My '09 GL320 Bluetec was just diagnosed with an oil cooler seal leak at 101K miles. The price to fix the (out of warranty) problem at the MB dealer - $4700 which includes replacing the intake manifold/swirl port motor (a "might as well" since they say these will fail too from coke/carbon build-up).

Seems these are getting common as some of the cars are breaking the 100K mark. Apparently the silicone gaskets fail from heat/age and start leaking. As I understand things, sometime later Mercedes changed to a Viton seal which will have much longer life.

Form discussing the problem with the tech at the dealer, it's not an "if" problem but "when" - says that all V-6 diesels w/ early silicone seals will need the service eventually.

So far - no luck on getting MB to foot part of the bill even though they acknowledge the problem is related to materials choice and/or assembly in a Technical Service Bulletin.

From everything I have read, it seems that the biggest part of this job is labor at MB dealer labor rates.
How bad is the leak? My shop told me I had an cooler oil leak, and based it on the oil from a loose oil filler cap.
I am sure at 110K miles mine is not dry, but it is certainly not leaking at a rate that justifies a $1500 to $4500 repair.


We have had a few people here do the work themselves, so it is certainly something that can be done by a competent independent at 1/2 to 2/3 the MB shop labor cost.


I know I have this repair in my future, buying the GL at 96K with the plan to get it close to 200K.

The diesel saves you on fuel but the maintenance appears to catch up to you. The gas engine in the GL, from what I've read on the forum, seems to be much more reliable. I've just read too many horror stories with the leaking oil cooler, manifold port motor, fuel line contamination, ETC, ETC. Makes me glad I chose the 450 over the 320 at the time.......though the extra MPG's of the diesel engine would have been nice.

where is the oil cooler and where do I check if is leaking?

I went with the diesel because I tow.

It is in the V of the engine and first sign on leaking is from the access hole at the bottom of the bell housing.


Those not familiar will suspect a rear seal leak.

An update - the oil cooler leak and associated problems have now resulted in the "check Engine" light being on constantly w/ about 15 faults, the biggest being related to the swirl port motors - dealer has escalated the repair price to $5400. Add to that that they say the heater in the AdBlue tank has failed - and that will cost $2000 to fix. On top of that, they say that given the age (4.5 years!) and miles, that they really aren't interested in doing the service.

Given that the book value of the vehicle is just a tad over $20,000 (109K miles), it simply doesn't make sense to spend that kind of money to keep it on the road - even though everything else is nearly mint (including $2000 worth of new tires).

Will investigate having an independent shop do the repairs, but only if they can give some nominal warranty on their fix. Seriously just thinking of selling the thing to a salvage yard for scrap value.

25+ year Mercedes owner, but the last few months probably means it's time to move to another marque. Makes no sense that a $65,000 vehicle can be reduced to scrap value in 4.5 years and a little over 100K miles. So much for the legendary longevity of Mercedes diesels.

I would LOVE to see a detailed estimate with parts and labor hours listed.

I just bought my GL with 85K a few months ago and it's caused me to be a regular on MBworld and Benzworld. My 08 ML320 CDI was bought new, so all the nuances with that vehicle I experienced...but it was flawless up to my trade-in with 88k for a pickup.

I was lucky enough to see the service record for the GL and my oil cooler and servomotor were changed at 79K and then a glow plug at 83k. It seems like the previous owner was tired of the immediate $$$$ pain and dumped it. I guess I was lucky that was done before I pulled the trigger!

Mine was bought with 96K and now has 113K.
I have a little seepage, but I don't know if it is the cooler or the turbo intake.
It is not enough to worry about yet (as it was well masked by the mess I made when I got the oil filler cap a bit crooked.


This summer I expect to drop the lower engine cover and do a thorough cleaning. I might even explore what I can with mu borscope camera.


I have a new turbo intake gasket to install and might try installing a oil separator on the crankcase vent.


I just find some the dealer service prices incredible. I understand it is a long job, but sounds like they want something over 24 hours in full price labor.
You can swap an engine for that.
If I do need a cooler gasket replacement an indy shop will get me business. Maybe one that will let me help.

