When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
'14 E350 with coolant leak. 36K miles. Don't really drive many miles but had to add coolant several times in the last month. Changed the oil/filter today and saw coolant accumulated in the bottom cover. I can see coolant has been slung onto the alternator and I see some around the water pump housing, but couldn't see exactly where the coolant leak is. I'm going to get it up to temp and system pressure and try to isolate the issue, but I'm having a problem believing the water pump would fail in so few miles.
Got a loaner from A Zone to pressurize the system and it looks like the thermostat housing is leaking, All I see is coolant coming out right at the bottom mounting bolt. Can't find anything leaking above that. At this point I don't know if it's just a gasket or the housing, so I'm just going to get replacement parts based on a worst case scenario.
Good you found the leak. So, you will replace the whole thermostat assembly or install a new gasket? When the thermostat goes you will get a CEL. Shame to replace the whole unit if it's just a gasket gone bad, but it's a pain to pull it and reinstall multiple times if it's not the gasket. Probably just spend the $150 and get it over with.
I just ordered the whole unit. I found an oem supplier part for $60 delivered. Should be here Wednesday. I can't imagine it's a gasket. It's the preformed stuff that fits in a grove and I've had to replace those before, but only after disassembly, never because of a leak. This should be a pretty quick fix unless the coolant hose gives me problems. Not sure whether or not I have to take the serpentine belt off, but if so, not a big issue.
No direct knowledge to share but looking at the WIS instructions it looks like you must remove the intake manifold to remove the thermostat housing, see step #3 in attached instructions. I know that the WIS instructions for removing the spark plugs also says to remove the intake manifold but you are able to remove the coil packs without having to remove it. It's just a more confined space but doable, hopefully this turns out to be the same way.
Post back your success story with a short tutorial for those of us that might face thermostat replacement down the road.
By the way, there are Youtube videos showing removal of the manifold if you have to do it, see here.
Thanks. I can't imagine why removing the intake would be necessary. I do see that in the photo inset, the serpentine belt is removed. I believe that will be necessary to pull the t-stat out of the timing case. I see the bolts are torqued to 8 Nm. I checked tightness to see if a loose bolt was the culpret and the bolts were torqued to a higher value for certain.
I'll follow up with install info. I need some reasonable temps and it's suppose to be pretty cold here until Thursday.
Update: The thermostat housing arrived yesterday (11/28) and it doesn't come with the O ring for the oil cooler coolant pipe. I couldn't find the part number for it so I went to the Wyler MB Dealer right down the road. I figured it was a $5 part but he said it LISTED for $15. Whew!!! He did knock it back to $12.75, but since I got home I've looked at a number of on line MB dealer parts sites and they all say the List price is $12. In reality, I couldn't have gotten it for less because they all charge $12-15 for shipping. I've never heard of or previously experienced a dealer marking up parts 25% over the list price. I'm going to be hesitant to go back there for anything else unless it is a must.
Installation will have to wait for another day with better temps.
Update: The thermostat housing arrived yesterday (11/28) and it doesn't come with the O ring for the oil cooler coolant pipe. I couldn't find the part number for it so I went to the Wyler MB Dealer right down the road. I figured it was a $5 part but he said it LISTED for $15. Whew!!! He did knock it back to $12.75, but since I got home I've looked at a number of on line MB dealer parts sites and they all say the List price is $12. In reality, I couldn't have gotten it for less because they all charge $12-15 for shipping. I've never heard of or previously experienced a dealer marking up parts 25% over the list price. I'm going to be hesitant to go back there for anything else unless it is a must.
Installation will have to wait for another day with better temps.
I always keep an o-ring kit around, for times like you mention. Can't tell you how many times it's saved the day. Sometimes you need a certain size/thickness/etc or specific material such as for a.c. systems, but in most cases the kit has provided the size needed.
I had gotten my kit from allorings.com but there are other vendors too.
I always keep an o-ring kit around, for times like you mention. Can't tell you how many times it's saved the day. Sometimes you need a certain size/thickness/etc or specific material such as for a.c. systems, but in most cases the kit has provided the size needed.
I had gotten my kit from allorings.com but there are other vendors too.
Good advice. You are correct, and I actually do have an O ring kit on hand, I just thought that in this instance, I might be better off with the oem part. My wife drives this car & I don't want any issues after a repair. I'd rather not have her tell me I should have taken it to the dealer & just paid the price & licked my wounds.
Got a break in the weather today, it got up to 50*, so I did the deed.
Here's the culprit.
There was a piece of foreign material either on the engine surface or on the gasket at the time of manufacture or the gasket was defective when manufactured. Either way, it should have been caught before it was installed.
As for how to replace the Thermostat and housing:
1. Disconnect negative battery cable
2. Remove the shields from under the engine and nose of the car.
3. Remove coolant reservoir cap
4. Drain coolant from radiator drain located on the lower driver side facing the fender.
5. Remove serpentine belt
6. Remove air inlet hose attached to the throttle body and air filter housing (there is a sensor and you have to remove the wiring connector).
7. Remove 4 torx screws attaching throttle body to intake. It is not necessary to remove the intake, you just need to massage the throttle body out of the way a smidge.
8. Remove electrical connector on top of t-stat.
8a. Remove radiator hose that is retained by a spring clip.
9. Remove 3 torx bolts that mount t-stat to engine (#27).
10. Remove bolt that holds oil cooler coolant line to t-stat. MB recommends replacing the O-ring. It lists for $12.
11. Move the throttle body slightly and maneuver t-stat out.
Note: If you want to make the job easier, you can remove the oil filter & give yourself more space.
Just do everything in reverse to complete the job.
Last edited by kp1; Dec 3, 2018 at 08:46 PM.
Reason: Forgot step to remove radiator hose
It's annoying, but cars are still machines with moving parts held together by screws and bolts and systems sealed by gaskets. Things break, wear out, and sometimes are defective. Issues have to be diagnosed and repaired, but I've never seen anything like the issue with that gasket. Odd that it took so long to develop into a full blown leak under pressure. Thank goodness AZone has that program to borrow the tools to make it simple to identify coolant leak locations.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
