Cooling system problems

I have probably read through every thread ever written about 308 cooling system issues and I know for certain that there was at least one about an inaccurate gauge. From what you have described it sounds like this may be a very real possibility in your case.

 

+1

 

Yep...the symptom can be caused by low coolant...caused by air in the system. I had EXACTLY the same symptoms. Not saying it's the only possibility but it's certainly first on the "usual suspects" list.

 

I'd expect the coolant to start boiling over around 240-250; is this happening?

I think either the gauge or the sensor is suspect.

 

FWIW, when my 328 did this I discovered it was low on coolant - EVEN THOUGH when cold the level in the expansion tank looked OK. The gauge, in bumper to bumper traffic was going well up toward max , Later I discovered that he same thing would occur if I let it idle in the driveway long enough. BUT there was no sign of actual engine overheating - no odor of antifreeze or the general odor of a hot engine. However, an IR gun pointed at the housing where the sensor is located showed that it was very hot. Interestingly, the fans did not activate when the needle went past the point at which they normally activated (just past the center indices on the gauge). They would still turn on but only when the gauge was close to the last indices. IOW, the gauge/sensor/IR gun said the engine was hot but the fans/engine did not so indicate.

The overheating indication first occurred in bumper to bumper traffic on a trip from MD to TX last year when traffic was stopped on I-10 in Houston due to an accident outside temps were in the low 90's. Until this happened, my 328 had never done this in the 9 years I had owned it, including sitting in stopped traffic in 108F outside temps with the AC running. I pulled off the highway onto a side road, expecting to have to park the car/make some sort of arrangements for repair, but the temps dropped to normal almost immediately when the RPM went above 2k or so. So I drove on to San Antonio.

After arriving in SA I started doing some research here and found numerous articles explaining that if there is air in the system, coolant can be expelled from the expansion tank even though the coolant level is OK and the engine temp is OK. My car had routinely been spitting coolant from the overflow since the coolant had been changed by a shop in MD almost two years earlier . I had INCORRECTLY assumed that they knew what they were doing and that the coolant spitting simply indicated that the system was overfilled. YES, you can legitimately ask why after doing this for two years why didn't I do some more checking. Well, I did check the level in the expansion tank and it was OK so I just assumed it had been grossly overfilled!

As it turned out, it was not. I did a thorough bleed and that's when I discovered that it was low on coolant - again, even though when cold, the coolant level in the expansion tank was OK. It had been spitting coolant regularly due to incorrect initial bleeding which, ultimately, resulted in insufficient coolant circulating under low speed conditions. There is an article on the site that suggests that air in the system can cause high temperature gauge indications because the location of the temp sensor allows the sensor to be "out of the water" if engine (and water pump) speed is very low. When the engine/pump speed is faster, the higher flow of coolant then puts the sensor back "under water." I can't guarantee that this is exactly what happens but I can say that the explanation DOES exactly fit what was happening. IOW, initial bleeding when the coolant was changed did NOT expel all the air and that air caused the regular spitting which, in turn then caused MORE air to enter the system. Obviously, at some point it could, I assume, expel enough coolant that the engine really would overheat as opposed to just the gauge indicating that.

After the thorough bleed/top-up - 3 times - last year, it has yet to spit any coolant and it is back to its normal state of the temp gauge never rising more than a needle-width above the center indices on the gauge, regardless of traffic/outside temp.

Again, not saying this is the problem you are having, just that it COULD be. Good luck and hoping for an easy and inexpensive solution!

 

If the IR gun says 190 but the gauge says 240 and you are concerned which is correct why don't you check it out by spraying water in the area where the gauge sender is located where you say you are measuring the 190 F temperature. Note whether it immediately vaporizes. The engine is aluminum so if the coolant temperature is near 240 F, the surface external temperature of the aluminum will be well over 212 because the only cooling it sees is natural convection and radiation. Aluminum is an excellent conductor of heat so the external surface temperature is close to the coolant temperature. Or you could dip your finger in water and touch the metal where you are measuring with the IR thermometer. If it does not sizzle, temperature is below 212 so your gauge is registering incorrectly for some reason. Even if the temperature is over 212 F you won't burn your finger because your finger is wet and the energy needed to vaporize the water on your finger is great so it is diverted until the liquid on your finger evaporates.

