last november I badly blew both head gaskets, to the point that I couldnt even turn the engine over due to water lock. at the time a visual inspection of the heads didnt show anything wrong, and we didnt think it had gotten hot enough at the time to do any damage. so....now Im on a search for heads. Im thinking about the AFR Stage 1 LT1 heads from Excessive Motorsports. havent made a discision yet. plus I wanted to verify our thinking with other people before we shelled out $1500. anyone else think we're correct?

TexasLT1

somebody's got to have an idea...

bigbrianiroc-z

LT1, afr heads are great and 1500 sounds about right. also for your over heating try some water wetter or some royal purple purple ice, they work great when u dont have to much antifreeze in there.

mystikkal_69

iTrader: (2)

i know the LT1 has bleeder screws. did you properly bleed it? i had a shop "professionally flush" the cooling system on my 94' and it started to overheat on me(it never did before). i read up on the LT1 and saw it had bleeder screws. i bled it and voila. it works as it should. there was quite a bit of air trapped in the system. what fan setup are you running? the single electric fan?

RODS92Z

Check your oil and see if theres antifreeze in it. Rev ingine while someone watches the hoses to see if they collapse. My car was doing the same thing would idle fine but would get over 230 while driving. The top radiator hose was collapsing, only under load. FIrst I changed everything that could be a problem except the hoses. Damn hose!

TexasLT1

RODS92Z, thanks for the tip, but if you would have read the whole post you would know that that was about the very first thing I checked and replaced.

anyway, Ive tried stuff similar to water wetter, bled the entire system numerous times, completely flushed it 3 times, all with the same outcome. the heads will be here in 2-3 weeks. already ordered them, because there is absolutely nothing else that could be wrong.

RODS92Z

Yeah I just kinda skimmed thru the thread. If everything has been gone thru then I would say its one of your heads. Does it smoke at all? Since your taking off the heads check your cylinder walls thoroughly for any hair line cracks. Have you driven it with the heater on? What did it do? Was there heat coming thru the vents? I found the best way to add coolant is to have the heater on so you can get full circulation and get all the air bubbles out.

Nails

If you think you have a cracked head did you try a leak down
tester? If you had a cracked head on any of the holes you should
see bubbles in rad. When you say it heats up only driving and
not idling could that be a plugged cat? Hope you find it, just my
2 cents

Nails

btw do you have a auto or manual? if you have a auto check
the temp, level, quality of the oil. where you are at I would
get a serperate tranny cooler not the one thats hooked to
the rad. Thats if you have a auto.

BONES LB9

i thought lt1's came with 160* stats from the factory? there's a tool that came detect if u have head gasket problem. u run the car till the thermostat opens hold it around 2000rpms. the tools like a turkey basser u squeeze it, it sucks up the fumes from the radiator and if it turns yellow u have a head gasket leak but i don't know where u can get though.

TexasLT1

RODS92Z, yeah its cool, I wasnt in a good mood when I checked the post then anyway. well, I have no smoke at all, but there are still bubbles in the radiator. no heater either, one of the hoses that connectes to the fittings on the the firewall cracked a while back, and since it gets hot enough down here in the summer to cook food on the hood, we just bypassed the heater.

Nails, isnt a leak down tester the one that you pull a sparkplug and screw into the hole? if so, thats the reason I havent done it, with headers and such a tight engine bay, we'd have to pull the engine anyway just to be able to hook the damn thing up. and yes, I am getting bubbles, so thats what finally led us to that decision. and I have a manual transmission, so no cooler. also, the cat was gutted when I bought the car, so no plugged cat either.

BONES LB9, nah the LT1's came with a 180, I dont think any factory cars have a 160 in them. I havent heard of the tool you're talking about, but I will check into it.

thanks for the info guys. I hoped at first that it wasnt the heads (or head) that was the problem, but now Im kinda glad it is because I can finally get some good aftermarket heads on it. thanks for all the help, I'll keep it updated once I pull them off and see what it was.

egmonster

Hehe. You basically figured this one out on your own. Sometimes it's always nice to have ap lace to rant though eh?

egmonster

Well I think you've figured it out at least .

Desert86Roc

One thing you posted sounded real familiar. I too experienced the cool at idle then when you stomp on it temp spike up past 220. I too, bypassed my heater core (dont need it here in AZ very often) because it was leaking. I found that I began to run hotter because the hot coolant from the intake manifold was piped directly to the "cool" side of the radiator. Water takes the path of least resistance, so there was more flow actually bypassing the radiator than was going through it. So instead of cooling... the fluid would progressively get hotter and hotter to the point where the little bit that did go through the radiator did not do any good.

As soon as I noticed this, and blocked the radiator and intake ports with plugs, the radiator was then able to get full flow again, and the temps went down.

Any easy solution to try before you tear your engine down.

TexasLT1

Desert86Roc, thanks for the info. but what do you mean when you say you "blocked the radiator and intake ports with plugs"? right now Im willing to try anything before I pull the engine. but then engine is coming out anyway because the heads have already been ordered and are on their way. but its going to be a while now before I can do anything because I pulled my tranny on friday to rebuild it, turns out I need a new output shaft, so its going to be a few days before I even get it running again.

Desert86Roc

Normally, you have a heater hose (or TB hose) coming out of the front of the intake manifold, and ends up going to the heater core. You bypassed the heater core, so I am assuming you went straight to the radiator instead. Take the hose out. Put a brass plug (or anodized aluminum if you want to get fancy, like me) at the manifold. Put a rubber block-off plug at the radiator. Pics below.

