Preemptive maintenance paying off - failed o-ring
08-23-2018, 02:15 PM
#1
MBWorld Fanatic!
Thread Starter
Join Date: Jan 2014
Location: Republic of Texas
Posts: 3,218
Received 928 Likes
on
720 Posts
'99 and '05 E55 AMG
Preemptive maintenance paying off - failed o-ring
I've been pulling a major maintenance now that my E55 is at 150,000 miles and will soon post in-depth about it. This post contains an example of why I perform regular and comprehensive maintenance.
Over the past few months, after parking the car on a very hot day (~100 degrees F), the next morning I would occasionally find a few drops of coolant on the ground behind the driver's side front tire. Maybe once every 2-3 weeks and even then not much coolant. But it's not supposed to be there! I was having no luck locating the intermittent leak.
A day or so ago, I pulled and replaced the water pump (good thing as the seal was showing signs of leakage), and, in preparation for filling the cooling system with fresh coolant, connected the vacuum fill apparatus (one pulls a vacuum in the area of 30 kPa in the system, then open a valve to a hose in a bucket of coolant. Atmospheric pressure will literally push the coolant into virtually every nook and cranny of the cooling system), and initiated the process. I was aiming for ~30 kPa but around ~70 kPa the system suddenly returned to 101 kPa (atmospheric pressure). Uh-oh. That's not good. Now I had to locate the leak so I filled the system as best as possible with coolant, screwed the cap on tight, cranked the car to warm the coolant and increase system pressure, and...boom! Major leak dripping behind the driver's front tire from the fender liner. It appears my former intermittent leak was caused by a failing o-ring on the heater valve that fully failed when I pulled vacuum for the coolant refill.
So, the leak was from a 13-year-old o-ring on the heater valve. The coolant would drip out of the valve, collect in the metal trough in front of the windshield, and flow towards the driver's side where, under the SAM, the coolant would drain through a small hole in the sheet metal located behind the fender liner.
So, an o-ring worth a few cents failed while I was performing maintenance and *not* 300 miles into a 500-mile road trip. New heater valve enroute for $41 and I'll be replacing it this Saturday. FWIW, if one removes the entire windshield wiper mechanism (2 nuts and 1 bolt) it is much easier to access the heater valve. If I had the o-rings on hand I would have just replaced the o-rings.
PS. Do you realize how easy it is to remove the alternator once the water pump is off the engine? If you are replacing the water pump, that is the time to pull the alternator and replace the voltage regulator/brush assembly!
Over the past few months, after parking the car on a very hot day (~100 degrees F), the next morning I would occasionally find a few drops of coolant on the ground behind the driver's side front tire. Maybe once every 2-3 weeks and even then not much coolant. But it's not supposed to be there! I was having no luck locating the intermittent leak.
A day or so ago, I pulled and replaced the water pump (good thing as the seal was showing signs of leakage), and, in preparation for filling the cooling system with fresh coolant, connected the vacuum fill apparatus (one pulls a vacuum in the area of 30 kPa in the system, then open a valve to a hose in a bucket of coolant. Atmospheric pressure will literally push the coolant into virtually every nook and cranny of the cooling system), and initiated the process. I was aiming for ~30 kPa but around ~70 kPa the system suddenly returned to 101 kPa (atmospheric pressure). Uh-oh. That's not good. Now I had to locate the leak so I filled the system as best as possible with coolant, screwed the cap on tight, cranked the car to warm the coolant and increase system pressure, and...boom! Major leak dripping behind the driver's front tire from the fender liner. It appears my former intermittent leak was caused by a failing o-ring on the heater valve that fully failed when I pulled vacuum for the coolant refill.
So, the leak was from a 13-year-old o-ring on the heater valve. The coolant would drip out of the valve, collect in the metal trough in front of the windshield, and flow towards the driver's side where, under the SAM, the coolant would drain through a small hole in the sheet metal located behind the fender liner.
So, an o-ring worth a few cents failed while I was performing maintenance and *not* 300 miles into a 500-mile road trip. New heater valve enroute for $41 and I'll be replacing it this Saturday. FWIW, if one removes the entire windshield wiper mechanism (2 nuts and 1 bolt) it is much easier to access the heater valve. If I had the o-rings on hand I would have just replaced the o-rings.
PS. Do you realize how easy it is to remove the alternator once the water pump is off the engine? If you are replacing the water pump, that is the time to pull the alternator and replace the voltage regulator/brush assembly!
Last edited by bbirdwell; 08-23-2018 at 02:18 PM.
08-23-2018, 02:24 PM
#2
MBWorld Fanatic!
As always a wealth of information! This is a great idea, People can avoid costly repairs later if they just maintain their cars right.
08-23-2018, 07:37 PM
#4
MBWorld Fanatic!
Join Date: May 2018
Location: Jakarta-Indonesia
Posts: 3,892
Received 3,978 Likes
on
2,323 Posts
2014 - W212 - E400 ( M276.820, 3 liter Turbo) RWD not Hybrid
O-ring is a wonderful engineering product, but it has a finite life.
When I dive, my life depends on a few o-rings for my breathing regulator and the scuba tanks.
But annual overhaul I do and fresh o-rings every year, no issue. All o-rings accessible for tear down.
In a car engine and all other components of a car using o-rings, a US$1 o-ring deep inside a component difficult to access may need US$1,000 or more in labor to replace, that is a long term worry....assuming we know
what components uses o-rings and we find ways to be preemptive like bbirdwell vacuum test.
However some components with o-rings, we can not do any vacuum or test pressure on it.
I don't know what kind of oil pan is you guys have on your E55 engine , but there is one video you guys should watch if you oil pan is like the video below, its o-ring based disaster waiting to happen :
When I dive, my life depends on a few o-rings for my breathing regulator and the scuba tanks.
But annual overhaul I do and fresh o-rings every year, no issue. All o-rings accessible for tear down.
In a car engine and all other components of a car using o-rings, a US$1 o-ring deep inside a component difficult to access may need US$1,000 or more in labor to replace, that is a long term worry....assuming we know
what components uses o-rings and we find ways to be preemptive like bbirdwell vacuum test.
However some components with o-rings, we can not do any vacuum or test pressure on it.
I don't know what kind of oil pan is you guys have on your E55 engine , but there is one video you guys should watch if you oil pan is like the video below, its o-ring based disaster waiting to happen :
08-24-2018, 09:07 AM
#6
MBWorld Fanatic!
I had to replace my oil return line o-ring, as they were hard and brittle, and leaking oil from the block. 
08-24-2018, 10:46 AM
#7
MBWorld Fanatic!
Thread Starter
Join Date: Jan 2014
Location: Republic of Texas
Posts: 3,218
Received 928 Likes
on
720 Posts
'99 and '05 E55 AMG
Please tell me more! It doesn't get cold enough here to freeze the windshield washer tank. Heck, a hard freeze here is 28 degrees F (-2 degrees C).
Trending Topics
08-25-2018, 12:08 PM
#9
MBWorld Fanatic!
