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Preventing Coolant in the Trans

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Preventing Coolant in the Trans

Post by Rangi246 » Sat Oct 13, 2018 9:41 pm

Hi everyone

Just wondering how many people here have had the coolant leak through the radiator/trans oil cooler into their automatic transmissions?

I've heard a few horror stories about how this can happen and it fries the transmission. I'm wondering how often this actually occurs? I know there was a problem on the early W211 E55 AMG Merc's and they solved it by replacing the radiator with an updated one.

As far as I can tell, the radiator in our car is the original one (86 635csi with 185k miles) and works perfectly but I was wondering if replacing it with a new one will help to prevent this happening.

I'm getting a bit paranoid on it and short of checking the trans fluid with a testing kit for water seepage every week, i'd much rather spend a few hundred on preventing it than having to spend a few grand on a rebuild.

Any thoughts on this?


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Ralph in Socal
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Re: Preventing Coolant in the Trans

Post by Ralph in Socal » Sat Oct 13, 2018 10:42 pm

Happened to my 85 Zinno. Radiator cooler for trans was severely corroded aftewr years of sitting. 5 trans fluid flushes did not help so I had to replace the trans

The bad thing is you won’t see the moisture in the trans fluid until it’s too late

A new radiator is under $200 and BMW maintenance requires coolant changes every 2 years anyway so it’s good insurance to do the radiator

There is a very fine line between "Hobby" and Mental Illness.

85 635csi Zinno Auto
84 528i Euro
83 635 Euro Arktik
81 528i Kastanien 5-speed
88 528e Bronzit (Granpa Car)
86 535i Auto (For Sale)
81 633 csi (retired)

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