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  • September 20, 2019, 01:41:04 AM

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Author Topic: Mixed Brake Fluids  (Read 228 times)

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Online MIPS

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Mixed Brake Fluids
« on: June 16, 2019, 04:54:25 PM »
When my rear diff was rebuilt they also serviced my rear drums and topped off the reservoir. I was inspecting the fluid level today (no leaks or braking issues, just checking it) and found there's at least two separated liquids in the master cylinder which I suspect is two different brake fluids.

The master cylinder has a label indicating you must ONLY use Dow Corning (or equiv.) DOT5 but the reservoir cover says to use DOT3 only and I'm aware that mixing the two is a very expensive mistake. I can pump the reservoir out but what should I be refilling it with on assumption I don't also have to bleed and purge everything else?

Edited: I just verified with the mechanics book and it too asks for DOT3, so now I got two items stating to use DOT3 while another says DOT5. The reservoir is now drained and cleaned but I'm hesitant on adding anything.

« Last Edit: June 16, 2019, 05:31:12 PM by MIPS »

Offline AMC of Houston

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Re: Mixed Brake Fluids
« Reply #1 on: June 16, 2019, 05:10:57 PM »
DOT 5 (silicone base) should never be mixed with anything glycol-based (Dot 3, 4, & 5.1).   Is the sticker for sure DOT 5, and not 5.1?

Flush her out with DOT 3 or 4 and you're good.
George G.
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Online MIPS

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Re: Mixed Brake Fluids
« Reply #2 on: June 16, 2019, 05:30:37 PM »
It's clearly DOT5 alright. I'll go and get another two or so bottles of fresh DOT3 and then remove that sticker once it's flushed.

« Last Edit: June 16, 2019, 05:42:23 PM by MIPS »

Offline AMC of Houston

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Re: Mixed Brake Fluids
« Reply #3 on: June 16, 2019, 05:59:43 PM »
Maybe some shyster oil change place conned a previous owner into a high-dollar "Brake Fluid Flush" and added the sticker!
George G.
'81 Eagle Sundancer
'85 Eagle Waggie
1960 1902 Rambler Replica
'64 American
'70 AMX (Big Bad Blue), '70 AMX (White)
'77 Gremlin
'78 Pacer Coupe, '78 Pacer Wagon
'79 Pacer Wagon
'73 Jensen Interceptor
'86 Audi 5000 Turbo
'98 Aston Martin DB7
'09 Nissan Titan
'10 Nissan Maxima

Online MIPS

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Re: Mixed Brake Fluids
« Reply #4 on: June 16, 2019, 07:04:49 PM »
I noticed. A tiny bottle of DOT5 was $25, as opposed to a 1 ounce bottle of DOT3 which was $8 at LORDCO.
Well it's out of there now. Pumped the reservoir empty and wiped it down, then added fresh DOT3 and bled the fluid from each wheel until it ran clear. Found some sediment. Found a lotta brown fluid so we were probably in need of a replacement for a while now anyways. It might take until later tonight for everything to separate out in the container to see what's going on.
« Last Edit: June 16, 2019, 07:15:13 PM by MIPS »

Offline eaglefreek

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Re: Mixed Brake Fluids
« Reply #5 on: June 27, 2019, 07:22:19 PM »
The only benefit to DOT 5 is that it won't damage paint. I don't know why someone would go to the trouble of installing it in an Eagle.
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