Oil Cooler leak
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Joined: Oct 2015
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From: South Florida (WPB
2008 ML320, 2004 BMW 540/6 sp., BMW R1200Rt motorcycle, Harley-Davidson Softtail Deuce, 1998 Hewes f
Oil Cooler leak
I have a 2008 ML320, 130,000 miles. A sudden oil leak showed up, and it leaked about a quart per mile before i got it home. The leak was coming from the block drain hole, down low, driver's side. The dreaded Oil Cooler Leak! It's apart now, and it has the "old" orange seals - hard as rocks. I suspected, from the volume flow of the leak, that the oil cooler itself was leaking, but I can't find any evidence of that. Don't want to buy a new cooler if I don't have to.
Does anyone know of an 'oil cooler leak' situation, where it was actually the cooler that was leaking? I'm looking for actual knowledge, not a situation where the dealer replaced the cooler, 'just to be sure,' while he was in there. (Cheap insurance, for him, as it was on the customer's nickel.)
Brucerman, in Florida
Does anyone know of an 'oil cooler leak' situation, where it was actually the cooler that was leaking? I'm looking for actual knowledge, not a situation where the dealer replaced the cooler, 'just to be sure,' while he was in there. (Cheap insurance, for him, as it was on the customer's nickel.)
Brucerman, in Florida
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Joined: Jun 2014
Posts: 507
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From: Massachusetts
2014 Smart ForTwo Passion Cabrio
I have a 2008 ML320, 130,000 miles. A sudden oil leak showed up, and it leaked about a quart per mile before i got it home. The leak was coming from the block drain hole, down low, driver's side. The dreaded Oil Cooler Leak! It's apart now, and it has the "old" orange seals - hard as rocks. I suspected, from the volume flow of the leak, that the oil cooler itself was leaking, but I can't find any evidence of that. Don't want to buy a new cooler if I don't have to.
Does anyone know of an 'oil cooler leak' situation, where it was actually the cooler that was leaking? I'm looking for actual knowledge, not a situation where the dealer replaced the cooler, 'just to be sure,' while he was in there. (Cheap insurance, for him, as it was on the customer's nickel.)
Brucerman, in Florida
Does anyone know of an 'oil cooler leak' situation, where it was actually the cooler that was leaking? I'm looking for actual knowledge, not a situation where the dealer replaced the cooler, 'just to be sure,' while he was in there. (Cheap insurance, for him, as it was on the customer's nickel.)
Brucerman, in Florida
Thread Starter
Junior Member
Joined: Oct 2015
Posts: 21
Likes: 1
From: South Florida (WPB
2008 ML320, 2004 BMW 540/6 sp., BMW R1200Rt motorcycle, Harley-Davidson Softtail Deuce, 1998 Hewes f
flybd5, thank you for the reply. Mine is a W164 ML320CDI. I was already very well aware of Brandon's thread; lots of good information in there.
I have the oil cooler out, and cleaned up. It's made of multiple aluminum plates, probably with channels machined into them, all brazed together, so the water goes between half the plates, alternately, and the oil goes through the other channels. I cannot see ANY gaps between the plates. I sealed my lips over one oil entry hole, put my thumb over the other, and blew hard. no leaks. I don't believe that brazed joints that have been tight for ten years would suddenly spring a leak. Much more likely that the rubber seals would leak.
Bottom line: unless someone on this Forum has evidence of an oil cooler actually leaking, I'm just going to replace the seals - with purple Viton, obviously!
I have the oil cooler out, and cleaned up. It's made of multiple aluminum plates, probably with channels machined into them, all brazed together, so the water goes between half the plates, alternately, and the oil goes through the other channels. I cannot see ANY gaps between the plates. I sealed my lips over one oil entry hole, put my thumb over the other, and blew hard. no leaks. I don't believe that brazed joints that have been tight for ten years would suddenly spring a leak. Much more likely that the rubber seals would leak.
Bottom line: unless someone on this Forum has evidence of an oil cooler actually leaking, I'm just going to replace the seals - with purple Viton, obviously!
Last edited by brucerman; Nov 23, 2017 at 09:14 AM. Reason: left out critical info.
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Joined: Dec 2013
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From: Bluffdale
2017 AMG C 43 (W205); 2019 E 300 (W213); 2008 ML 320 CDI (W164)
flybd5, thank you for the reply. Mine is a W164 ML320CDI. I was already very well aware of Brandon's thread; lots of good information in there.<br /><br />I have the oil cooler out, and cleaned up. It's made of multiple aluminum plates, probably with channels machined into them, all brazed together, so the water goes between half the plates, alternately, and the oil goes through the other channels. I cannot see ANY gaps between the plates. I sealed my lips over one oil entry hole, put my thumb over the other, and blew hard. no leaks. I don't believe that brazed joints that have been tight for ten years would suddenly spring a leak. Much more likely that the rubber seals would leak.<br /><br />Bottom line: unless someone on this Forum has evidence of an oil cooler actually leaking, I'm just going to replace the seals - with purple Viton, obviously!
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Joined: May 2015
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From: Miami, FL
2003 CL 600
It's unlikely that the coolers leak externally. I have seen them leak, but it's usually by mixing coolant and oil. The leak that you get outside the engine is always the seals, in my experience. '
You could take it and have it pressure tested, to be sure.
You could take it and have it pressure tested, to be sure.
