mystery overheating

[leggomieggo10]

i recently picked up a cheap 92 sl that needed a 60, timing jumped 3 teeth, no damage.
did my 60 k, car runs beautiful. but its overheating if i drive on the interstate for about 5-10 min. itll drive all day long through the town an wont overheat. but as soon as i start on the interstate about 5-10 min later the temp starts creeping up. turning on the heat doesnt help at all. its got a new water pump, tstat an fresh coolant, new rad cap as well. my fans are wired so i know there on for a fact. why would my car overheat after driving on the interstate?? if it was a clogged radiator it would be overheating no matter what.

is the trans temp hooked to same gauge???

[Alex3000gt]

Are the fans pulling, or is polarity switched and they are pushing?

Warm up the car, keel it running and pop the hood. Use a piece of paper to see if the fan is truly pulling.

Do both fans come on?

[x2xtreme360]

if it was a clogged radiator it would be overheating no matter what.

Not necessarily. A semi-clogged radiator can definitely cause your issue.


Headgasket.

Steve

Did he say anything remotely close in his post that pointed to a head gasket problem? Why are you still here?

[$$$PIT]

I had the same problem. Turned out I had a leak on one of the O-rings goin' from the water pump to the water neck. It would only leak when I was on the highway. I could drive in town forever. In fact, I drove for 300 miles in town before I took it out on the highway and found the leak the hard way.

[leggomieggo10]

im not losing fluid at all,

its not the the headgasket, ive got good compression an again im not loosing oil, def no oil coolant mix.

an i replaced the oring on the coolant pipe.

so a slightly clogged radiator would cause that problem, weird.

anybody know if the trans is hooked to that temp, its a automatic. i hope my trans isnt overheating

[speedy25]

An AGED radiator is more probably the cause. As they get older the fins detach making heat transfer less efficient. When I got my car it would creep up when I used the AC. When I finally pulled the rad most of the bottom fins were rotted off.

Another overlooked cooling problem is NOT doing a flush after replacing a bad head gasket. Oil in the cooling system will keep heat transfer from happening.

-SP

[leggomieggo10]

i never changed the headgasket, there was never a coolant mixture, im pulling th radiator tmw, i just have a feeling thats not the problem, ive just never seen a rad cause problems only at high speeds after minutes of driving.

how would one check the radiator?? just stick a water hose in it an see how well the flow is
???

[leggomieggo10]

update!!!

alex, i checked the fans they both come on as for the direction they both shpin towards the drivers side, can any confirm this to be correct??

an i pulled the radiator, stuck a water hose in the top an at first it came out a little slow but it may have just taken time to get through the rad, after just a few seconds it came out the bottom in a real nice clear water flow. I than put everything back together an started the car, ran it until it got normal temp, adding water as it got low. im pretty sure the water pump is good, it is new an the water was doing a swirling effect,, once the car got to normal temp the water in the fill neck when down, Im assuming the tstat opened up alowing water to flow. I made a video if it helps, take a look an tell me your thoughts.

when the car got to normal temp the bottom hose was damn hot, like i could only touch it for a a split second before it hurt, but the top hose i could hold my hand on it an it was just kinda warm. Is that normal??

help lol. thanks guys

heres the vid

http://www.youtube.com/watch?v=7DSMJhjw6ec

[leggomieggo10]

alright now im getting pissed off. after all that work, its still overheating, both hoses are hot as hell after driving on the highway,

this is rediculous,i need to know that since it being an automatic, if the trans temp is also on the same gauge, i have a feeling the trans is getting hot

[BaadVR4]

Since the trans fluid is cooled by the engine coolant, any rise in engine temp will cause a rise in trans fluid temp. whether the trans is getting too hot depends on how much the engine is overheating and how long it remains overheated.

[leggomieggo10]

you mean its cooled by the coolant radiator? so a rise in either motor or trans will cause the gauge to rise???

i went an bought a thermal thermometer, here are the readings, please read carefully an compare

ok before i left an the car was idling, everything is in F lol, car gauge was at normal
front head-171
h2o pump-174
rad-120
trans pan-136
trans-157

after being on the interstate an it overheated three times, i took the temps
1st time it overheated car gauge red line was on the thermometer symbol
front head-180
h2o pump-195
rad-180
trans pan-149
trans-152

2nd time it overheated, car gauge same spot
front head-167
h2o pump-188
rad-176
trans pan 140
trans-163

3rd time it overheated lol, car gauge same spot
front head-187
h2o pump-197
rad-180
trans pan-150
trans-180

an after the highway idling in my drive way, when the gauge was almost back to normal (1-2 ticks above normal)
front head-160
h2o pump-180
rad-140
trans pan-122
trans-160

[GTwizard]

That,s a bad radiator. And just feel if the fans blow toward the motor or out the front. bepending on how the fans are bent if they will be clock or counter. With you fans hot wired, they shoulkd be moving a ton of air.

