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Took my 2013 GL550 X166 to the dealer to have the heater core replaced ($3k job) and asked the dealer to diagnose a coolant leak. Turns out coolant was leaking from 2 places: radiator and timing case. Replacing radiator, not horrible, about $1.6k... replacing the leaking seal on the timing case, $5.6k. DOH!~
Evidently, the entire engine has to come out to access and replace the timing case. I'm not inclined to pay that kind of money on a car I bought for $23k (86k miles) 4 months ago, so I'm trying to determine how likely it is (or soon it will be) that this leak will turn into something much worse.
Dealer says that there are 2 seals in the timing case... the 1st seal has failed and it leaking coolant. 2nd seal is intact. Dealer said that if the 2nd seal also fails, coolant will start to mix with oil, which will eventually destroy the entire engine (coolant mixed with oil reduced lubrication capabilities of the oil). Right now, dealer has found no evidence of coolant mixing with oil (no milky-looking oil). I have to add a little bit of coolant about once or twice every 5000 or so miles.
My current (wishful?) thinking is that the first seal was never supposed to fail, but it did and lasted 'til now (93k miles); maybe the second seal will last the next 93k miles or forever. I've never heard of this problem, and am not familiar with this part of the engine, so not sure if this is a reasonable line of thinking.
What do y'all think? Is coolant leaking in the timing case (but not yet mixing with oil) something you would A.) Definitely fix right now B.) Monitor for now, fix later C.) Not worry about it.
Last edited by Jason Stewart; Mar 17, 2021 at 02:49 PM.
Ask the dealer which seals need replaced. I see only one on the parts diagram. mercedesbenzstarparts.com
Ask an indy shop for a quote. I don't agree the engine needs to be removed. Engine removal is likely specified by MB / WIS. If you have the radiator replaced and the timing cover seal replaced at the same time, there is synergy in these jobs and potential for cost reduction.
Spoke with the dealer, and they provided this parts list as the things that they'd recommend to replace during a timing case reseal job. Evidently, the coolant lines in the X166's become very brittle with age and tend to break when you being to move things around in the engine bay, hence the multiple coolant part numbers you see.
GL550 X166 Timing Case Reseal Parts List from Dealer
So the dealer says a seal has failed, but you can see that it's failed, because there is another seal preventing failed seal from leaking.
The list is a laundry list of things "to do while you're in there". While not a bad practice to do preventive maintenance, the root cause seems fishy. I would either take it to an indy, DIY or just do the radiator replacement. The parts list also suggests they plan to remove the engine to do the front seal repair.
I read through several of the WIS procedures related to the front seal replacement, and it doesn't appear to me that MB specifies engine removal for this job.
Seems like a bad design. You could just do the seals that are leaking on the outside, but the dealer might have a point about the gaskets inside. If you are taking all the coolant hoses, water pump etc, you are not too far from taking the cover off and doing the inner seals, then again most people are not planning on doing this repair unless it’s too late and the engine bearings get washed. Hopefully the low coolant warnings will appear. IDK. Another item to keep an eye one yay.
I will be honest, if there is no evidence of coolant going into oil - no need to replace any internal seals. For me it is very strange to hear this whole story. Unless you have insurance company paying for it.
I did end up taking it to an independent mechanic and they said that my primary concern should be the radiator at this point. The said they radiator was leaking bad enough that they couldn't tell if there were additional leaks elsewhere. So, I'm going to start with replacing the radiator, then have them pressure test the system and see if they can replicate the timing seal leak. In the meantime, I will check the oil dip stick once a week to see if there are any signs of milkiness (coolant + oil).
In the meantime, I was able to find this Technical Service Bulletin that seems related to this topic:
YMMS: 2013 Mercedes-Benz GL550 Engine: 4.7L Eng
VIN: 4JGDF7DE3DAXXXXXX
OIL OR COOLANT LEAKING FROM TIMING CASE COVER PASSENGER CAR TECHNICAL TOPICS; JULY 2015
Reference Number(s): TT 07/15, Date of Issue: July 2015 MERCEDES-BENZ: Models "All with Engine M152/M157M278" GROUP: 01.40 - Crankcase, timing case cover, end cover
TOPIC
Oil or coolant leaking from timing case cover
CAUSE / EXPLANATION
The timing case cover has a drain hole that can leak oil or coolant when the front cover is not sealed correctly to the block.
