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Old 11-29-2002, 07:43 PM
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Join Date: Jun 2001
Posts: 259
Water pump maybe?

The low water level came on in my 86 560 sl the other day, I checked the electrical connection, added a little coolant, light went out-end of problem. A couple of days later, the light came back on, I noticed some fluid on the garage floor, smells burned.
It cools perfectly, never overheats.

I got up under the car and saw no fluid anywhere on the hoses but a little on the middle of the subframe. I am guessing maybe it is coming out of the overflow from the radiator but would like to be sure.

Since it it cools fine, I am not real suspicious of the waterpump but would like to know how to troubleshoot to find out. No strange noises to speak of.


J. Boggs
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Old 11-29-2002, 09:05 PM
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Join Date: Apr 2000
Posts: 412
First clean all traces of coolant from the frame etc.Get the engine warmed up, shut it off and the pressure in the cooling system should build enogh to leak so you can find it, hopefully. If it is the water pump, it will be leaking out of the bearing where the shaft turns. Also you will feel some obvious play in the shaft. That sound about how my water pump started to go needing to be topped off more and more frequently.
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Old 11-29-2002, 09:52 PM
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Join Date: Feb 2000
Posts: 2,141
Chain auto parts stores rent cooling system pressure tester. I know of know better way to know for sure where all leaks are coming from, with the exception of a head gasket.

Very simple to use. Perform test on a cool engine.

I went thru a frustrating coolant loss problem on a 126 car and would never have found it were it not for this device.

My 2 cents.
Mike Murrell
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Old 12-06-2002, 05:51 PM
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Join Date: Jun 2001
Posts: 259
Rented a pressure tester and...

Engine not all the way cool, but my first test (if I did it correctly) points to air escaping from the neck of the overflow tank just below the lip. It looks like either someone already tried a reapair with some clear sealant around the neck or it is disintegrating a litttle.

If it is true, would it be possible to re-seal the plastic enough to hold pressure. Would a small pressure leak cause coolant loss even on the overflow? After driving the car, then opening the cap, there was some pressure built up.

Look for another leak, maybe? No coolant on the garage floor.


J Boggs
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Old 12-06-2002, 06:18 PM
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Location: Santa Monica, CA
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If what you are calling the overflow tank, is really the expansion tank (the pressure cap goes onto it), then you've found your problem. New tank (round or triangular) is $35-40.
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
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Old 12-06-2002, 06:53 PM
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Join Date: Jun 2001
Posts: 259
So proud of myself but...

I should have known it wouldn't be that easy. I pealed off some of the sealant and pumped it up again, it slowly bubbles off. I as I was going inside to look up how much replacement is, I noticed two puddles on the floor, one clear and probably off the extra overflow tube, but the other on closer insepection show coolant all over the oil pan. I don't see anything around the water pump but so I am hoping it's a radiator hose hose or transmission line or something. I am fearing a cracked block. Wish me luck on that.

J. Boggs
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