Repair-It

I guess that isn't much direction then. Hope it isn't the turbo coolant line O-rings.

It’s now parked on the lift and out of commission until I can get it straightened out. I think I’ll also try to go after the oil leak at the back of the drivers side head while I have it down for service.

I ordered another coolant pressure test kit that hopefully has the right cap that should come in late today, but I’m tied up at work in MA tomorrow and I’m at a scout campout tomorrow night through Sunday morning. I should be home by 9:30 or so on Sunday.

If you had any time available Sunday to help me track down the coolant leak and/or try to figure out what gaskets or similar to order for the vacuum pump (assuming that’s my oil leak), and if the coolant leak isn’t too bad we could also troubleshoot the waste gates/turbo code it would be a big help.

kevm14 wrote: Wed Nov 12, 2025 8:32 pm I guess that isn't much direction then. Hope it isn't the turbo coolant line O-rings.

I think those are “inboard” of the heat shielding, so hopefully not the source.

I bought blue/green G48 coolant for the mini-Benz. Is it ok to change over the GLS550 to the same stuff or should I try to find Benz-approved pink?

I have about a gallon and a half, but I was going to order enough to fully refill in case I use some water for troubleshooting and then have to fully drain/replace.

https://www.walmart.com/ip/Zerex-G48-Lo ... /173296399

Looks like confusing info. I guess I should try to find pink.

https://operatingfluids.mercedes-benz.c ... t/310.1/en

I guess G40 it is.

They changed from G48 to G40 somewhere in the 2015 timeframe if I recall. G40 is driven by environmental regulations though. In theory a flush to pure G48 may be the way to go but don't mix.

rpaoness wrote: Thu Nov 13, 2025 5:57 am It’s now parked on the lift and out of commission until I can get it straightened out. I think I’ll also try to go after the oil leak at the back of the drivers side head while I have it down for service.

Could be that centrifuge cover. It's a bit involved to replace (they want you to come in from the bottom) on the X166 and I'm sure you don't have the part in hand anyway.

I’m guessing I’ll have to order something for the coolant leak, so I’m just assuming it will be down until a part order.

Got the pressure tester in and jacked it up to 12psi or so. Only lost about 2 psi in an hour, but there was coolant leaking again. Traced it so far to the heater hose that's under the cowl. Yesterday I only looked at the engine-compartment-to-cowl hose/plastic fitting. With the plastic cowl cover over the master cylinder removed I could see far enough in to see a drip coming down the hose connection under the cowl. I need to figure out how to get more of the cowl off to possibly access where it is. Hopefully some of that stuff comes off.

Pull the seal and the panel should be removable.