CORRECTION
The drain hole is located near the thermostat piping. The drain hole is difficult to see and may be easily missed by technician diagnosing a coolant leak. Also the coolant may leak out of this location very slowly and not leave much evidence behind.
Resealing of the timing case cover has been successful in most cases. Only if there is a casting flaw in the sealing surface would replacement of parts be necessary.
I did end up taking it to an independent mechanic and they said that my primary concern should be the radiator at this point. The said they radiator was leaking bad enough that they couldn't tell if there were additional leaks elsewhere. So, I'm going to start with replacing the radiator, then have them pressure test the system and see if they can replicate the timing seal leak. In the meantime, I will check the oil dip stick once a week to see if there are any signs of milkiness (coolant + oil).
In the meantime, I was able to find this Technical Service Bulletin that seems related to this topic:
Yes, sounds like a solid plan, can you post the failure point on the radiator when you pull it. I have coolant smell and can’t trace the leak, I have not monitored consumption yet. The Inside seal I posted a pic off was not intended to fail anytime soon. I would also be worried of pressuring the system beyond its design in fear you will induce a leak in a very hard to service area. Again terrible design, coolant passages should be casted away from the crank case. Seals don’t last forever, and this is a failure point which can wipe out the bearings if it ever failed.
Yes, sounds like a solid plan, can you post the failure point on the radiator when you pull it. I have coolant smell and can’t trace the leak, I have not monitored consumption yet. The Inside seal I posted a pic off was not intended to fail anytime soon. I would also be worried of pressuring the system beyond its design in fear you will induce a leak in a very hard to service area. Again terrible design, coolant passages should be casted away from the crank case. Seals don’t last forever, and this is a failure point which can wipe out the bearings if it ever failed.
@Ricardoa1 Try smelling for coolant around the circulation pump. Often the are installed between the reservoir and radiator, often behind a headlamp on the side the reservoir is mounted. My circulation pump sends off coolant vapors and I can smell coolant when the engine is hot. No liquid drips, but there is a coolant crust on the hoses in the area. Use a bright light to see how all of the hoses are routed and connected.
I have not replaced the water pump on my gl550 yet. From looking at it, you can access without removing the engine. May be removing the front clip for easy access.
Just to put a bow on this thread for future readers... I had the radiator replaced and the system re-pressure tested... no sign of a coolant leak from the timing case cover. For now I am just going to monitor the situation by taking note of how frequently the car asks me to add coolant, and also keep an eye on the dipstick for coolant + oil milkshake.
What part of your radiator was leaking? i've been dealing with a strong coolant smell for past two years. Both times taking it in for service at dealer and no coolant leaks at all and pressure tested as well. Tech says my coolant lines are ok, and the smell of coolant is "Normal" smell. Shouldnt have a strong coolant smell after driving for 30 min and car is parked. I walk past front of vehicle and can smell coolant. Again tech says "Normal" to smell coolant. No leaks identified.
What part of your radiator was leaking? i've been dealing with a strong coolant smell for past two years. Both times taking it in for service at dealer and no coolant leaks at all and pressure tested as well. Tech says my coolant lines are ok, and the smell of coolant is "Normal" smell. Shouldnt have a strong coolant smell after driving for 30 min and car is parked. I walk past front of vehicle and can smell coolant. Again tech says "Normal" to smell coolant. No leaks identified.
@novae500 Try sniffing around the circulation pump, it’s probably behind the left/driver headlamp. The hoses on my W166 circulation pump “mist” or “sweat” and coolant smell is noticeable when the engine is hot. No wetness or drips, but there are signs of crusting and dried coolant vapor. Bottom line: poor design.
ONE MONTH UPDATE: No signs of additional coolant leaks since the radiator was replaced (no milky looking oil, drips under the car or messages in gauge cluster asking me to add coolant).
ding ding. thats whats going on with mine after looking. But dealer could not locate any leaks under pressure testing. So pretty much need to wait until it leaks for dealer to do something.
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