Cooling system stuff...

fiatmonkey

fiatmonkey

Tim Hoover
Hi folks,

This post might be a little premature as I can do more tests, however I am trying to nail down a cooling system gremlin. When at idle, my heater core never heats up however at rev (anything 2k or more) it it discipates heat ok.

I bled the system a few times but did not help. The radiator fans cycle properly (on for about 35-40 seconds each cycle) and no signs of overheating.

Some strangeness:

I noticed the coolant that drained from the bleeder had a LOT of fine bubbles - not quite foam but close. I also confirmed the expansion tank also had bubbles (while the car was running). I have never seen this before? I am pretty confident the head gaskets fine, good compression etc. I have NOT ran a cooling system pressure tests. I plan on doing that in an hour or so after I track one down from a local parts store.

What should I look for when testing the system pressure?
-Tim
 
!!!

My guess would be a collapsed or pinched hose. The water that does get past the restriction would be whipped up (lots of tiny bubbles).

If there's a large hose pinched or collapsed, the water pump will cavitate, which is just whipping air into the water (LOTS of tiny bubbles). The air could be collecting in your heater core.
 
Pressure test reveleaed 2 leaks; one at the water manifold near the thermostat and the other lower front radiator. The front leak didn't show for a little while under pressure but was pretty bad. Car now holds 14 PSI no problem. I actually haven't re-bled yet and the heat dissapation issues (lack of it) seems to have gone away or maybe just gotten better where the heat from the heater at idle (under 1200) is noticeably better. I am happy with it. When the weather gets better (its miserably cold and foggy/overcast today) I will get out and have a look for the bubble issue again.

When I tested my cap it couldn't hold anything past 9PSI before releasing. Its only about 8-12 months old and I am pretty sure it was rated at 13. It could be the tester but assuming its not (since I don't have another one to test with) this is a valid concern?

-Tim
 
I had the same issue once

you'll need to run the car for at least 15-20 min. at operating temp with the fill cap off and the heater on "hot" after re-filling the system. The engine will have air pockets in it that will need to escape. This is in addition to bleeding the radiator. Don't walk away during this process. Keep an eye that the expansion tank doesn't suddenly run dry from a big "burp".

Increasing the system pressure elevates the boiling point of the fluid (and stress on the system). If you're just idling in the driveway, you should be able to run forever without the cap if the fans and thermostat are operating properly.
 
Are you guys taking the plug out of the t-stat housing when filling the system? I loosen the bleeder on top of the radiator, remove the t-stat plug and fill the system till coolant runs out of the t-stat housing. After putting the plug back in I go up to the front of the car and make sure coolant is running out up there (it always is). After closing the bleeder and making sure the tank is topped up I put the cap on and drive the car. Never had any issues with this procedure even on a completely dry cooling system. I don't know if all cars have the t-stat plug. I imagine it would be a pain without it.
 
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