Manifold Plug

or


Radiator Plug

TexasLT1

Desert86Roc, thanks for the tip, but thats basically what I have already done. on the LT1, the heater hoses come out of the water pump, so what we did was just curve it back around right back to the pump.

Desert86Roc

Sorry, wasnt aware the LTI was set up like that. Have you considered an engine oil cooler to get that extra cooling help our locations need (TX, AZ)?

TexasLT1

ok, Im ready to push my car off into the gulf and let the fish have it. I ordered AFR heads through Excessive Motorsports. something messed up with them, cancelled the order. Ordered LT4 heads and intake from GMPP, got the engine back together 2 days ago, got it running yesterday afternoon. turns out, the damn things overheats worse and faster now than it did before. plus, I got my scan tool working again, dash guage showed 240, scan tool showed 220. what gives? hooked up mechanical guage, verified dash guage. something is not right. we checked the old heads, werent cracked. only thing left is the block. someone please give me ANY ideas before I pull the engine again. I leave for school in 2 and 1/2 weeks, Id rather not be working on my car the whole time.

TexasLT1

I was just thinking about something, the new heads didnt come with any plugs or anything for the coolant passages, the LT1 heads have a coolant crossover on the back of the heads that connect the two, and this line runs forward to the radiator. since both heads are identical, there are holes in the "front" of the heads for this crossover. we put some plugs in that we had laying around that happened to be the right size because we couldnt get the ones out of the old heads. if these plugs stuck in too far into the coolant passage, could this cause a restriction of the coolant, increasing the temperatures like its doing?

camaroguy99

Ok this may sound stupid and I'm a little recultant to say that I did this but...

How do you have your fan wired? Make sure it is pulling air and not pushing air. I had the same problem that you had when I hooked the wires to a manual switch. I went through just about the same process as you, swaped out every part of the cooling system, turns out I reversed the wires to the fan so it turned in the oppiset direction. So when I was at speed the effective flow of air through the radiator was close to 0. When I came to a stop or idle, the fan was pushing enough air to keep the car cool. Switched them back and no more problems!! Good Luck.

Jim

TexasLT1

I know the fan is pulling air, I havent touched the factory wiring, we just grounded the relay to turn the fan on at all times. but it was overheating even at idle, so it wouldnt matter which way the fan was turning.

Nails

sounds like you may have to get one of those big alumminum
aftermarket rads and possibly use a mechanical fan and shroud
if possible or at least a good dual fan setup with shrouding.
I noticed on your website that you have headers and a open
air element under the hood which looked like it would draw
in hot under hood air which probably doesn't help. You should
take the hood off and drive around and see what happens
just to experiment. I can only imagine how hot it gets there
here i western canada it got to mid 90's last week and i noticed my 87camaro getting pretty warm when sitting at lights. GM did
a crappy job for the cooling on these cars. Large engine in tight
engine bay should have made a better cooling system. Anyways
hope you beat it

Matthew91-Z28

I feel your pain..I drive a 91 Z28 convert and have had heating probs since the weather started getting hot. Sounds like your prob is very unique. And there are a few things that point to a cracked head like you observed. One other little thing that may help if its not the heads. There were alot of posts and I'm not sure if you said you'd replaced the fan switch or not. Guessing you have dual fans. I do. I replaced the fan switch with one that turns on at a lower temp. It has helped alot.....but I'm still trying to cool it down. I've got a aluminum hi-flow water pump in the mail and hoping that will cure my prob.

Any way...its frustrating as hell. I know. And I grind my teeth when I get stuck in traffic ...hoping she won't boil over.

And you say you have been driving it with just water in it lately....testing it?

bigbrianiroc-z

i dont know if im right or not but i think that like 212 or sumthin around there is the op[timal running temp for computer controlled cars so ur not to far off. i live around houston so i know how the heating thing goes and i hope u can get it figured out.

TexasLT1

well, first off, no I'm only running a single fan. the original engine was a 305 TBI so thats all its got. I think I said it somewhere before but I dont remember, Ive got the fan relay grounded so that the fan is on at all times, so its not a matter of it kicking on early or late or anything.

as far as the straight water, yeah that was only for about a week because we were trying stuff so often we got tired of wasting money on antifreeze that would just end up on the ground in a few days anyway.

I pulled the intake manifold back of today in anticipation of pulling the heads tomorrow. I stopped that far today in case I found out anything useful on here and camaroZ28 before I completely tore the engine back down.

it just makes absolutely no sense! there has been NO oil in the water and vice versa, I would think if it were a cracked block/head or a head gasket it would be obvious. if I pull the heads off, find nothing, put them back on, and it still does it, the car is getting parked until I get back from school in December. Im simply not going to screw with it till the day I leave for no reason. in fact, I might even make someone a good deal on it... just kidding, its just frustrating as hell not knowing what it is.

one thing we are doing this time that we havent before is we are getting the head and intake gaskets and the head bolts from GM just to make sure we get the right ones, and we are going to try spray painting the head gaskets silver just to make sure. Ive heard that from a number of people now so Im trying anything I hear.

and one more thing, when sitting at idle, what effect on the temperature would not having the thermostat in have? Imt rying to figure out if its anything we've done during our screwing around with it that might have caused this, or atleast given us faulty info during some of the testing.

TexasLT1

ttt

steve8586iroc

LT, just to suggest something you might have allready tried. You stated in earlier post that you just looped a hose from one hose nipple on the water pump to another. Are you sure this is not allowing water to just recirculate in the pump and not actually pumpimg it through the block? This might keep the engine somewhat cool or stable at low rpm but not at higher rpm where the engne makes more heat. You might try to cap off those nipples on the pump. Just a thought.

Steve