Another air in the cooling system question

The new water cooled P cars have air bleeds at the top of the radiator that run all the way back to the expansion tank. I've also seen the same schematic recommendations in some race car engineering books.

Air in the system maybe "normal", but if my car is topped off it will take 20-30 minutes of WOT to get the water up to 220 f. Minimal air I get about 10 minutes fo WOT. A lot of air I run at 200 f and get to 220 f pretty quick at WOT. Air is not good if you're loading the heck out of the cooling system but if you're just driving around town "like a minivan" I agree who cares if it's not overheating.

cheers

edit: I think an important aspect to consider is any air that is being created for whatever reason is supposed to end up in the radiator IF there is no top bleed back to the expansion tank which is where it really belongs from a design point of view. If the air didn't accumulate in the radiator it would build up in the engine which is worse. Some Porsche guys told me that not only should the bleed from the radiator be run back to the expansion tank, but also the bleed from the thermostat housing should be connected to it. This makes sense to me from an engineering point. Ignoring the fact that Ferrari didn't do it, does the fact that Porsche does it or does just pure physics make any of this hold water ?

 

Could the factory water pump be creating air?

Do other cars being discussed here (including Chevy's) actually have a scroll impeller vs. the stock "paddle" that is in the 308's?

I don't see how the stock pump would not create air but if that's how all automotive pumps are I guess that wouldn't be a culprit unless the clearance is not correct which I recall one of the old timers mentioning here.

It was also mentioned the F40 uses the same pump ... does that have bleeds on the radiators hooked up to wherever the expansion tank is? It's all in the details .

cheers

 

I had a 996 911 for 7 years - I tracked it and drove the heck out of it. I changed the coolant every 2 years and there was no drama at all as far as draining/filling/bleeding. I never had to do a thing with the system between the drain periods. I had friends with the same cars that never changed coolant at all during the same time frame - no issues with air. Should be the same for 3x8s. As stated, cooling systems are self-bleeding at the pressure cap. Once the system is properly filled, that should be it until you decide to change the coolant or sell the car!

 

The old water cooled P cars have a bleed that goes from the top of the radiator back to the reservoir. My 1986 944turbo has one. It also, of course, has a block bleed. Ferrari should have installed one on the 3 series but it would be a long line. It's only about 15 inches long on the Porsche.

The top of the radiator is a good collection point for any air that gets into the system. As I said, I think mine gets there from the churning of the water in the reservoir and eventually gets trapped in the top of the radiator. The air collection is and always has been a small amount but, nevertheless, presents itself. I am quite sure there is nothing amiss in my car. Like I said, it has collected there for 22 years with never a cooling problem. A leaking head gasket would have gotten much work by now and would cause coolent to be expelled by the cap relieving excess pressure. I only add coolant when I change it every other year.

 

What's your point? The cooling system on the P cars is way more sophisticated ... did you catch what I posted about the bleeds on the radiators being connected back to the primary expansion tank? There would be no air in the 3x8 radiators if Ferrari would've done this I'm thinking?


cheers

 

Yes, I saw your comment re the air bleeds on the Porsche. My point is that 996s with remote radiators had no problems and 3x8s had no problems at the same age. My 328 has been just as easy to deal with coolant-change wise as my 911. So clearly there is NOTHING wrong with the original design of the cooling system that causes air to be ingested. If the system was properly filled in the first place and air has to be continually bled from it, "something," as they say in the aerospace industry, "musta' broke.".

 

So why did blocking off the small upper line to the expansion tank on my car solve the problem? I agree something may not be right and they probably didn't do this as bad when new. I do however think there is something of a design flaw with the system, at least on the older cars with the veritcal tanks. Without an internal pipe to keep that upper connection in the coolant how can it not draw air back into the system when the car shuts down.

So, once again if anyone can explain how blocking the upper line cured the problem and can point me to the real problem I'm more than willing to listen and learn.

 

That's funny I thought it was the horizontal style tanks that were more prone to the problem ... and my theory was due to the ease of uncovering of the lower line in the horizontal configuration. There are no tubes or baffles to speak of in any of the horizontal tanks I've seen either. Are you a pretty aggressive driver where you think you might be uncovering the bottom line on the tank? Was it a check valve or a plug? Is the thought that the water/air is sucking backwards thru the small line during some condition?

I tried plugging the top line and I still got air in the radiator. It was just recently I had air in there again even with the secondary catch tank which is why I mentioned perhaps the water pump might be a source of the air. My car wasn't running hot ... I just decided to open the bleed screw and there was quite a bit of air in there. Now she runs cool even on these hot days .... so cool I'm back to thinking about air conditioning .

cheers

 

I chased a similar air problem for longer than I care to admit. Re-cored the radiator, replaced all hoses and clamps from under the plenum back to the radiator. Still ended up with air. "Fastradio" advised me to first pressure test the system cold and check every connection for leaks. Well, purchased a tester and Bingo, I had multiple connection failures. I guess I read to many horror stories about crushing the tubes and I failed to tighten some of the SS clamps properly. Thermal expansion was allowing air into the closed system as it cooled. If you got air, you got a leak! Thank You! "Fastradio"

 

Bad thermister, gauge or ground.

I'm guessing a bad ground!