This is a very wierd issue and I have almost diagnosed it? The car will drive normally, then in it will start to gain drag until it basically will not even move. It usually takes about 10 minutes for this to start happening. Sometimes you will begin to feel the drag and then it will just randomly stop dragging and drive normally. When it happens, the brakes will feel really hard. I felt it had to do with the brake booster, so I removed the vacuum that was going to the brake booster and continued driving which solved the problem for a bit, but as I kept driving the problem started again. This is a really wierd issue I had it diagnosed at the shop, all they did was a brake flush and it didn't solve the problem. Please help me out with this one
The car is a rhd 92 fd

 

I would drive it till it happens again and then pull over and feel the wheels.

If one is much hotter than the others, you at least will know which brake has the problem.

 

Alright, just got back from a drive and all four wheels are really hot, like I can't touch them HOT!

 

Sounds to me like something is forcing your master to apply pressure. I would start diagnostics there.

 

Also, if you allow it to sit for a few hours the issue goes away?

 

Theres a 1 way valve in the brake booster line (from UIM to master cylinder)

Replace it, then see if you still have the same issue.

 

Yeh its probally thecheck valve in the hose going to the brake booster. Mine went bad all of a sudden awhile ago. Problems solved.

 

Hmm, Ill try that and tell you how it goes. I removed the hose with the check valve on the top of the brake booster and it appeared to help for only about 5 minutes?

 

Ok, well look at it this way.

All 4 wheels are too hot to touch, this means ALL 4 brakes are stuck on.

I dont believe for a second that all 4 brakes on the car have all of a sudden stuck on for no reason (unless you've recently had a fluid change to an uncompatible fluid or some contamination has got into the brakes)

So yeah, the only way all 4 brakes would engage would be that the brakes are being applied all the time. Either your riding the brake pedal constantly, or boost going into the brake master cylinder is pushing the brakes on all the time (i.e broken 1 way valve)

FYI the idea of that valve is to provide vacuum so when you come off the brakes it sucks the fluid back into the resovior, retracting the brake pads (as far as i know anyway)

 

I have had this problem in 2 different motorcycles for 2 different reasons.
One was the filiter screens in the ABS pump pistons were plugged up not allowing fluid to return to the master cylinder. The front caliper would slowly build pressure until it just wouldnt go any more.
The other was a gummed up master cylinder. There is a rubber flapper in it that allows fluid to return and releases pressure in the brake. The holes that allow fluid to reach the flapper were plugged once again not allowing pressure to release.

Another possibility worth mentioning is to also check the lines. I have heard sometimes internal brake line damage can create a one-way flapper valve that will cause similar symptoms. I havent personally seen this failure, but you never know.

Whatever the cause, it sounds like brake fluid not being allowed to flow back into the master cylinder.

 

Alright, so either the return hose is clogged, or the check valve on the vacuum is clogged. Where do I find the check valve that goes to the master cylinder, does anyone have a diagram? Could I just clean the check valve, or do I have to replace it?

 

Replace the check valve, the internals are probably shot. It's been a while since I had my FD but I think theres a factory recall for the hose going to the booster. ie if it has a white dot on it, it has been replaced (but still may have gone bad again).

 

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This happened to me at school some hater put regular 10w 30 no much just a little and **** up my whole breaking system and had to replace every line every caliper and master cylinder. Yes all 4 wheels in my car would get stuck so bad that the car couldn’t move sometimes and if you let it sit it will be all better but only for a short drive. The way I found out was threw the dealer ship they drained all the brake fluid into a clear container and you could clearly see there was oil mixed in there. You should drain your fluid and take a good look.

 

They did a full brake flush at the shop. It was partially contaminated and then when they replaced it, the brakes worked good for the drive back, then the problem just got worse and worse.

 

Do you know what was in it? If there was oil in it draining it will not do anything by what the dealer ship told me since oil in the brake master cylinder will make anything in the system that is made of rubber will swell up like the O rings in the calipers, master cylinder and all rubber lines. By the looks of it they are right since draining your brake fluid didn’t help at all.

 

Yea, all it basically did was get rid of the issue for a day, then it came right back. I believe it is probably the check valve for the vacuum that releases the pressure, because sometimes it will just randomly go away. There must be some type of clog in it.

 

If the booster check valve was bad it would just make the brakes harder to apply, not cause your symptoms. You most likely have a clog some where in the hydraulics.
Since it seems to be all four wheels, it's probably in the master cylinder but it could be in the ABS or the proportioning valve. You can isolate the problem buy causing the problem, then see if you can release the pressure first at the m/c hard lines then back to the ABS etc..

Paul

 

^^^^

Yup, the check valve doesn't "release pressure", it prevents the motor from sucking it back out of the booster tank, and leaving you w/ no assist.