still overheating! YES!

ThunderChicken · Mar 18, 2007

so...the water pump and gasket have been replaced, and the thermostat as well.

car still runs IN the red, and after turning it off, the radiator is cold, and it blows cold air.

correct me if i'm wrong, but this sounds like a malfunctioning/clogged heater core to me. what do you do to fix that, some kind of Drano-esque flush, perhaps? or will i have to replace it?

the water pump i pulled out had six large aluminum blades, and the one i put in looks like this...

has anyone noticed any significant difference like this? i.e. could the new pump be pushing less fluid due to its different design?

ARGH

also, this occurred while in raleigh (car is now 130 miles from where i live)

DOUBLE ARGH
peter

E30m42cab · Mar 18, 2007

Could be a clogged rad, but not likely. can you confirm how hot the engine is actually running? Is the top rad hose getting way too hot? You may have replace the thermostat, but it might be malfunctioning, or even put in backwards. If you want, remove the thermostat completely and put the housing back together like normal, then find the two rubbber hoses on the firewall (driver side), and bypass the heater core by joining the two hoses together. run the car without those two things being in the way, and see what happens. Make sure your coolant doesn't have any air in to too... air pockets are famous for overheating problems. While you have the heater core hoses being bypassed, runs some water through the heater core from the engine bay and see if you have flow. The other thing is, my temp gauge on my old '86 325e was screwed up... it would go way up all the time, but it was just the gauge malfunctioning.

Z4madehere · Mar 18, 2007

Radiator and Heater Core both clogged?

Doubful, both your radiator and heater core are clogged at same time.

Is the thermostat mounted in the block on the 325i?

About the heater core:

The heater should work when the engine is warm and running, even if the thermostat is defective (stuck closed for example).

Detach the heater hose at the water pump and blow into it (heater hose goes from pump to the heater core then back to the engine block). First be sure to turn the heat lever on the dashboard to warm, else the line to the heater core will be closed.

If you can't blow any air thru the heater core, with the heat lever in the cabin set to warm, then your heater core is indeed clogged.

About the radiator:
The thermostat being stuck in closed position would definitely prevent water from flowing through the radiator.

I think your problem is some kind of vapor lock forming around your water pump when you put the coolant back in the radiator and the water pump is right in the middle of this vapor lock.

A water pump will not pump water if only air (vapor) surrounds it.

Report back with your result.

JoshIII
ID: Z4madehere
josh3i at hotmail . com

E30m42cab · Mar 19, 2007

Z4madehere said:

Uh, it's mounted on top of the engine, in a housing right before the top rad hose.

Why would you blow air through the heater core? He's supposed to be getting air out (which is probably the problem).... use water from a garden hose. The heat knob on the dash might not be opening the valve for the heater core, but this wouldn't make the engine over heat. I agree with Josh in that there's probably air in the system, or the thermostat is in backwards or stuck closed. Those are very easy things to check first.

ThunderChicken · Mar 19, 2007

the thermostat isn't stuck closed because it's brand new.....and i also tried running the car with the thermostat completely out (simulating the open position) and it still overheated. all the hoses are hot, but the rad and the core are still ambient temperature. also, in regards to the gauge itself, i've never had reason to doubt it before. it ran right in the middle just a couple weeks ago, and when it's in the red, the coolant is coming out the little release hose on the expansion tank. i bled the system to get the air out as well......

my guess is the core has completely clogged, preventing coolant from circulating at all.

next move is bypassing the heater core, and seeing if that restores flow.....

i'll do that garden hose thing too while i'm at it....

advance auto parts (and dealerships) sell this radiator flush substance, which is basically a type of drano that is safe for aluminum. anybody know if this works?

E30m42cab · Mar 20, 2007

ThunderChicken said:

The flush is probably worth the effort considering the effort it takes to put a new heater core in.

Let us know what happens.

Doughnut · Mar 20, 2007

what ratio of coolant to water have you put in the car? too little or even too much can cause the car to overheat.

Does the car get hot while your driving or does it only overheat while parked, another problem (ontop of your heater core being maybe blocked) is that the viscus coupling (clutch) in your fan has taken a shite?

