Losing brake fluid
Thread Starter
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Senior User
Joined: Mar 2014
Posts: 434
Likes: 2
From: Santa Cruz Mountains
Losing brake fluid
85 F350 Crew Cab 460, manual trans, 2wd SRW
Having to fill up reservoir every couple days..
Very moist around master itself. No drips.
Parts guy says it might be evaporating from the reservoir cap if its got corrosion and not seating well. The master does have some corrosion, but nothing beyond minimal and the cap retaining clip is snug. The cap doesn’t move when clipped down.
Have loosened and retightend the lines coming out of master. But it sure is moist around that thing. No obvious cracks in the master.
Bleeder valves are dry on all four.
All brake line connections are dry.
The brake light is on ALL the time.
Any other ideas? ...before we pull the rear wheels to check the cylinders?
Having to fill up reservoir every couple days..
Very moist around master itself. No drips.
Parts guy says it might be evaporating from the reservoir cap if its got corrosion and not seating well. The master does have some corrosion, but nothing beyond minimal and the cap retaining clip is snug. The cap doesn’t move when clipped down.
Have loosened and retightend the lines coming out of master. But it sure is moist around that thing. No obvious cracks in the master.
Bleeder valves are dry on all four.
All brake line connections are dry.
The brake light is on ALL the time.
Any other ideas? ...before we pull the rear wheels to check the cylinders?
Tuned
Joined: May 2013
Posts: 396
Likes: 5
From: Ottawa, Canada
The lids are notorious for leaking. I've been through a few master cylinders and all mine leaked a little. My brakes work fine, I haven't found any leaks and I have to top it up every 2 or 3 weeks.
Follow the lines and see if any are wet.
Does the brake light go off if you lift the e-brake pedal? My 85 blew a wheel cylinder years ago, the "safety valve" kicked in blocking the rear brake lines and diverting the brake pressure to the front (to my understanding anyway). It also took a lot of pedal to stop the truck. If you can't find any leaks pull the drums and look for a wheel cylinder leaking.
Follow the lines and see if any are wet.
Does the brake light go off if you lift the e-brake pedal? My 85 blew a wheel cylinder years ago, the "safety valve" kicked in blocking the rear brake lines and diverting the brake pressure to the front (to my understanding anyway). It also took a lot of pedal to stop the truck. If you can't find any leaks pull the drums and look for a wheel cylinder leaking.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Pull the master cylinder and check the brake booster it my be full of brake fluid. Not an uncommon thing to happen. If the master has sealed itself to the booster and the seal on the brake rod has gone bad the booster can suck fluid out of the master cylinder past it's seals right in to the brake booster. If brake fluid is disappearing with no apparent leaks any where chances are 90% it is going in to the brake booster.
Lead Driver
Joined: Nov 2013
Posts: 7,174
Likes: 1,174
Having to fill up reservoir every couple days..
Very moist around master itself. No drips.
Parts guy says it might be evaporating from the reservoir cap if its got corrosion and not seating well. The master does have some corrosion, but nothing beyond minimal and the cap retaining clip is snug. The cap doesn’t move when clipped down.
Very moist around master itself. No drips.
Parts guy says it might be evaporating from the reservoir cap if its got corrosion and not seating well. The master does have some corrosion, but nothing beyond minimal and the cap retaining clip is snug. The cap doesn’t move when clipped down.
Also, I didn't see any mention of replacing the gasket for the cap. My MC was wet on the outside, just as you described. A new cap and gasket took care of it.
Thread Starter
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Senior User
Joined: Mar 2014
Posts: 434
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From: Santa Cruz Mountains
Replaced master cylinder... brakes are back.
Was not able to see inside booster to clean up any fluid. Barely enough space for rod.
Parts guy said there is a weep hole and we like very much that all fluid leaking from master
in the past month (almost 2 quarts) is weeped out and not infected booster gasket as
it runs 120$!.
Brake light is still on. Maybe kicked the emergency brake. It doesn’t operate at the moment. Any guidance as to repair it? Parting out an 83 f250 so have those parts if
they will fit... ?
Also, is it protocol to start a new thread for the emergency brake question?
Was not able to see inside booster to clean up any fluid. Barely enough space for rod.
Parts guy said there is a weep hole and we like very much that all fluid leaking from master
in the past month (almost 2 quarts) is weeped out and not infected booster gasket as
it runs 120$!.
Brake light is still on. Maybe kicked the emergency brake. It doesn’t operate at the moment. Any guidance as to repair it? Parting out an 83 f250 so have those parts if
they will fit... ?
Also, is it protocol to start a new thread for the emergency brake question?
Tuned
Joined: May 2013
Posts: 396
Likes: 5
From: Ottawa, Canada
The ebrake pedal needs to be at the top to turn the light off. The only other thing I'm aware of that can trip it is the "safety valve" that blocks either the front or back brakes when they blow. But I think that only comes on when you try to apply the brakes.
For the ebrake not working does the pedal go down or is it just weak?
