I have been dealing with an overheating issue for a while and need some help. My 91 camaro runs hot when at idle WITH the fan running. it will over heat in the texas summers. It cools enough (but still 230) at highway speeds but climbs when in slower traffic and at idle.

I have replaced the radiator (1" single core), pump, thermostat 180 and fan motors. The system has been back flushed with nothing coming out there and flow seemed to be ok.

The car has edlebrock intake, bigger throttle body and a new chip. No headers.

Thought it may have been an issue with the fuel tables in an aftermarket chip that was in there but just tonight we put in a better tuned chip (from lou) and even though there is a few things that need to be tweaked (it does run better) it still runs hot. About 230-240 tonight at idle in 70 something deg weather. 220 while driving around for about 30 minutes. There was an issue with the first chip not registering with the laptop. So there is a new ecm (remanufactured) and the new chip.

There is a stock fan right now that runs constant and doesnt really seem to be doing any real cooling just maintaining. After about 30 mintues of driving and data loggin the car still runs about 6-7% lean at idle, not sure that minimal amount would cause the hot condition.

No codes either now with the new chip...Just a new shift light that got under lou's skin..lol

There is one injector that ticks on the passenger side so there may be something there but not sure if that would cause a condition worse enough to overheat. not sure what lbs injectors are on there.

Pulled 3 plugs on the drivers side only and there really didnt seem to be any issue with them, light brown mostly. Lou and I compared them to some images he had to be sure and they seemed to be ok.

Timing is advanced 8 deg.
Any ideas?

 

If you're absolutely positive the coolant is circulating correctly (?) then it pretty much has to be the lean running. So first you probably need to find out exactly what injectors you've got and if they function correctly. No good fiddling with the chip if the injectors are bad. At least test resistance and maybe get them cleaned/rebuilt flow checked etc. Then the other stuff.

 

It may sound stupid but have you checked under the car to make sure your air dam is still on your car? You may also check your timing not sure if being to fast would cause it to overheat or not.

 

yes the air dam is fine.

When the system was flushed the water flow out was about the same as the hose flow going in, so it definitely didnt raise any eyebrows while we were doing it. I replaced the pump and I guess I could have got a bad one but it would have to have been the same issue as the one I replaced as the symptoms stayed constant after the swap. So I dont think it is a flow issue. When I take the rad cap off I can see the coolant swirling, about the only I forgot to check was to see if the lower hose compresses or not. I did look at one point and didnt notice anything there but I dont remember if I did it while revving or not. So I will have to double check that one again.

I say I do not know for sure on the injectors but I believe they are the stock ones. That being said short of buying a larger rad and more cfm fans (which will mask my problem and not the real issue), I wonder if it could be a combo of the advanced timing, (possible) injector issue, which I wont know until this weekend when I can get an ohm meter on it, and it running lean. I dont necessarily think that each one isolated would cause an issue but it may be a combo affect. I am not really sure at this point.

When we data logged the car the fuel tables were still off in that it would run lean at acceleration and rich on constant throttle. So there is some minor tweaking that needs to be done there. Like I said before it will run lean at idle but only after we took it out for run, it didnt run lean when we first started the car and let it get up to temp.

 

If you dont know what injectors you have.. how did they know what to set the injector size at on the tune?!?!?!? id say your running very lean and its causeing the problem...becareful not to burn it up...

 

have you checked the radiator cap?? i didnt see it in your list of things. pull it off and take it to autozone or oriely and have them pressure check it for ya. its one of the most commonly over looked things and can cause problems like this. and just because its bad doesnt mean your gunna see puddles of coolant on the ground.... its probably just not able to hold pressure any more.


hope this helps

 

they are the 22lb stock ones. wasnt an issue for tuning the car. although the oxygen sensor is on the left side so the right bank readings could be running leaner.

 

no i havent checked the cap yet. and that is a good point. Probably just as easy to pick one up on my way home and put it on there and check it out.

 

Have you tried putting a stock chip back in or resetting the current to default settings? It may help eliminate some of the possibilities.

 

well there really isnt a stock chip since the car has a 350 with a 5 speed attached to it. So either way the chip will have the wrong settings for the stock 350 auto or the 305 manual. I pretty much have to go with a custom chip, which isnt an issue just need to finish out the tune now that we have data logged it.

 

measured the injectors today and all 8 ran 16 across the board. Fuel pressure is fine too.

Checked the temp behind the fan at idle and it was hot and when revving the engine the heat behind the fan significantly changed to VERY hot.

There are some weird things in the data log that was found like the BLM would change before the MAP and not along with it. Not sure why that function would change on its own before more input from the MAP was received but that is what we noticed.

 

Have you changed the fan switch most people change to a aftermarkt one I got one that comes on at 200 degrees off at 160 sems to be working pretty well stock usally comes on at anywhere between 230 to 238

 

if it hasn't been said already... "check your timing" ....

 

well there is one fan set on all the time.

Timing is advanced 8 deg.

Checked for any underdriven pulleys=no

still same situation.

 

Pulleys would imply that you've gotten away from the single serp belt? This would require a different water pump from the stock replacement for that year.

Rad cap is around $3. They wear out over time and need to be routinely replaced anyway.

 

What way is the air blowing? You want the air blowing towards the motor.

Radiator ------> Motor

 

Are you sure it is running hot and not just a bad temp sensor ?
Yes the lean condition can cause it to run warm, but shouldn't affect it much at idle. You may try and setting the timing back to 0 and see if that works. Maybe getting to much advance if the timing curve in the chip modified.

 

I am having a similar issue with my 305. I'm not sure what the readouts are on the injectors, I did the hearing test on it, a couple have heavy clicking sounds (2,4). I redid all the hoses, cap, thermostat 190, temp sending unit, and new pump(actually did this twice, the first was defective). Let me know if readjusting the timing works. I can't do it right now because it's around 4 degrees outside and my garage has my other camaro I'm working on. Also, does your service light come on when it's warmed up, mine does.

 

air is blowing fine, and as far as the serp belt set up I was simply looking for wrong sized pulleys just as a check. Temp sensor is fine, that has been tested with an infrared and matched the car and the laptop.

I was getting a service light before but that was with a bad chip. Since then a new chip has been made and no light comes on. Increased the fuel on a new NEW chip to work out the lean condition but just havent tested that yet. Although i do not think it is the problem anymore.

 

I had a similar problem on my carb'd 350. It was a new crate motor and was going to 230 and even 250 ! I changed the radiator and still didn't fix it...I yanked the thermostat and thought it was fixed a for a while. Finally I noticed that under acceleration my lower rad. hose was compressing on itself. Also , the thermostat was set for 185 or maybe 190.

 

what direction is your waterpump rotatating in? (serp belt?)

 

Key issues, from above.
-- pump rotation direction. Serp. driven pumps are opposite
of v-belt driven pumps. Was there ever a switch-over?
-- rad cap. Easy enough to check: either at a parts house or
when the temp is 200+, look for steam or boilover into overflow tank
-- lower rad hose collapse as engine rpm increases.

Another little known, but critical issue.
For some reason, these vehicles can recirculate heated air from behind
the rad, back to the front of the rad, through a gap between the rad
and core support. The factory's brilliant solution was to stuff a piece of
foam in the gap, which is easily lost whenever the rad is removed.

Good luck

 

What is your timing at idle?

Also, at what point did the overheating start? Was it right after the new intake manifold install?

 

i work at an Auto Value and my books are calling for a 16 pound cap. not trin to be a smart *** just sharing some info

 

I believe KOS 22lb reference is referring to the injectors... 22lb for 5.7 and 19 for 5.0 ... the 16 lb is the radiator cap....