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Burned Transmission Fluid

I took my BMW 325i to a local shop to have it checked out. The biggest issues that they found with it were fluid problems. They claimed that both the transmission fluid and the power steering fluid were burned and needed to not only be replaced but also needed to be cleaned with a service that they would provide for a few hundred dollars. If I didn’t they warned it could damage the transmission. They weren’t lying about the fluid, its old and its dark and it smells burned. My question is how bad is having burned fluid? I’ve done some research and I know that the actual fluid is damaging and it seems as though just replacing it doesn’t quite get rid of the problem. Is there any way I can run some sort of detergent through the transmission to clean out all the burned particles or is the shops information legitimate and buying their cleaning service really the way to go?

Unfortunately, there is no detergent that you can use to eliminate the damage caused by years of lax maintenance. And, once you see trans fluid that is dark and burnt-smelling, the chances of getting many more miles out of that trans are…not good.

However, I would recommend changing the fluid, and I would recommend that you go to an independent trans shop (NOT AAMCO, Lee Myles, Cottman, Mr. Transmission, or any other chain) for this service. If you are a particularly lucky person, the fluid change may allow you to get a bit more life out of that trans.

As to the PS fluid, I’m not quite sure how that would have gotten burnt also, but I guess that anything is possible. If you saw it and it was foul-smelling, then–yes–it should also be changed.

Just for future reference, trans fluid should be changed every 3 years or 30k miles (whichever comes first), even if the mfr does not list this procedure in its maintenance schedule. There is a trend toward car mfrs using “lifetime fluid”, but that terminology is essentially meaningless IMHO, and the fluid would still need to be changed on the above-noted schedule.

Many people never change their PS fluid. I do it every 60k miles, but I do tend to be a bit obsessive with maintenance.

“My question is how bad is having burned fluid?” Fluid may be burnt on normal mileage, but not usually, or if premature may represent a mechanical problem. I think you need a better analysis. Sure it is hard for a guy who used to be able to file a grievance for working conditions, who has had union rights taken away, seen earned income credit taken away, homestead credit taken away, cuts to cities counties shared revenue to fund rich and corporate tax cuts to ceo’s with insane bonuses to really want to help a probable republican with a bmw 325i, as most of us guys do not have bmw on our short list of vehicles.

“As to the PS fluid, I’m not quite sure how that would have gotten burnt”

Any fluid that’s used as a hydraulic fluid, ie; transmission fluid or power steering fluid, and when it’s put under pressure it creates heat. Over time this heating up of the hydraulic fluid causes it to oxidize or become burnt.


Model year? Mileage?

I agree with you, Tester, but I have personally never actually seen (or smelled) burnt PS fluid.
But, since I change my PS fluid proactively at 60k, maybe that explains why I have never seen it.

And, as Caddyman points out, since we don’t know the model year or odometer mileage of this mystery Beemer, we have no idea about how long its maintenance has been ignored.

Its a 1990 325i with 207k on its odometer. And to Barkydog: Registered democrat, picked up the car at a junkyard for 800 bucks and it is my first and only car. So I don’t have much information on how it was previously maintained. Besides these fluids the shop couldn’t find anything else major that was wrong with it so I might just change the transmission fluid and hope for the best. Thanks guys

Sorry Nolan, so much stuff going on in WI, I have some frustrations, and apologize.

Change the fluid, cross your fingers, pray to your favorite diety, and hope it works.

Unfortunately if the transmission is damaged it many times more than the value of the vehicle to fix it and not worth it likely.