Cooling system PROBLEM!!! - PeachParts Mercedes-Benz Forum

racerx12367 · #1 08-01-2011, 11:26 AM

1992 300e The cooling system isn't working. I have tried taking out the thermostat, replacing the thermostat. The pump isn't leaking or making any noise. I have now removed the radiator to see if its clogged, it seems to be fine. I 've taken the serpentine belt off and the water pump feels okay. Also when the pump is spun by hand the coolant in the thermostat housing appears to move through the engine. I've also checked the fan, it spins about 1/3 of a revolution. I really don't think that the pump is shot, but I don't see what else it could be. What else should I check before I start ripping into a tough job.

Thanks in advance
Dan

oldsinner111 · #2 08-01-2011, 11:40 AM

head leak?Weak hose being suction in.

racerx12367 · #3 08-01-2011, 12:09 PM

It doesn't seem to be leaking at the head, I'm not losing any coolant. The hoses look okay too.

engatwork · #4 08-01-2011, 12:20 PM

What kind of temp readings are you getting?

racerx12367 · #5 08-01-2011, 12:55 PM

The gauge is pegged. The radiator when its done that has been cool, it doesn't appear to be flowing. The tank is full as well. Have also installed new cap and temp sending unit.

engatwork · #6 08-01-2011, 01:17 PM

The radiator should be pretty hot to the touch. Sounds like you are on the right path in regards to no flow. Was their any visible build up in the radiator? How did you check for flow through it? Did it just start doing this all of a sudden or did the temp creep up till it got where it is today?

oldsinner111 · #7 08-01-2011, 01:27 PM

thermostat?

racerx12367 · #8 08-01-2011, 01:32 PM

No there wasn't any build up on the radiator that I could see. I took it (the radiator) to work and blew it out with air. I also capped off the inlet and the opening to the reservoir and blew it out that way as well (100 psi). No debris at all and good air flow. It sounds of though you're thinking the water pump (what else could it be at this point).
I don't see what could be wrong with it, its not leaking, it doesn't wobble, and its only an impeller. Any clues as to what would fail?

oldsinner111 · #9 08-01-2011, 01:34 PM

Maybe water pump impeller broke off clean.

racerx12367 · #10 08-01-2011, 01:46 PM

I guess that I will replace the pump...from what I've read its a real bear of a job. Thanks for your help, I'll let you know if its a happy ending or not.

Thanks again
Dan

Hirnbeiss · #11 08-01-2011, 02:30 PM

Check the fan and fan clutch too. The fan should "whoosh" when it's hot and you accelerate from idle.

Is it possible you have air in the system? I think 104's have bleed screws in the block. Also, see if you get heat from the heater core.

A symptom-free pump failure just doesn't sound right, especially when you get results with your hand test.

Here's a pretty thorough link (for Honda's) jsut to make sure you've covered all your bases. It shows a corroded impeller, but notes that this is a very extreme case.
http://www.tegger.com/hondafaq/overheating/index.html

racerx12367 · #12 08-06-2011, 06:14 PM

I was still pretty skeptical about the water pump being the problem. After checking many old posts I thought that the radiator made the most sense.
I just finished replacing (supplied by Phil) and it worked like a charm. Now the temp stays at the 80° on the gauge. Thanks to all who helped me on this frustrating problem.

big dog 2 · #13 08-07-2011, 12:49 AM

I suspect the fan clutch may be the culprit too!

benzme · #14 08-07-2011, 09:30 AM

Just to help with my own diagnosis - when you say it stays at 80, is that in stop start traffic as well?

Thanks

mpolli · #15 08-07-2011, 12:27 PM

Ummm.. I think it's fixed