Galstaff

Seeing as this is my first post I'll try to include some history. I bought my 2007 GL450 two years ago with about 136,000 miles on the odometer. I have since been lurking around this website gleaning many useful insights and have done all of the maintenance and repairs thus far. Last year in May the thermostat gave up the ghost and the high temp light came on while my wife was driving. I'm not sure how long it was driven like that. I replaced the thermostat and we had been driving it without issue. It has about 164,000 miles now and I discovered coolant on the dipstick yesterday after the low coolant notification came on. I also replaced the oil filter housing gasket when doing the thermostat. I'm thinking a head gasket has failed and was hoping for a replacement guide or video to walk me through the process. Any sage advice is also welcome. Thanks to everyone in advance!

DennisG01

Are you sure it's coolant? It would usually just be mixed in WITH the oil and not separate - unless the car has been sitting for a long time where the coolant and oil separated. But then the oil would be on top and as you pulled the dipstick out, the rest of the dipstick would have gotten covered in oil on the way out. Or, at least, that sounds reasonable?

Are you sure it wasn't just moisture?

On the flip, side, obviously your coolant is disappearing somewhere. But maybe, just to be sure, get the oil analyzed? It's pretty cheap to do that - either search for a local CAT store or send it to a place like Blackstone labs.

Just some thoughts!

Galstaff

That is a valid money saving tip. I did check the oil fill cap and opened the filter housing and didn't see any evidence of coolant either place. I've had a head cold for two weeks so my super sniffer isn't as keen. I'd planned on smelling the dipstick when my sinus cleared as I'm excellent at smelling coolant due to my sweet tooth. I'll keep investigating and see if there are any local places that can do the oil analysis.

lkchris

A typical cause of coolant in motor oil on the M273 engine is failure of the gasket between the oil cooler and the oil filter housing. The oil is cooled via heat transfer to coolant in this cooler. It’s covered in this article

https://blog.fcpeuro.com/the-definit...d-m273-engines

chassis

Keep an eye on things over time and post photos and observations.

Classical tests to definitively diagnose head gasket failure:

- compression test
- leakdown test
- coolant system pressure test
- sweet smell from tailpipe
- gurgling sound in cabin from HVAC
- poor or erratic cabin heating behavior
- bubbles in coolant reservoir
- chocolate milk substance on oil fill cap
- irregular spark plug color
- “washed” pistons from coolant in combustion chamber
- rough idle
- check engine light or error code such as misfire
- decreasing coolant level over time

When the preponderance of data from some or all of the tests points to failed head gasket, then it’s a failed head gasket.

Galstaff

Well I gave the dipstick the old sniffer test, and took a whiff of each exhaust pipe (which was awful) and I think that I just panicked initially and it most likely is some moisture from sitting. I do still need to track down the leak, but I'm less freaked out than I was the last couple of days. I'll start going down the list and see if I can get it figured out, and get the oil in for a quick check. Thanks to everyone for the great tips and the common failures link.

chassis

Forgot two more:

- coolant in oil when drained into catch pan
- steam from tailpipe at idle with warm engine

tadiguy

Exactly how did the coolant look like on the dipstick? What does the exhaust smoke look like when you first start up?

Coolant in the oil will usually froth up the oil as the oil circulates. You'll see this frothy/slimy "stuff" on the dipstick and sometimes in the oil cover/cap as well, especially if it's a lot of coolant. Either way having the oil analyzed is a good first step. In addition you could also do compression test (with adjacent plugs taken out) to diagnose head gasket leakage. Given how easy it is to access the plugs it will be worth a check. Also inspect the underside of very carefully to see if you find an alternative reason why coolant is low. I've seen some wetting around my lower radiator hose that I plan to address in the spring when the weather begins to warm up since it's not leading to coolant loss.

Galstaff

The dipstick had a light coating of what could be described as sour cream mixed with oil color. It was on the shaft of the dipstick as well as a bit on the very end. I've definitely seen the same thing with oil mixing in water before. The exhaust starts as a nice white color but is not overly thick. After a minute or two there is very little visable exhaust. Neither the dipstick nor the exhaust have a sweet smell. I'll want the oil test just to satisfy my mind. I have all the tools to run through some basic plug and compression checks to see if I have a noticeable loss of compression or coolant scrubbing a cylinder.

chassis

If you work through the list of tests, you will discover the answer to whether or not the head gasket is blown.

Coolant loss over time means coolant is either leaking out of the system or being consumed inside the engine. Leaking is generally easy to see drips somewhere. Consumption needs a more thorough diagnosis.

tadiguy

Sorry to say, but this is not a good sign given the loss of coolant and previous overheating... If it's head gasket hopefully the head is not warped so it will be a simple gasket change. Good luck and let's know how it goes.