[Alex3000gt]

That,s a bad radiator. And just feel if the fans blow toward the motor or out the front. bepending on how the fans are bent if they will be clock or counter. With you fans hot wired, they shoulkd be moving a ton of air.



My bet is reversed polarity. You can't really 'feel' if air is flowing one way or another, you just feel random air blowing about, haha.

Use a sheet of paper and hold it to the fan, if it sticks - your polarity is reversed.

[leggomieggo10]

can i ask why you think its a bad radiator???

i tried just feeling the air, but with both fans on it just feels like alot of air lol so thats why i said they both spin towards the drivers side,

[Alex3000gt]

can i ask why you think its a bad radiator???

i tried just feeling the air, but with both fans on it just feels like alot of air lol so thats why i said they both spin towards the drivers side,


Use a sheet of paper, hold it to the fan. If it sticks, BAD. If it blows away, GOOD.

Report back results, I can't help you if you don't try these things.

[Deathstrike]

had the same issue in my 93 sl. Idle in the driveway temps are fine, drive it and it would overheat. Tried everything even went to a radiator shop and had it flow tested, changed the rad because nothing else was was fixing it and then it was fixed,it was just old and needed too be replaced

[leggomieggo10]

alex, i stuck a piece of paper down by the fans an both of them pushed the paper towards the engine, so i guess thats right.

does anyone know or sure if you put a manual trans rad in a automatic an than hook up a aftermarket trans cooler?? i dont have money for a new rad but i have a rad from a manual, i could afford a 30 dollar trans cooler. would this work the same?? in theory it should

[speedy25]

your radiator can flow just fine and still be a piece of crap.

-SP

[BaadVR4]

Just because you don't see any fluid on the engine or ground doesn't mean you don't have a leak. Many times the coolant simply evaporates before you see it. I had a car that would never overheat except after 5 or 6 dyno pulls. A year later I find a "pin hole" leak in my Koyo radiator (right by where the AC stud would hit it). Replaced the radiator and went back for tuning after a turbo change. Did 15 pulls, no issues at all. I never saw any water on the ground. Maybe once a month, the temp gauge would start to go up and I'd have to put coolant in the engine, typically about 3 quarts. The coolant had slowly leaked out the pin hole in the radiator and the engine then pulled a small amount of air back in the hole. Eventually, enough air gets in to form an air pocket in the top of the engine and overheating starts. So, even if you don't see any leak and even if the overflow tank level never gets low, you CAN have a leak which causes overheating when the system is stressed.
You can install the manual radiator and use an aftermarket trans cooler, but I wouldn't do that for long. Even the big trans coolers won't cool like the stock radiator tank. Just my .02.

[leggomieggo10]

well its a na, that never goes above 3rpms. i drive it like a sissy.

ive always heard the stock trans coolers are crap. that you should always just go with a aftermarket trans cooler.

i have a extra coolant temp sen im gonna change out today before i do the rad swap

[Alex3000gt]

well its a na, that never goes above 3rpms. i drive it like a sissy.

ive always heard the stock trans coolers are crap. that you should always just go with a aftermarket trans cooler.

i have a extra coolant temp sen im gonna change out today before i do the rad swap


You are correct. The weakness of our automatics are that they run hot, this thins out//cooks the fluid and things start to break. The oil to water cooler exists because it helps bring the trans up to temperature faster, which helps with wear and fuel economy. The downside is that once fully warmed up the trans oil doesn't exchange heat well with already hot coolant.

Some people hook up an external oil cooler in series with the "in tank" (water to oil) cooler - the downside of this is that you increase internal pressure drop and potentially decrease trans oil flow. Running ONLY an external oil cooler isn't the best either because your auto trans will take forever to warm up in cooler temps, and may never reach operating temp in winter.


The best option would be to have the "in tank" cooler and a big external oil cooler in parallel, with a thermal bypass valve to allow oil to switch paths between the "in tank" and external once the trans oil is up to operating temp.

I'm not sure if anyone sells a kit like this, but it would definitely increase trans longevity.


