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Old 01-10-2002, 04:04 AM
Registered User
Join Date: Jan 2002
Location: Coeurd'Alene Idaho
Posts: 48
coolant leak

Ok this site is way too much fun. 1st time Benz owner 89 300E I will run her till I die. Coolant leak gathers on the pan under the engine, approx 1/2 quart overnight. Pulled the pan, slow drip on front right side down the block. The AC compressor obstructs the view. Some moisture on the back side of the fan blades however the water pump, from what I can see is dry as a bone. Could this possibly be a core plug, backside of the water pump, or head gasket? (oil looks good). Any help would be greatly appreciated. We have a good Benz mech in town but like to try to solve mysteries on my own first. (stat housing is dry as well).

Thank you, Brian
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Old 01-10-2002, 10:07 AM
G-Benz's Avatar
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Join Date: Apr 2001
Location: Dallas/Fort-Worth
Posts: 5,711
The last time I saw that on my 300E, it was time for a new coolant pump.

Ironically, the coolant weeps out of the coolant pump and drips onto the block. It is very difficult to trace, and yes, the pump looks bone dry.

I had to wipe off the area and just stand there for several minutes and wait for the trickle of coolant to show up. Sure enough, eventually, it did, and when I placed my hand near the source, I caught drips coming from the pump (where you can't see it of course).

Mine didn't just collect on the belly had begun to puddle on the garage floor...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
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Old 01-11-2002, 02:07 AM
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Join Date: Jan 2002
Location: Coeurd'Alene Idaho
Posts: 48
89 300E coolant leak

G-Benz than you very much for your help, greatly appreciated.
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Old 01-11-2002, 06:16 PM
Steve Wengel
Posts: n/a
A coolant pressure tester is a BIG help in tracking down leaks. I got mine at Sears. They cost ~$75 but are worth it since you'll use it a fair amount. I think it was Benzmac who recently posted the right way to tighten hose clamps : pressurize the system and carefully tighten just the clamps where there is leakage, and just till the leak stops.

I found 3 completely unsuspected leaks in my cooling system (all hose clamps which APPEARED to be tight enough) when I used the tester.

Do not pressurize too high or you can blow out the waterpump seal.
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Old 01-11-2002, 08:14 PM
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Join Date: Jan 2002
Location: Coeurd'Alene Idaho
Posts: 48
Steve thank you for your attention. I just picked up my 300E this evening new coolant pump and all. The tech knows I like to tinker and ironically he suggested I should add a pressure tester to my tool collection. I guess 75.00 sounds like a lot however it sounds like this is a tool that will pay for itself in no time. Again thank you Steve.

Sincerely Brian
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Old 01-12-2002, 09:17 AM
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Join Date: Jun 2001
Location: Omaha, NE
Posts: 962
My pleasure Brian. A friend of mine recently told me he heard a lecture from a GM chief engineer, who said GM had done a large study to see what causes breakdowns on the road and leaves people stranded. By far, the top 3 causes were:

1. Tire problems (e.g., flats, slow leaks not caught in time)

2. Running out of gas (no surprise)


3. Cooling system problems.

This is why GM came up with the "limp home" mode on the Northstar engines, which allow you to drive them 50 miles with NO COOLANT at all. We don't have that luxury, of course, so my friend's point was that we all need to be mindful that small cooling system problems, like leaks, can turn into bigger problems if we don't catch 'em in time (he was lecturing me about my procrastination of in fixing a slow cooling system leak at the time!)
'93 400E
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