 

I forgot to mention in my post, above, that I found that after the bleeding of all air, I had to add well over a gallon of coolant to bring it to the proper level - actually, I think it was close to two gallons but I don't remember now. So this is how much coolant had been spit out over two years due to improper (or no?) bleeding after the shop changed the coolant. Again, most of the "blame" is mine for not really looking into why the car would spit coolant on a regular basis. Common sense, which I clearly did not apply, would dictate that although a bit of spitting after a coolant change is normal if the system is a bit overfilled, it wouldn't keep spitting/stay overfilled for two years!

Yes, there are other causes for spitting coolant/air in the system- blown head gaskets, crack in head/block, whatever. But if caused by blown gasket, etc, the symptoms don't disappear when proper bleeding is done.

 

FWIW, I tried this on the thermostat bleed location in my 308 QV - seemed to work OK for a year or so, but... just last month I was overhauling the fuel injection system (fuel distributor cleaned and flow balanced, original steel injectors cleaned, cold start injector cleaned, broken warm up regulator rebuilt, plastic sections of the injector lines replaced), and on the test drive after I got it all back together, all of a sudden I noticed steam coming through the right side of the engine lid, Luckily I was only 2 minutes from home, so I returned home to check. As I parked the car I could see a trail of dripping coolant had followed me up the street...

The top piece of that automatic bleeder valve had separated from the unit, leaving a tiny hole for coolant to spray out. I was very lucky that I was so close to home when it happened, but if I'd been further afield, that failure would have required a roadside stop and a tow (and fingers crossed that I would have noticed it, at highway speeds it wouldn't have been easily spotted until the temp gauge would have gone nuts).

I removed the automatic bleeder valve and put back in my old Unobtainium drilled bleed screw, and have resolved to stop trying parts that aren't intended for automotive use. The auto bleeder valve worked for as long as it held together, but it was designed for home radiator use, and not designed nor intended for automotive use where higher temperatures and vibration characteristics create a tougher duty cycle.

Just a cautionary note,
Gordon

 

Well that’s pretty informative. There have been no long term tests of these little devices. The one on my radiator is still functioning after 4-5 years and should probably be replaced. I suppose yours might of had a defect who knows? In any case I do carry a spare in case of a catastrophic failure like you suffered.
Thanks for posting your experience.

 

I installed one of those at the T-stat housing when I went through the bleeding procedure last year that I described above. BUT I readily admit that the concept bothered me for exactly the reason stated - it's valve designed for use in a home - with less heat and no vibration. Ever since I put it in, I have been thinking of removing it and putting the OEM fitting back in - or maybe I should buy the quick-bleed fitting. Don't understand why the 328, which has an OEM quick bleed at the radiator, does not have one at the T-stat.

 

I’ve only found that the one on the radiator was needed. Also less heat and vibration.
Results may vary!

 

That might have been the difference - the radiator location will not have nearly the vibration or additional heat that the thermostat location receives! I was running a Ferraripilot radiator, which had a different size threaded hole for the bleed location and couldn't use the automatic bleeder valve.

 

I bought the auto-bleeders and found they don't work. They use a hydroscopic seal that closes when it gets wet. Well, when you bleed all the air until coolant is flowing out and then install the auto-bleeder it is then "wet" and sealed and I've never seen them dry out in use to the point that they would bleed any more air even though there was a large amount of air at the top of the radiator. Maybe if you let it sit for a week, I don't know. I took them out and put the drilled bleed screws back in so if anyone wants them....

As for low coolant I can attest that after completely draining my system, including the block drain and replacing all hoses I was only able to get a little over three gallons back in before coolant was flowing out of both the radiator and thermostat bleed ports. It took a number of drives and subsequent bleedings at the radiator before I was able to get the amount of coolant back in that I had drained out which is 18 liters or just under 5 gallons. So my suggestion, if you are renewing your coolant, is to drain it into a five gallon bucket and measure how much you took out then make sure you put at least that much back in. Otherwise you're not done yet.

 

LOL...due to this discussion re the home heating valve, I went to the hardware store, bought two bolts the same size as the OEM bolt for the T-stat housing. I took them out to the garage and converted them to "quick-bleed" fittings using the drill press/drill press vice. Don't know why I didn't do that last year.