I am having a cooling issue with my 89 325i and am looking for
ideas. I removed the thermostat yesterday to rule it out. I believe I
am either looking at a plugged radiator or a faulty water pump. I am
pretty sure the system is well bled so that isn't the issue.
The problem has came on slowly and not all at once. I am running
well over normal temp at various times. The car also gets warm very
quickly when it's first started up. All of this is reading on the
guage and I haven't actually lost any coolant due to overheating. Is
there a way to actually check the water pump? I thought about running
some radiator flush through the system but I'm not sure it would do
any good. How do I go about diagnosing this without throwing parts at
take the hoses off the heater core and turn it over or start it for
just a second... you'll quickly see if it's pumping coolant around.
also check and make sure your fan clutch works... warm the car up to
mid-range on the temp gauge and get a pencil or small stick or
something and stick it in the fan blades... they should not slow down
or stop... if they do then you need a fan clutch. in my e30 the a/c
doesn't work so I just took the compressor belt off and hit the a/c
button... this will make the secondary electric fan run which will help
cool the engine.
The fan clutch will not cause the engine to overheat "quickly" as the OP
wrote. It will also only allow the engine to overheat when the car is
driving very slowly or stationary. Any time it is moving it will have
enough air flow to keep it cool.
Unless you have some serious goo in the cooling system (you haven't been
running that Prestone crap have you?) in all liklelyhood the problem is
the water pump. The only other explanation would be the radiator is
blocked with crud.
Buy a waterpump (pretty cheap on E30's). When you drain the engine to
replace the pump, backflush the radiator with a garden hose. Just pull
both the big coolant hoses from the radiator off the engine side and
direct your garden hose into the bottom one, letting the water flow out
the top one. I usually seal the garden hose in with a rag wrapped
Put (good) new coolant in.
Well, here's the diagnosis so far. Water pump replaced, impeller on
old pump had 1/4 inch gap between pump and housing compared to new
pump. Obviously, they don't work very well when the water just swirls
back around the impeller. Radiator flows water through it very well.
Flushed all of the old coolant out and didn't see anything
unusual.Will have a better idea tomorrow if the problem has gone
Final diagnosis of this problem. Running down the road today, the
car stays very cool however as soon as I start sitting still, the temp
starts to climb. I popped the hood and stuck a pen into the fan only
to find that the clutch has gone bad. I'm a bit annoyed as the damn
thing is about six months old (replaced it once before due to
overheating issues an d the problem partially went away). Looks as
though I'll either be fusing the clutch to make it a continuous fan or
I'll be replacing it with an electric unit. The electric is the better
choice as it takes less in the form of horsepower to operate.
I won't say that your fan clutch hasn't gone bad again, but don't forget
that you already have a 2-speed electric fan on the E30. And it should
be seeing some action if your temperatures are climbing above 90 C.
Well, you seem to have had more than one problem, eh? The overheating
is gone now except when at a standstill.
I would try fusing the clutch somehow myself. The amount of horsepower
consumed by the fan is not all that much, especially when moving along
briskly and getting good airflow through the radiator. Also, even an
electric fan will consume horsepower through the alternator. Plus the
added load on the alternator may cause that to fail more often, and the
aftermarket electric fan motor may crap out some day. I prefer things
simple and mechanical, myself. YMMV...
Well, another thought on this. Fusing the fan MAY cause it to loosen
and possible spin off into the radiator when the engine is shut off.
After having this thought, and the fact that my first attemp at fusing
the fan didn't work, I decided to go electric. Damn difficult to find
a fan that will fit between the radiator and the motor. Not much room
there at all. Having mixed results at cooling as the thermostat switch
I got doesn't seem to be very effective. When wired to come on with
the key, I still slowly heat up to an undesired temperature. Might be
because I don't have a thermostat installed at the moment or possibly
even an air bubble in the system still. The aux fan seems to have a
bad thermo switch so it's no help either. Why does this have to be
such a pain in the ass???
On Thu, 02 Nov 2006 14:49:15 -0500, Fred W
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