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rgnprof 12-14-2011 01:55 AM

Can't find the coolant leak - dripping from starter
Several posts on my most current situation - my '91 300CE (M104) overheated when radiator hose blew, replaced radiator and thermostat and then coolant started dripping from water pump. Just got done replacing the water pump - car runs great, temps are steady right above the 80C mark with no overheating, BUT I have a coolant drip from the rear driver's side, eventually drips off of the starter. Before, when the pump was leaking, the drip was coming from closer to the front, off the oil pan.

It is really hard to see under the intake manifold - and above the starter. Thought it might be the u-shaped hose from the crankcase to the oil filter housing or the heater hose at the very rear of the cylinder head on the driver's side - but I can't see any leaks from either. I'm at a loss...and, it doesn't seem to do it consistently - after a while, it will eventually stop. We are talking a small puddle under the car...

Any ideas? I'm thinking of trying to pull the starter and see what I can see...but I can't find good info on the coolant system on this car. I guess it's possible it's the new pump, but I don't see it.


porkface 12-14-2011 08:41 AM

head gasket, maybe? sure sounds like it. good luck, chuck.

POS 12-14-2011 08:52 AM

Fluid from the starter? You have a starting fluid leak! (Couldn't resist.)

All you can really do is take a strong flashlight and try to trace the source backwards. Removing parts without knowing where the leak is just wastes time and money.

Can't Know 12-14-2011 02:56 PM

Borrow a pressure tester and pressurize the system so it doesn't have to be hot. Then get lots of light and a good inspection mirror (the flexible kind on the long shaft). I'm with POS, no reason to start yanking stuff apart until you know what you're dealing with.

Another suggestion: clean that area of the engine thoroughly. After it's dry, toss some talcum powder back there; use a dry sponge to pick it up, the pat it onto all of the surfaces. Then pressurize the system. It will be lots easier to follow the trail that way.

Good luck.

glenmore 12-14-2011 09:20 PM

How long since the overheating?

My head gasket failure came a couple months after overheating (thermostat failure). Showed up as oil in the coolant tank.

porkface 12-15-2011 04:26 PM

i forgot to mention earlier-it MIGHT be the oring on the pipe, back of the head, where the heater hose attaches. i had 1 car, years ago, that'w where the leak shows up, off the starter. there's a plate that holds the pipe in and th oring is how the pipe seals to the head. everybody's correct, test-test-test. look carefully. good luck, chuck.

tbomachines 12-15-2011 06:00 PM

Heater hoses, including the heated wiper fluid line, head gasket (check for residue from HG itself)--also check oil for milky substance and antifreeze for sludge, and also isn't there a freeze plug somewhat above (but forward of) the starter on the M104s? Usually the antifreeze in these cars turns white and powdery as it dries up...a nice mess if your radiator ever blows :o

rgnprof 12-15-2011 10:00 PM

I found it! Or, I guess I should say THEM! Took it to a friend's shop today and put it on a lift. He has a really cool Snap-On flexible camera with a light on it and we were able to snake that around and find the first leak. It was coming from the elbow hose from the crankcase to the oil filter housing. The clamp was loose - so loose in fact, that we were able to rotate the clamp around so we could finally get a nut driver on the clamp and get it tightened down.

Pressured the system and let it sit for a while - no leaks. Took the pressure tester off and within a couple of minutes, it started dripping again in pretty much the same spot. So we started poking around again - removed the starter and found it. The pipe leading from the water pump to the oil filter housing was leaking right where the pipe enters the oil filter housing. I think I probably jarred this pipe just enough in replacing the water pump to break a seal - evidently it has an o-ring that seals it inside the housing. I don't really see how this thing seals - there is no bolt right there to tighten it down and it looks like it just sticks in to the oil filter housing. There is a small bracket that bolts to a bracket further down from the housing and it looks like that bolt was not fully seated properly....I think this is just a drain from the water pump...

I was going to replace the entire pipe as it looks a little corroded, but I couldn't find it online. Did find the o-ring though...

None of this was easy...but at least, it's not a head gasket - although with my luck I will probably follow Glenmore's experience - drive it for a coupe of months and then have the head gasket start leaking...


Early Bird 12-17-2011 01:47 PM

I have repaired this same leak few years ago on my 90 300CE. Cheap o-ring replacement, but a total PITA to get to (with starter on). Plus it took on and off months to locate this leak

rgnprof 12-17-2011 03:31 PM

I have no idea how you fixed this pipe without removing the starter - and I'm not even sure how you found it! I'm just hoping that it is just the o-ring...


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