Btw, I design heat exchangers for the largest auto parts supplier on the planet. ;)

[leggomieggo10]

well i live in florida an the weather shouldnt really be a issue, so im gonna go head an install my manual trans rad in it. i just bought a aftermarket trans cooler.

i changed the coolant temp sen with no luck, im waiting for the car to cool so i can swap everything. if this doesnt work im gonna set this bitch on fire an collect insurance

[Alex3000gt]

well i live in florida an the weather shouldnt really be a issue, so im gonna go head an install my manual trans rad in it. i just bought a aftermarket trans cooler.

i changed the coolant temp sen with no luck, im waiting for the car to cool so i can swap everything. if this doesnt work im gonna set this bitch on fire an collect insurance

I'll buy it cheap. I had my Stealth shipped in from Florida.

[Alex3000gt]

well i live in florida an the weather shouldnt really be a issue, so im gonna go head an install my manual trans rad in it. i just bought a aftermarket trans cooler.

i changed the coolant temp sen with no luck, im waiting for the car to cool so i can swap everything. if this doesnt work im gonna set this bitch on fire an collect insurance

Are you losing any coolant? Check the level at cold temp then do a few highway runs, let the car cool down and check it again.

[leggomieggo10]

nope not losing coolant. thats the first thing i checked for.

nope wont sell it, rather watch it burn an get my insurance out of it

[leggomieggo10]

well ive done the swap, im kinda afraid to drive it because if it was the trans overheating, ill never know right??

[Mike-92RT]

i know this has already been discussed, but just to be sure, stick your hand over the exhaust pipe, for 5 or 10 seconds, and smell it. If it has a sweet smell, then your burning coolant.

2nd, is there any noises while your engine is on?.. could be a faulty water pump?

ORRR (i just remembered)

check to see if your thermostat is in the right position.

[leggomieggo10]

if the tstat was facing wrong it wouldnt work at all. i havent lost any coolant in the over 2 weeks ive been driving it. i havent lost any. motor is quiet. water pump is new

[Alex3000gt]

if the tstat was facing wrong it wouldnt work at all. i havent lost any coolant in the over 2 weeks ive been driving it. i havent lost any. motor is quiet. water pump is new


Do you have working AC?

Also, maybe you can measure temps at the oil cooler exit. Where do you have it placed? Try to get it "fresh" air that isn't heat soaked by the radiator exit air and it should kick ass at cooling the oil.

[leggomieggo10]

no ac, an i put the trans cooler in front of the condensor in the big hole in the bumper.so its getting air

this car is def. fucked up.

drove the car got 5 min down the street an it started overheating. but cooled back down like 5 sec later.drove about 10 min at 65 an than 10 min at 75, never overheated. get off the freeway. back in town come to stop light. still not overheated. as soon as i start going it starts to overheat. but than cools down if i let up off the gas. an it continues to overheat after stops but cools if let off the gas

[Alex3000gt]

Remember, when you are on the gas you are generating more horsepower... This means more waste energy (heat) is being dumped into the coolant. Ideally, coolant flow and airflow also increase as you accelerate. Seems you have an issue with one of the two.

1) Try running with no thermostat, if it still overheats that rules out a thermostat issue.

Report back and we can go from there.

[leggomieggo10]

that was my next step. ill have to do it tmw. i have school tmw an got homework.

[leggomieggo10]

pulled tstat, noticed the gasket wasnt in the best of shape, wasnt leaking but maybe air was getting into the system.

either way i cleaned up the housing, made a real nice sealant around it, an left the tstat out. drove in town without overheating, an drove on the interstate without overheating, i hope i dont regret saying this but i think its good to go

thanks to everyone for help

[Alex3000gt]

pulled tstat, noticed the gasket wasnt in the best of shape, wasnt leaking but maybe air was getting into the system.

either way i cleaned up the housing, made a real nice sealant around it, an left the tstat out. drove in town without overheating, an drove on the interstate without overheating, i hope i dont regret saying this but i think its good to go

thanks to everyone for help

Awesome. Sounds like your thermostat was failing partially open. Definitely get a new one in ther soon, but in the mean time... ENJOY!

Always happy to help a 3/Ser.

[Mike-92RT]

hahahh im a genius!!

:)

[Alex3000gt]

hahahh im a genius!!

:)

I solved it, my credit! :p

We can debate this at the NG.

[leggomieggo10]

do you really need a tstat?? ive ran cars without them before

[x2xtreme360]

do you really need a tstat?? ive ran cars without them before

A car can overheat without a Tstat. Of course you need one.

Coolant gets cooled in the radiator until the thermostat allows another stream of coolant inside the radiator. Constant flow in the radiator doesn't have a good cooling effect.

[leggomieggo10]

gotttcha, thanks

[Alex3000gt]

Also your engine takes longer to warm up without a thermostat. This increases engine wear and decreases fuel economy.