I also had freaky heater trouble. Cold and warm mostly cold so the dealer did an air bound flush and I had a cracked cap that we replaced and so far so good lots of heat! But my '94 Max was my dads and had only 80k so not too many troubles yet so thanks to all who posted with problems,I'll be better prepared later.

Mike C

 

whats an air bound flush....how did he do it?

 

....Ummmmmm.... yeah: what IS an air bound flush?????

 

Does someone want to address this question?

 

what it means to the dealer is a bleed of the cooling system. air gets in the hoses water pump or rad even if there is a small leak or in my case a cracked seal in the radiator cap. as long as there is no air circulating thru out the engine block the coolant can maintain the temp.

 

I believe you are mistaken. Air won't circulate in an engine. It will rise to the highest point... usually the top of the radiator, the upper hose, and top of the engine. It is possible that smal pockets could get trapped in other places. When it makes it to the top of the radiator it gets forced out through the radiator cap and throught the overflow by the expanding coolant. If there is coolant in the overflow tank, coolant gets drawn back in in its place.

In your case, a bad radiator cap would let expanding coolant or air out but draw air back in... that would be a problem. Replacing the cap, refilling with coolant, and opening the bleeder screw on the outlet would the right thing to do, but it isn't anything unusual.

An "air bound flush" is a term we haven't heard before, and we still don't know what it is or what was done by the dealer.

 

JC... if you have already, I apologize ahead of time, but either way would you care to comment on why some of us are experiencing reduced flow through the heater core causing poor heater performance. I have checked everything except the water pump. All is well except for this lack of flow that gets better with higher engine revs. If trapped air eventually works its way out of the engine, which I believe it does, this issue comes off the table, leaving some other reason for poor heat. But what is it. I have verified flow through the heater core with a garden hose and all is well. This leaves the water pump or something else.

Martin 90SE 5sp

 

Sh*t if I know. I'm in the same boat you are, Brother. I've done what you have. Garden hose flowed fine when I back-flushed the core; water valve works. I won't say that air couldn't get trapped in the core... dunno. Hoses are ok, no major bends/kinks, thermostat replaced, temp guage dead center. Heck, if it is air, the only thing I can think of is to pull a vacuum on the system and rig up something to let it suck in the coolant.

That's why I want a better explanation of what was done.

 

Martin,

Any chance you could find out from the dealer that serviced your cooling system how and what they did for the air bound flush?

Today i left the bleeder screw on top of the engine slightly open while i drove around town just to make sure ALL air escaped through it...Thankfully the heating DID go up, but not too much. i felt a difference for sure.

Tomorrow i will change the coolant (its a bit old) and bleed the system once again.

 

I think you mean Mike C.

 

Ooops!...yeah my bad
Mike C, if u would please...