3rdEye

Hey Guys,

Can't seem to find anything on this topic or I'm bad at searching, so I had my transmission rebuilt back in the summer at a local shop who had worked a couple c63s previously as well as other performance vehicles. Got my vehicle back about 2 weeks later, was very pleased with how everything was performing transmission was silky smooth, never felt like that in my 4 years of ownership. Put about 8k km on the car between July - November and put her away for winter, would take her out the odd day of dry weather to put through fluids and all the fun stuff about once a week.

Did some xmas shopping in the vehicle and noticed the transmission slipping again, forcing shifts at about 2k rpm, limped her home about 10 mins from the mall and had it towed to the same shop, they're saying the heat exchanger / radiator failed and allowed coolant to mix in with the tranny fluid, they want to replace rad + do several flushes on transmission before we would know if the transmission would need to be rebuilt again which they won't warranty as radiator is the cause of failure.

I can't seem to find anything on coolant being able to mix with transmission fluid or what type of signs would have shown to have the radiator fail, my car didn't overheat, all temps were always in range without issue and never had a check coolant level.

BLKROKT

That’s the only way that coolant and trans fluid could possibly mix so I’d be inclined to believe it.

dfreret

This happened to my 722.6 trans on my 2001 e55. common for the w210 rads back then. destroyed my trans and had to replace. Not sure if it's a problem with later cars, but I wouldn't be surprised it's still possible.

roadkillrob

Like the man said there is only one point of intersection between those 2 fluids.

3rdEye

Yea all signs point to unfortunately, could find quite a bit on it happening on w203 and w211 but not so much on w204 stuff.

See63Run

Totally different engine, but I had this happen on an old 4runner years ago. The radiator had an internal trans cooler and there was an internal failure and the fluids mixed. Pink coolant + red trans fluI’d = ‘strawberry milkshake’

roadkillrob

I think they are making good sense, if it was me, I would flush the living hell out of the cooling system and the transmission, replace the radiator and refill both systems and see how the transmission fairs, like you said you don't drive it much and you didn't drive around for 2000 miles after you noticed the slipping, so I suspect you noticed nearly immediately once some coolant mixed in and you are addressing it quickly before the water has a chance to cause much rusting inside the trans, so you may be good after a good flush and refill. Also nothing to really loose, do that and if it still slips then deal with the trans as it isn't adding much cost if it doesn't work and they have to drain the trans to rebuild and they have to flush it either way to know.

3rdEye

Update: From the shop, they don’t believe the radiator is the culprit as they’re saying there is separate transmission cooling lines and they’re saying the rad is fine. They’re not sure how or why it could mix but they’re saying it is a strawberry milkshake in the pan. They said I could do a tranny flush and see if it helps but they don’t believe it would.

What else could lead either water or coolant mixing with the transmission fluid, and would it still be a strawberry milkshake if the Blue ATF was used and could adding the red fluid cause these types of problems.

roadkillrob

Did the original shop use red fluid maybe as that would not be good and could cause it to look like red milkshake and cause it to slip. The only way coolant could mix would be in the trans cooler.

3rdEye

Im going to confirm tomorrow with the shop what fluid they used, but if they used red I imagine this might be what went wrong here, I don’t see how we could have a strawberry milkshake with blue fluid unless it’s a chemical reaction that causes it

roadkillrob

Yes that is where I am at - the blue fluid does not get red in any way I can think of and would need to be predominantly red to start, even mixing in coolant and even if your coolant is red, red coolant and green/blue trans fluid makes a different color than strawberry. I really feel like they filled it with the wrong fluid and if that is the case it will likely need a full rebuild again.

3rdEye

Shop is confirming they used red fluid but said the fluid they used was proper spec for my vehicle and it shouldn’t have any issues.

also saying that still doesn’t explain how water/coolant could have mixed in either.

back to square 1 🧐

C43 Fun Haver

i would ask if they have they trans fluid in bottles or bulk... if it's bottles.. ask if you can see one to verify the spec and color of the fluid. Everyone has already stated the only point of possible mixture.. As a parts advisor, people constantly put the wrong color fluid in..

roadkillrob

So can we go back to the start for a minute, was the assumption it was a strawberry milkshake because water mixed in or did they test for the presence of water. The wrong red fluid could look like a strawberry milkshake possibly without any water in the trans, so might be good to figure out if there is really water in there or if that was an assumption due to the look and color?