Yup497

Ive worked at several tire and auto places when I was younger and this does not look good to me. Isn't this coolant supposed to be blue? The dealer wants $250.00 for the full flush. I'd like to stick with OEM coolant. -2010 GL550

DennisG01

It would be blue if it was MB fluid (Pentosin?) But it could be a different color and still be fine. Are you 100% positive it's original? Meaning, you've had the car since new?

What color is it? All I can see is sludge and possibly moisture.

But, regardless, yes... flush it out. It's overdue.

eric_in_sd

Zerex G-5 is gold color.

The coolant is 150k mile life.

Yup497

Dennis- I haven't owned it since new however I do have the full maintenance records from the dealer. However who's to say it wasn't taken to an indie.

Eric- Would the coolant you mentioned register on a coolant tester? If so, I'd rather pay the $4 for the tester rather than $250 for the flush.

DarthVaderpa

Do the flush as soon as possible. If you still have that have a milky appearance after the flushing, you might have a serious problem. That is telling you that the oil and coolant of your vehicle’s engine mixing because the head gasket seal is broken. Stop driving your vehicle and get it fixed. The longer you drive it the more damage will occur.

Sudsy

While I am not a mechanic, I am an owner of a mechanics shop. Normally I am against an actual flush, a typical drain and fill is more than sufficient. In your case, pay for the flush, with that gunk buildup at the cap, makes me wonder what is in the rest of the cooling system. I would change the cap too.

eric_in_sd

The sludge is alarming. Are there any other cooling symptoms? How is the temperature stability? You can use either the dash display or connect a OBD module.

Possibly someone put an incompatible coolant (e.g. Dexcool) in and it's reacting with internal parts. That can make the sludge.

It could also be oil mixed in with the water. However, these are robust engines, so that would be unusual.

Zerex G-5 is HOAT coolant. I don't know what the story is on testing it. I believe the OEM coolant is HOAT also.

If you are up for it, I would try this: Drain the coolant. Fill with pure water. Leave idling at full operating temperature. Drain. Inspect the water. Save a sample if it's anything other than clean. Fill with G-05 (50-50 of course).

Note: You should also only use purified water ("distilled", most supermarket drinking water is RO filtered). Some tap water has contaminants that conflict with coolant.

DennisG01

Thinking more about this... maybe a better first step would be to get the system pressure tested - looking for possible head gasket leaks as mentioned above. Better safe than sorry.

chassis

Sludge=oil+coolant=leak somewhere

Yup497

Eric- I the display is always in the normal range and I've kept it on during driving and it stays in the normal range. You know St Louis weather is hot and humid during this time of year.

Dennis- when the engine is warmed up and at normal range of operation, I've squeezed the upper radiator hose and it seems to have great pressure. But who's to say that's accurate.

I am going to get the flush in 2 weeks. Eric I might try the water route though to see if its the gasket prior to getting the full flush. I pray its not a head gasket as the SUV seems to run great. No lights on the dash etc. *knock on wood*

chassis

Diagnostic tests and observations can affirmatively confirm or deny a cylinder head gasket leak. Most of the behaviors listed below will not generate a check engine light:

- cylinder compression test
- rough idle, either continuously or only upon cold start
- white smoke/steam from tailpipe or sweet smelling exhaust from tailpipe
- coolant system pressure decay test
- visual (scope) inspection of cylinders/pistons to check for "washed" pistons
- visual comparison of spark plugs for non-uniform appearance
- radiator cap visual inspection for sludge
- oil fill cap visual inspection for sludge
- external oil weeping from cylinder head interface with engine block
- coolant contamination in oil upon oil change
- oil contamination in coolant upon coolant change
- increased oil consumption
- coolant consumption (repeatedly low or empty surge tank that requires topping up)

DennisG01

You are correct - simply squeezing the hose doesn't really tell anything. A pressure test is a relatively simple procedure and any halfway decent local garage can do it in short time. It's possible you may have to dive into it further, but the basic analysis is pretty straight forward.

EDIT: Fixed some of my bad typing... sorry about that!

Yup497

Thanks for your help Dennis. I'll make a trip up to my local tire and auto place where I have a couple friends that work there.

lkchris

A common failure on these engines is the gasket between the oil filter housing and the engine oil cooler. The cooler works by transferring oil temperature to the coolant, which is colder. This is oodles and gobs more likely the cause of coolant/oil mixing, than for example a head gasket leak, as those are less failure prone.

fwiw the coolant change interval given no contamination and still original coolant is 15 years ... any miles.

you can read more about the gasket failure here

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

factory fill coolant changed from gold to blue in maybe 2010. Gold Zerex G-5 is NOT a suitable replacement for blue. There’s a blue Zerex replacement instead.

DarthVaderpa

According MB, coolant must be replaced every 143000 miles or 15 years. This is how it looked after 50000:


You can buy the OE coolant, Q-1-03-0004 (325.0), almost anywhere, FCP, Amazon, even in Walmart. Just stick with the original.