Get back to me on that one. Also is that you with "the beast" in your avatar pic ThunderChicken?

jrt67ss350 · Mar 20, 2007

ThunderChicken said:

While the heater core may be blocked/clogged, it WILL NOT cause your car to overheat. I can wholeheartedly guarantee you that taking the effort to bypass the heater core will NOT fix your problem. Circulation of coolant in the engine does not depend on circulation of coolant through the heater core. Think about it - there is a valve in the heater core inlet tube under the dash that turns off flow to the heater core when the interior temperature selector is not set to heat.

If it is only overheating at idle, then it is most likely the fan clutch, just as Doughnut suggested. If it is overheating at idle and at speed, then it's either an improperly bled system that has a huge airpocket somewhere, or a clogged radiator.

ThunderChicken · Mar 20, 2007

First off, no, that's unfortunately not me in the avatar; it's Trey Azagthoth of Morbid Angel!

about the heater core.....i realize that flow doesn't necessarily depend on the core itself, but as far as I'm aware, when the selector is set to cold, the coolant is directly routed from the in tube from the engine, to the out tube which goes to the thermostat housing. so, if the core is clogged, flow would not occur when the selector is on hot. however, if i turn the selector to cold (and it works) it should bypass the core on its own.

this is going to be an interesting weekend........

jrt67ss350 · Mar 20, 2007

ThunderChicken said:

Nope. When the selector is set to cold, it closes a solenoid valve in the heater core inlet tube. The flow is NOT rerouted to the return tube to bypass the heater core. The coolant just doesn't flow through the heater core lines when the valve is closed.

These cars can get away with this because they have a bypass hose - that is the large hose that runs from the top of the thermostat housing over the top of the distrubutor and down to connect to the water pump. This hose allows coolant to circulate through the block when the thermostat is closed. If that hose was clogged, then it would cause the problems you are having, but there is essentially no way such a huge hose could be clogged - plus, you would had to have taken it off to replace the pump anyways.

ThunderChicken · Mar 21, 2007

crap....you're right.......

POOP

Doughnut · Mar 22, 2007

unlucky

ausman34 · Mar 24, 2007

I would say replace the thermostat but you have already did it. The symptoms that you are describing are that of a bad thermostat and it is possible that it could be the heater core. Did you bleed the system out? Let me know

ThunderChicken · Mar 25, 2007

Ah ha!

Finally she's fixed!

Here's what it was:

Air in system-bled coolant again, after flushing radiator, this time without trying to skip ahead and pre-fill the radiator seperately. i think i just created huge air pockets by doing that.............................DUMB

radiator sludge - flush with garden hose and soak with solvent from advance auto parts.

backwards hose - the upper radiator hose was on backwards.....pinching the thermo/pump hose slightly..........................I'M AN IDIOT

expansion tank cap too tight - before i replaced the water pump and gasket, i had a small leak coming from that area. to minimize coolant loss, i'd tighten the living hell out of the expansion tank, keeping the system at vacuum, so no fluid could escape. kind of like a new bottle of ketchup; it has a hole to come out, but it wont.

but when the new system would overheat (due to air pockets, mostly) it couldn't escape through the escape valve, and instead leaked out around the water pump seal (leaving more air pockets inside). miraculously i didn't blow the gasket though! whew!

thanks for the help everybody!! this would have been far more ugly (and probably expensive) without your assistance.

cheers!

Doughnut · Mar 26, 2007

First of all, congrats on the fix!
I'm interested about your "expansion tank cap being too tight" i dont think its possible to.... well it possible to over tighten it and strip the threads, but too over tighten it and block the valve on top from opening.... i dunno, what the valve does is just blow out coolant if it gets too hot, and regardless of how tight you tighten it, it will still blow.

get back to me on that one.

ThunderChicken · Mar 26, 2007

You are right on that account. But as far as I can tell, I didn't make it impossible to blow off, I simply made it harder to 'blow off' through the appropriate valve as opposed to the water pump seal. I didn't strip the threads, but I did get it to go down another good half turn, which i think caused it to go slightly below the escape hole, even when it develops an overpressure.

that wasn't so much the cause of the overheating, as an annoyance throughout the process which was aiding in my confusion and mis-diagnosis.

still overheating! YES!

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