308 Cooling system question/problem

My 1982 308 GTSi is trying its level best to overheat. While the belts have been done at 5 years intervals the water pump has never been changed. First question: is the water pump changed due to a leakage (seal) problem or because it loses effective flow? The radiator was removed and recored approximately one year ago by Competizione. I have changed the thermostat. The car beginning to heat up to approximately 180-190 degrees then dropes to approximately 140 degrees (thermostat opening), again heats up to 180-190 and repeas the process, then heats up to an over temp condition. The car is not loses any water or puching water out. I am considering a Nick's water pump but wish some suggests before spending the money. Radiator has been bled. Thanks in advance Steve Schroeder.

 

Just for clarification : have you confirmed fans are cutting in ?

 

I should have addressed that issue. The answer is yes, the fans are working.

 

I had a similar problem with overheating noted on the gauge. After replacing parts and still finding high temperature readings my independent mechanic verified via temp gun that the temperature was normal even though the gauge was showing high temps. I removed the gauge and cleaned the contact points which solved the problem.

 

Your car reaching temperatureres of 180-190 degres is not exactly overheating, happens to be normal operating levels. If you are droping down to 140, probably as a result of the fans kicking in, you are one of the lucky few to have you coolant running at that temp. Sounds like your guage might be in accurate.

 

+1 190 is normal op temp

 

But isn't he saying "...then heats up to an over temp condition" -- i.e., greater than 190 deg F? If it indicates a very high temp at the gauge, but doesn't expel coolant (or at least crackle/moan/groan a bit), I'd tend to distrust the sensor/gauge first.

 

That sort of temp fluctuation, if it is actually happening is not normal or correct for any engine. I have never heard of a water pump causing such behavior.

You said it is not losing coolant. Are you basing that on actually checking the coolant level or just on the fact that none appears to be escaping anywhere?

When did this start happening? If it started after work was done on the radiator or since you changed the thermostat, it's not much of a stretch to assume that the work done caused the problem in some way.

 

180-190 is normal, but maybe the thermostat is sticking a little, causing the fluctuations. Try replacing the thermostat again. I assume that there are no air pockets in the system and it is full. Was there a small air bleed hole in the thermostat?

 

I was told by the PO of my car that he used to open the radiator cap after driving every time to let out air pockets which develop (obviously after the car cools). Do any of you do this? Is it a common practice to occassionally do?

Jim

 

Doesn't sound like a bad water pump impeller. If it was, the problem would be there all the time, it would not fluctuate. Before you go too crazy, pick up one of those infra-red thermometers and check the temps at various points in the system, at the different stages that you are experiencing. That will tell you for sure whether the problem is in the system or the gauge. Never hurts to clean the contacts on both the sensor and the gauge, as suggested. And the thermostat change is an easy one and cheap. Might be worth doing just as a test of the system.

 

I am beginning to doubt the water pump. Sounds more like an air bubble in the system. The water level is approximately 1" below the cap at the expension tank and there in stays. I have seen the temp gauge go from 190 to 140 degrees instantly.

 

Same with my car. Per mechanic's test, gauge reads about 10F higher than actual temp.

I've intended to do as you have and clean contacts, just haven't gotten around to it...will do so now that I've heard of some positive results.

 

I agree.

 

Shouldn't need to do that. Once filled correctly it should need no more attention of anykind until it is in need of changing.


I remove my radiator cap once every two years.

 

What do you mean by "instantly"? In the blink of an eye or over a few seconds? Blink of an eye would have to be an electrical problem. Over a few seconds or more should indicate a temperature problem.

 

In the blink of an eye!!!!

 

I had the same problem. The solution was to bleed the system on the radiator and on the thermostat, twice, three times, four times... And after that the temp was fine: 190 in city traffic, less than 160 on clear road.
Start the car, let the temp to rise and after bleed it in both points. The day after -or a few hours later, after drive it-, do the same operation. The day after the day after, same procedure... Stop finally when you open the bleeding screw and no more air comes out. The system is too long and is easy that some air bubbles remain trapped on the tubing -the engine is a the rear and the radiator in front-.
My 2 cents.

Regards

 

OK, my guess is that the temp guage/sender wouldn't be able to respond that quickly to even a very sudden actual temp change. But I admit it is a guess. I'd want to prove it by removing the cool temp sender, clipping a ground wire to the body, turning the car on and dropping the end of it in very recently boiling water. How quickly does the needle rise on the gauge? I think that the mass of the temp sender will cause a rapid rise over a second or two, but not "blink of an eye" quick. And in the engine it is installed into a larger heat sink (the Y pipe), so its response would be even slower to an actual flood of hot water.

Try it and let us know. I think you have an electrical problem by your description.

On my car the Y-pipe floats in the engine valley supported only by rubber hoses from the heads and water pump and has a ground wire for the sensors in it. At some point 308 engines got a cast Y-pipe that bolts to the heads. I don't know if this bolt-on pipe needs or has an additional ground wire. Whichever one you have, I'd make sure that the Y-pipe has a good ground and isn't corroded and floating occationally at not-quite-ground.

 

Have you checked to see you have an oil cooler present? As I recall there's also a fan on the oil cooler (on my 308 there is at least)....perhaps check if the fan is operating properly. More than one 308 owner has found out (to their surprise) that a prior owner has removed the oil cooler....

 

They did not come with a fan on the cooler.

 

Do you really think they did that at the factory?

 

During the radiator removal process is it possible to have spread the terminals that slide onto the fan switch? Which may cause the fans to work intermitantly. I found a 140 degree fan cycle switch that I installed in our car. The fans run a bit more but that is not a problem. Also I would suspect the ground with either the motor, or the gauges. The only way for a guage to fluctuate that fast is to either loose the ground or the hot wire continuity. I have an infra red hand held thermometer and the following temps were observed on my 308 today with the ambient temp in Seattle 90 degrees. We are having a damn heat wave.

Radiator core on the coolant return side at full operating temps, radiator inlet 190 degrees, on the outlet side 180 degrees(facing the front of the car). In the engine bay main water outlet from motor forward to radiator 190 degrees right out of the motor. Main return line from radiator just before entering the motor 180 degrees, heater hose leaving motor 190 degrees. Interesting enough there was very little difference of temps between the aluminum tubing and the new silicone hoses I just installed.

We have totally remanufactured the motor,fresh and tight new pistons, rings, valves, guides, bearings cams ground, and I did add a forza water pump. This pump has a considerably closer clearance between the block and the impeller than the factory unit which leads to much less cavitation. Cavitation is the reason for poor water circulation. I only have about 2 hours of run time so far so I am expecting some lowering of the operating temps when I get more drive time. My temp gauge runs at a steady 195 degrees and I expect that it is reasonably accurate.

As a side note the further you hold an infra red thermometer from your heat sorce the less accurate the reading will be. While each manufacturer has different specs on the optimum distance for for accurate readings I have found that around 18 inches seem to work with my Snap On unit.

Howard Musolf
1981 308gtsi.

 

Ah, interesting. Mine has a SPAL fan on it with what looks to be a factory loom on it. Works very well - have had my car in some serious southern calif heat and she never gets hot.

 

The fans come on correctly. I'll try to bleed the system again but I think perhaps poor circulation.