Why did my 2003 E500 engine dump coolant but pass pressure test?
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2003 E500
Why did my 2003 E500 engine dump coolant but pass pressure test?
I recently lost a serpentine drive belt while driving on a freeway due to the drive belt tensioner pulley bearings seizing up. I saw that the engine was overheating and pulled off the freeway. There was a trail of coolant behind the car and some coolant pooling on the lower left (driver's side) radiator rock guard.
I had the car towed home and got around to looking at it today. I added about a gallon of water before filling the coolant reservoir. I used a coolant pressure tester to pressurize the system to about 19 psi and expected to find a leak, but did not. The system held that pressure fine. Of course the engine was cold during this test.
Any idea what might have resulted in a coolant leak when the engine was overheating but not when cold? BTW, when I had this problem, I don't remember seeing any steam, just coolant on the ground and a bit in the area below the upper radiator hose and/or coolant reservoir hose.
I had the car towed home and got around to looking at it today. I added about a gallon of water before filling the coolant reservoir. I used a coolant pressure tester to pressurize the system to about 19 psi and expected to find a leak, but did not. The system held that pressure fine. Of course the engine was cold during this test.
Any idea what might have resulted in a coolant leak when the engine was overheating but not when cold? BTW, when I had this problem, I don't remember seeing any steam, just coolant on the ground and a bit in the area below the upper radiator hose and/or coolant reservoir hose.
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Joined: Jan 2014
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From: Republic of Texas
'99 and '05 E55 AMG
FWIW, if the reservoir cap is bad, it will leak pressure and coolant around the o-ring. Discernible by a white residue around the cap. If so, replace the cap.
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Joined: Jan 2025
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w164 ml350
Why -----as all you have to do is get off the couch and google a W211 cooling system or subscribe to MB WIS for a day and look at the rehms of specific documents pertaining to your VIN's coolant system and pay great attention to the plastic part of the system where you add water
Last edited by beef1020; Mar 19, 2025 at 03:41 PM.
Junior Member
Joined: Jan 2025
Posts: 21
Likes: 8
w164 ml350
There been multiple recent threads where you are the first to post and indicate that without codes it can't be solved, and yet I've managed to help them in some meaningful way to solve the issue. You're posts are low effort and offputting, if you want an active community then step it up and use your obvious knowledge to actually help. Perfect example:
https://mbworld.org/forums/e-class-w...n-t-drive.html
Last edited by beef1020; Mar 20, 2025 at 03:53 PM.
