Oil in the brake fluid reservoir

A few years ago, about 3, my father accidentally put oil into the brake fluid reservoir of our GMC Acadia, we never did anything to fix it until recently when my father decided to take it into a shop to get it fixed, the situation turned out to be too much for them and instead just changed our tires. My father still drives this car for work and just claims that you have to press the pedal really far in to get some brake, and press it hard in twice for a hard brake. I am wondering if it’s possible to repair the brakes system to avoid this uncomfy workaround, or if the car is far gone and to abandon all hope. I was thinking of replacing the brake pads and calipers entirely but upon further thought I came to the conclusion that it probably wouldn’t be enough. Is there anything I can do that won’t break the bank?

Any competent independent shop can repair your brakes.
Do not drive the vehicle in this condition.

This is what Tom&Ray said about this:

Tom: Motor oils, including synthetic ones, are based on mineral oils. The problem is that mineral oils and rubber don’t mix well. The oils can cause rubber to swell or deform, and because there are lots of rubber seals in your brake system, that eventually can make your brakes stick, leak or even fail.

Ray: So the safest thing to do would be to replace every part of your brake system that uses rubber seals. That’s pretty much everything except the steel brake lines! So that’s going to run into big money.


I think you need another mechanic. Any competent mechanic can remedy this. It will be pricey but straightforward. All the rubber parts that are touched by brake fluid need to be replaced, master cylinder, wheel cylinders/calipers and the flexible hoses and a complete flush of the old brake fluid. I can’t wrap my head around how a shop would not do the work and consciously allow someone to leave with the brakes in such bad shape.


Biggest cost could be the ABS system. Find a good shop and get an estimate ASAP. It’s not safe to drive.


I’m more curious about what you’re going to tell the parents of the child he ran over between the first and second press of the pedal.

This car is dangerous to drive and needs to be taken off the road immediately.


Agree with ALL of the above. This is a fatality waiting to happen.

Calipers can be easily rebuilt with a $12 seal kit, master cylinder as well for a little more. The ABS modulator needs to be replaced. I don’t think there is a combination valve on this so that is good.

The system needs to be completely flushed with clean brake fluid before you start, again while it is all apart, and again when it goes together. It is a lot of work but not a ton of cost for a DIY job.


Lucky it’s even had any brakes for 3 years. At some point during a panic situation that brake pedal may decide to just slam into the floor.

Calipers, master cylinder, flush the brake lines, and maybe replacement of the ABS unit is the way I see it.

But, unless I missed something, we don’t even know how old this ignored-maintenance Acadia is.
It could be as old as 14 years, and if the engine and transmission have been as badly abused as the brake hydraulic system has been, it might not be a good financial proposition to spend the money for that work.

At some point, the bad brakes may be compensated for by the fact that the vehicle can no longer move under its own power.


One thing the OP did not say where they were at I sure hope they are not in my area


We left it sitting for a few years, so yeah, I’m gonna try to talk him into selling it for parts at the very least to get some coin. We don’t even need it as we each have a car already.

At any point after the motor oil was added, was the brake fluid even changed?

Tell your father he’s an irresponsible idiot. If he crashed into someone I cared about, I’d be suing him for every last dollar I could get, with a very good chance of winning that case.


If your irresponsible father still drives this car he’s a jerk. No other way to put it.


Had a neighbor, 2 broken tie rods I think, saw them hanging down, he was like it is fine if I don’t go over 35.

Dad doesn’t understand the damage cause by the engine oil in the brake reservoir so he must be insulted.


Which one ?


We have a 2001 Ford F-150 that we both drive, and a VW Jetta mostly for me and my brother, I hardly go out so it’s usually my dad driving the F-150 and by brother driving the Jetta. For some reason he uses the Acadia for his second job at the restaurant, he says its so our speaker system won’t get stolen

Keep your speaker system in your house, where it belongs, and it is less likely to be stolen.

my 2 cents.( not worth much) yes the car should be fixed or taken off the road. and yes the father is being irresponsible and some people need a swift kick in the butt to understand. but OPs father is not reading this. I dont think calling OPs dad a idiot or jerk is they way to go. how would you feel if people were calling you father that. I thought we were here to help and give advice.
ok, now you all can jump on me. LOL

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