I don't a have detailed breakdown, but the oil cooler and swirl motor service is about $5000, of which about $2000 is parts, and $3000 labor. MB apparently replaces the entire intake manifold assemblies rather than decarbonize them and just replace the motors - may make sense given the near $150/hour labor rate - that's pretty high to be cleaning crud out of an intake. The ADBlue tank heater replacement is about $1400 in parts and $700 in labor.

From what I understand, removing the intakes can be a bear as there are often a few studs locked in place by heat/corrosion. The MB book labor figure allows time for several that may have to cut off, remains extracted, etc. - of course, if that isn't needed, you pay for it anyway.

A few people here have done it themselves and no one has reported these problems.
(If) When I need to do it, I certainly will not be using a dealer.

When you factor in the extra cost of the diesel maintenance it negates any mpg improvements and then some of the gas engine.. Not only that, you also have to suffer through very weak acceleration with the diesel. I'm very disappointed because I love the idea of the mpg improvement.

I'm wondering if anybody can say definitively when the updated materials were put into production?

I bought mine for towing and would not trade the torque for any size gas engine.

I read 2010 on Wiki, but don't know how reliable the info is.

I bought mine for towing as well...I have a 24 foot trailer, 6500 lb fully loaded. My average tow is 4-7 hours so comfort and range matter. Compared to the Chevy pickup that I was using before, the GL is a dream to tow with. I was getting 9 mpg with the gas engine Chevy, and I get 15 mpg with the Mercedes pulling the same load. I'll take a little extra maintenance over that Chevy any day.

As if GL450 and 550 owners don't have maintenance. And what is this very weak acceleration suffering you speak of?

They are as slow as molasses off the line. Once you are at speed, it is tolerable. The maintenance on my GL450 engine has been very, very minimal: oil changes, air filters, and one water pump. I'm approaching 160,000 miles and it does not require any additional oil at 10,000 mile change intervals and runs as strong or stronger than it did new. The mileage has also improved a bit over time.

I was going to pull the trigger on a GL320 when I purchased my 450 and I'm glad I did not. There are too many stories of faulty/contaminated fuel systems, turbo seal failures, fuel filter issues, ETC, ETC. I know the diesel GL owners are very loyal but this engine in the GL seems to have far too many issues for my liking. I could tolerate the acceleration given the mpg if the engines did not have so many expensive issues.

Seems to me that people that say diesels are "slow as molasses" never owned a modern diesel vehicle. And as far as issues with GL320, I can say the same thing about GL450. You see a few GL320s with issues and think that all are like that. Just assures me that not getting a 450 was the right decision. I can't justify paying extra for maintenance and fuel.

I use my 2011 GL350 to tow a 7k lb Airstream. I just got back for a 2k mile trip and it towed awesome. Once you get the turbo spooled up it really does not work that hard to get going. That torque comes on strong and at low rpm. I am coming from a 3/4 ton suburban and while it was reliable it rode like a lumber wagon and got 9 to 10 towing, now I get 14 to 16.

I originally had a new 08 ML320 CDI and loved it. It got killer MPG on long trips and city and towed the crap out of it with a tandem enclosed and a 16' Cronkhite equipment trailer. Unfortunately, I treated that little beast like an old pickup truck so I traded her w/88k for a new Ecoboost F150 when it came out in 2011.

I loved that truck too, but then treated her like a car. My balance...get the diesel motor I loved on a bigger frame...the GL320. I kept my Kleeman KD-Box as I enjoyed it in the ML. It gave me more power and throttle response on the GL.

All vehicles, regardless of year/make/model have maintenance nuances. I know my SL600 will have issues with the hydraulic suspension. I also know my Silverado, with a 350, will need another intake manifold gasket job.

It's all part of owning cars...they require maintenance. However, if you are going to tow and want exception MPG for size/weight class...GL diesel all the way!

I had my oil cooler repairs and turbo seals repaired at my local Indy for $2200. The truck was leaking/burning oil. Now I'm doing 10K with adding a quart between oil changes.

There's a TSB regarding oil leaks from the cooler.
http://www.benzworld.org/forums/x-16...oler-leak.html

Case in point: https://mbworld.org/forums/gl-class-...nne-turbo.html

You don't have to own a GL diesel to know they are slow off the line. Just drive one for a little while and you will experience the difference between the diesel and the gas engines. Now, tell me all the issues you have seen with the GL450 engine? The GL diesel engine issues are very common but not so with the GL gas engines.