For the ebrake not working does the pedal go down or is it just weak?
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Thread Starter
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Senior User
Joined: Mar 2014
Posts: 434
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From: Santa Cruz Mountains
The brake light was not always on before loosing fluid started.
The e brake is cocked out to right a bit so we haven’t even tried using it as we have been
working on other things and didn’t want to create a problem by trying it. Have 2 trucks to tow tomorrow, otherwise we go try right now. So we have copilot hold brakes while we load
the trailer.
It is coming up on priority list of repairs and we have the f250 as parts to salvage if they work on f350s. ?
The e brake is cocked out to right a bit so we haven’t even tried using it as we have been
working on other things and didn’t want to create a problem by trying it. Have 2 trucks to tow tomorrow, otherwise we go try right now. So we have copilot hold brakes while we load
the trailer.
It is coming up on priority list of repairs and we have the f250 as parts to salvage if they work on f350s. ?
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FTE Legend
Joined: Nov 2015
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From: Angier, NC
I would this way if you or someone else does a search for ebrake it will show up as its own post and not in the middle of something started for say xxxx?
As for a weep hole in the booster I have never seen one in any of the ones I have played with. I have heard of the booster filling all the way up to the vacuum hose and the motor pulling it in and the person wondering why the motor is smoking when the motor checks out good.
You can pull the vacuum hose & check valve off the booster, put a small hose down inside and see if you can suck any thing out.
Dave ----
As for a weep hole in the booster I have never seen one in any of the ones I have played with. I have heard of the booster filling all the way up to the vacuum hose and the motor pulling it in and the person wondering why the motor is smoking when the motor checks out good.
You can pull the vacuum hose & check valve off the booster, put a small hose down inside and see if you can suck any thing out.
Dave ----
4wd Low
Joined: Jul 2017
Posts: 14
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I replaced my master a couple of years back and had brake fluid all over for a couple of months. I finally took 3000 grit sandpaper and smoothed the mating surface on the master cylinder out. I syphoned all the fluid out and took extreme care to make sure no filings would fall into it. Solved the problem. Even a tiny imperfection in that mating surface will lead to leaks.
By the way, when the master went out in the first place, nothing can replicate the excitement of calmly compressioning down a mountain in the Wyoming Rockies, with an Alaskan Camper, fully loaded from a two week camping trip with your wife and dog in the cab, really needing to slow down for the corner that's coming, and the brake going to the floor. It's major wake up time! Luckily I was able to pump them back up.
By the way, when the master went out in the first place, nothing can replicate the excitement of calmly compressioning down a mountain in the Wyoming Rockies, with an Alaskan Camper, fully loaded from a two week camping trip with your wife and dog in the cab, really needing to slow down for the corner that's coming, and the brake going to the floor. It's major wake up time! Luckily I was able to pump them back up.
Thread Starter
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Senior User
Joined: Mar 2014
Posts: 434
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From: Santa Cruz Mountains
Pulled booster vacuum line out and grommet to insert 1/4 inch hose into booster.
Attached 1/4 inch hose to 1/2 inch hose and sucked... then spit out some nasty brake fluid!
After a few more times of the same result we attached 3 feet of 1/2 inch to the 1 foot of
1/4 inch and were able to pull fluid out without the nasty stuff reaching our mouth. Filled a coke bottle full.
It’s still not even close to the quart and a half we put in over the last month. If it did get sucked into
the engine does that mean it burned up and out the exhaust or into oil pan? Is it best to change the oil?
We did notice some smoky exhaust every so often last week. Short cloudy white smoke episodes every now and again. Usually at a stop light. Does it get into the oil pan though?
Will try taking the proportion valve wire off in the morning.
Attached 1/4 inch hose to 1/2 inch hose and sucked... then spit out some nasty brake fluid!
After a few more times of the same result we attached 3 feet of 1/2 inch to the 1 foot of
1/4 inch and were able to pull fluid out without the nasty stuff reaching our mouth. Filled a coke bottle full.
It’s still not even close to the quart and a half we put in over the last month. If it did get sucked into
the engine does that mean it burned up and out the exhaust or into oil pan? Is it best to change the oil?
We did notice some smoky exhaust every so often last week. Short cloudy white smoke episodes every now and again. Usually at a stop light. Does it get into the oil pan though?
Will try taking the proportion valve wire off in the morning.
FTE Legend
Joined: Nov 2015
Posts: 30,912
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From: Angier, NC
When it gets ducked into the motor it just burns it and out the tail pipe sp I would not worry.
I would worry a little of the brake fluid in booster what it may have done to the rubber diaphragm?
Guess you could spray brake clean in and suck it out then pump air it to dry the brake clean.
Or it could last for ever and not be an issue.
Dave - - - -
I would worry a little of the brake fluid in booster what it may have done to the rubber diaphragm?
Guess you could spray brake clean in and suck it out then pump air it to dry the brake clean.
Or it could last for ever and not be an issue.
Dave - - - -