Okay, I have beaten my brains out trying to get my '91 305 tpi to stop overheating - I've replaced the sensor that interfaces with the ecm, the thermostat, the fan switch, the sensor that interfaces with the guage (that will happen this weekend, actually), had the radiator rodded out, and the entire damned system flushed. The hoses are fine, and the cap holds pressure. And, yes, the air dam is there, and there is nothing restricting the flow of air that I can find...or the guys at the radiator shop for that matter.

And it still overheats!

Anyone have any ideas as to what I can do next to solve this? I'm thinking aftermarket fans or a bigger radiator or something...I mean, ****, this is getting ridiculous!

 

Nice sig...When does it overheat?? Sitting, driving?? You said you flushed it did you replace anything other then sensors?? You Radiator could be stopped up and be bad enough that flushing it didn't help...Or you could have the water jackets in the engine clogged (doubtful but possible) if all else fails get an aluminum radiator and go with it.

 

Are you sure the gauge is workin right? Or is it obvious that the car is overheating with coolant boiling and all? I would think that on a realatively stock car it would be the radiator just being old or bad if your sure the gauge is workin. But are you sure the fan is coming on when its supposed to?

 

I had a similar problem not long ago. I done all what you did and I also performed a compression check to see if I did not have a blown head gasket. You might have a blown head gasket if you have a compression gauge I would give your cylinders a test.

My problem was that my fan was wired up reverse rotation. So instead of my fan sucking air into the engine bay it was blowing air out of the engine bay. If you stand in front of your car you should not feel air blowing out onto your legs but rather sucking it in. That is another thing worth checking fixed my problem.

If the fan checks out okay then I would do the compression test.

 

I know the guage is reading wrong - I hooked a scan tool up to the computer which was reading 209 when the guage was reading around 250, and I took a laser thermometer to it that read about 5-7 degrees cooler than what the ecm was reading (took the temp at the 'stat housing, the radiator, and both sides of the block). But yesterday on my way home from running some errands the guage was reading 260 and I could hear coolant boiling.
I did a compression test in December and everything was fine - there really aren't any other signs of a blown head gasket (no steam, no oil/coolant mixing, no exhuast gasses bubbling through the radiator); so I don't know about that...

Slow91Z, I had the radiator rodded - where they yank it out and grind all the crap out of it. It kind of does this gradual heating up thing, but it's hard to tell exactly with the guage reading wrong. As best I can tell, it starts to get heated up bad when in traffic or getting stopped at a lot of lights - on the freeway it kind of gradually warms up so the guage reads 250. But I won't know if that's the correct reading until prolly Friday or Saturday.
The fans are spinning the right way, I actually have the primary fan hardwired on. But I'm wondering if maybe the secondary fan isn't coming on...is there an easy way to hardwire that so I can test it? I'm not exactly an electronic genius or anything

Thanks for the help so far guys

 

The second fan doesn't come on till like 250, it has it's own temp switch in the head, totally isolated from the rest of the system...the car is designed to run at 220, and it sounds like you are right on, but that isn't the best temp for it to run at...do you have a stock thermostat?? Sounds like a 170, or 160 thermostat would help you tons.

 

Well it sounds like you have the coolant system taken care of, but how is the tuning?

What is the timing set at? How does the BLM's look on the scanner? If the car is running lean, it will cause the car to overheat. The timing being too advanced will also cause it to run hot. Ever see headers glowing????

I also noticed you haven't replaced the waterpump.... they only cost $26 from autozone, and on a serp setup are very easy to replace.

Does your car have ac? If you gutted it, perhaps the condensor is clogged up? Or you took the condensor out and the air is being channeled through the radiator like it used to be.

I'm also assuming since the radiator has been out, that there is no garbage between the condensor and the radiator

-Snowyz28

 

water pump do that for ****s and giggles its also good practice to replace it

 

1 day when u have nothing to do,go outside and start the car and raise the hood. let it run for awhile and watch the guage too. after it gets to 220,hold the gas at a steady 1,500-2,000 rpms and when the guage starts climing real high,look and see if the 2nd fan is on,if not then thats ur prob.

works better if u have 2 people i reckon

 

the second fan is for a/c only and if your car is getting above 220 thats a problem anyway your drivers side fan should kick on around 225 your passangers side fan only works with a/c are you overheating while driving or ideling????

 

What are you talking about?? the Primary fan comes on when the ECM tells it to (TEMP) the secondary comes on when either the 1. AC is on or 2. The temp switch in the head switches it on, which is like 240 or something stupid.