A slightly different thermostat question

[Mike McKown]

are you sure your water pump is circulating the water? Drop in a new thermostat. I know some will argue with me but I have no problem with say a 89 323 thermostat and they are dirt cheap....not even 10 bucks. Get the higher temp one....195 I think ...if they have it. See if that helps...if not....you may have a circulation problem. Or...the heater core could be clogged around the outside with a mouse nest or something...not letting the heat actually dissipate as the fluid runs through.

I just put a new water pump on it as the old one was leaking. It didn't make any difference. I realize changine the pump doesn't guarantee circulation.

See the suggestion above on the bypass tube blockage. There might be a problem there. Don't see how really but it's worth checking.

[m715]

Actually, I always wondered if that bypass system was keeping the flow from being controlled by the thermostat, and the heater hoses were bypassed in the system as a result of blockage in the head or the block.

[m715]

Maybe this will help(or confuse)the diagnosis... Sorry about the lighting, but I had turned out the lights in the shop getting ready to leave for the night.

HTH
Michael

[25Horseplay]

Mike I just went though this very same thing. It ended up being a heater core, the best place I found to buy one was online at rockauto.com. It isn't as bad of a job as I thought, it took approx 4 1/2 hours. You have to remove the dashboard from the car and its right there!

[Mike McKown]

Maybe this will help(or confuse)the diagnosis... Sorry about the lighting, but I had turned out the lights in the shop getting ready to leave for the night.

HTH
Michael

Yeah, the flow diagram shows the coolant will circulate through the heater, even if the thermostat stays closed. Thanks.

[Mike McKown]

Mike I just went though this very same thing. It ended up being a heater core, the best place I found to buy one was online at rockauto.com. It isn't as bad of a job as I thought, it took approx 4 1/2 hours. You have to remove the dashboard from the car and its right there!

Can I assume your core was not plugged but maybe had tubes coated with ??????? and prevented the core from transferring the heat?

[ejp2fast]

Rockauto has the stats for like $20.

Just to note to readers about t-stats.... McParts stores and Rockauto only have single stage, and OEM Ford and Mazda have dual stage... this is one instance where OEM is much better... See sticky at the top of this section on "barely any heat".

[ejp2fast]

Maybe this will help(or confuse)the diagnosis... Sorry about the lighting, but I had turned out the lights in the shop getting ready to leave for the night.

HTH
Michael

Thanks for that diagram! Saving to my archive!

[TominMO]

he has mentioned he flushed the core with the hoses off at the beginning of the post.

Right, but he didn't use radiator flush, just water. Makes a big difference, as I have recently learned.

[Mike McKown]

Right, but he didn't use radiator flush, just water. Makes a big difference, as I have recently learned.

You're right, I didn't use a commercial flush. The heater rinsed out clean with clear water, no rust, no scale. The inside of the block in the water pump opening was the same way. Clean.

So, when I verify the heater bypass tubes are clean, flushing the heater core with a chemical will be next.

I really don't know what else to check.

[m715]

Sounds stupid, but you might try a clear tube from the intake to the heater core to varify you have flow into the core. Just a thought.

Good Luck!

Michael

[Mike McKown]

Sounds stupid, but you might try a clear tube from the intake to the heater core to varify you have flow into the core. Just a thought.

Good Luck!

Michael

Not a bit stupid, I didn't mention it but that's exactly what I had in mind. I bought the clear vinyl tubing yesterday just for that purpose.

You have a good head.

[hot4dl8ly]

You might also try flushing out the heater core by itself with something that disolves calcium/lime buildup. Take heater hoses off intake and tube that leads to water pump, point hoses up, get as much coolant as possible out of core, let cleaner soak for awhile and flush through with strong stream of water. I have marginal heat and go through this every year or two- seems to help- (ought to bite the bullet and change out the core). I had car running very hot on hwy soon after I got it- turned out to be partially clogged radiator. Wanted to get it rodded out and radiator shop said whatever was in tubes was "like concrete"- I figured the heater core probably got same treatment. Good luck with it.

[Mike McKown]

Okay, while ago I put a clear tube on the heater return line that runs from the heater core and the steel tube by the distributor. I also installed a clear tube from the thermostat housing to the radiator.

There is plenty of circulation coming out of the heater core. It goes through the clear tube in a gush when you rev the engine.

I let the engine idle for about ten minutes. The engine cooling fan never came on, the engine never really got hot. The top hose to the radiator never flowed any coolant so the thermostat didn't open either.

It looks like the coolant is flowing okay but is bypassing the thermostat altogether. One path is through the heater core, the other through the small hose that connects to the thermostat housing and connects to the large bypass tube.

During the ten minutes the engine ran, none of the hoses got hot, not the radiator hoses or the heater hoses. They just got warm. The fan never came on.

I'd say the hoses are about the same temp as the air coming out of the heater so I don't think I have a crudded up core. I'm starting to think the problem is a thermostat that doesn't open when it's supposed to, the coolant is circulating from the pump, through the heater, through the by-pass pipe and back into the heater without being circulated through the engine to pick up heat.

There's a few flies in that theory but that's the best I can come up with.

Anybody?

[m715]

You are headed down the right path IMO. This is a strange problem that has a tinge of Deja Vu! Now if we had xray vision to see in the block, or the next best thing a hand held pyrometer......