engine and drivetrain Thermostat question

[dtharp113]

Further underscoring the saying -- if it ain't broke, don't fix it...I replaced the 2 heater lines that run into/out of my choke yesterday (because they were leaking coolant and the rubber was crumbling around the hose clamps) and now my heater blows cold and (I'm surmising) the engine temp runs hot. Prior, my heater would warm up quickly and very nicely.

The radiator hoses on the top are hot, but I'm guessing only because they're next to the block, and the radiator is cool to the touch.

I checked to make sure the hoses were located properly, and the coolant level is good.

I've pulled the thermostat but is it even worth testing? Is there anything else I should be looking at?

She's a '75 w/ a Weber 32/76 DCAV3 carb

Thanks

Dennis

[Das02]

Most likely air is trapped in the heater core, or the t-stat is stuck open.

What I'm interested in, and this is a little off topic, is why with 2002's, the lower radiator hose never gets warm? My car does not overheat, nor does it run too cool. Even after a long drive, the lower part of the radiator and the lower hose are always cool to the touch. On other cars once the t-stat opens up, the lower rad hose warms up.

Anybody care to explain??

[Guest Anonymous]

Your post reminds me of Goldilocks and the three thermostats! My lower radiator hose is cooler than the other hoses, but still hot to the touch. I currently use a stock recently recored brass radiator with a 75 degree therm and rarely have the gauge above 3:00 o'clock.

I have tested all of my thermostats, even the new ones, to make sure they actually operate and do so fairly consistently. I have, gulp, drilled small bleed hole/s in some of them to avoid the trapped air controversy and as a little bit of insurance. I have found that the small hole can produce slower variations in temperature, although this is not empirically proven.

I also do not know about the air in the system controversy, since I have never experienced it - with or without a thermostat bleed hole and do not recall any of the reference materials discussing bleeding the M10 system. Yes, I am aware that the M30 engine actually has a bleed screw in the top of the thermostat housing cover.

Sorry I can't answer your question directly, versus indirectly. :?

[dtharp113]

Well, it's looking like the t-stat is working properly (least it's opening and closing).

Oh, did I also mention that w/ the new hoses to the choke, I'm now idling +1K rpms prior to the change?!? When she starts up, she'll idle at 1500 -1800 rpms (which at that rate, idling doesn't seem like the correct word).

D

[ingraham]

The fast idle suggests either 1) the engine is not warming up or 2) you changed the choke adjustment while replacing the choke hoses.

Maybe some schmutz in the cooling system got knocked loose during the work and lodged somewhere else, such as the heater core. You could try reverse flushing the heater core with a garden hose.

I've never had trouble bleeding a freshly filled cooling system and never needed to use any tricks to do it, so I can't explain why 'trapped air' happens. Sometimes it takes one or two hot/cold cycles with minor top-ups when cold before the coolant level stabilizes.

You were correct in replacing the old choke hoses. Now is a good time to check all the other coolant hoses.

[satsuma]

I squeeze the lower and upper rad hoses a few times after filling the coolant, acting like a crude pump it dislodges some of the trapped air.

Ben

[dtharp113]

Well it seems that the situation is under control. I ended up taking her for a quick spin and within a few blocks, hot air was blasting out! Guess she just needed to be burped.

I agree w/ you about replacing the other coolant hoses -- that's next on the list before Jan.