Intermitent brake problem

[prototech]

In the morning when its really cold it seems like my brake booster doesn't want to work. when this happens I have to use both feet to get the truck to stop and the brake light and anti-lock light come on until I accelerate again. once the truck warms up everything seems to work fine. I replaced the check valve on the booster recently and that helped a little but it still happens on occasion. has any one had any problem like this and if so how did you fix it or what did you find? I hope my vaccum pump is not going out!

Proto

 

[paccool]

I never had the problem you are describing when my booster gave out but the brake and antilock light were coming on and I had trouble stopping when staying on the nbrake for a long time such as coming off the freeway to a stop light and then sitting there for a couple of minutes with the brake applied.



I replaced the booster as well as the master cylinder, that took care of the problem. You can see if the pump is working by disconnecting the main line at the booster and installing a vacume gauge. I did that and all was well. Then hooked up the booster and saw a drop. Pulled the check valve and plugged off and saw the vacume come back up. If you have cruise control, there is a line to that as well and if the diaphram is bad there could cause a drop in vacume as well.



Hope this helps.

 

[prototech]

thanks Stan,

I'll give that a shot as soon as the weather breaks.

Proto

 

[JLEONARD]

Proto,

I have a similar problem, but only when the temps are in the low single digits. I can actually hear a leak from inside the cab, but when I try to hear it from the engine compartment i can't becaue the engine is too loud.

I'm thinking it's a old stiff hose that won't clamp tight on one of the plastic fittings when everything contracts with the cold temps.

When the temps are a little warmer, everything works fine, or if I'm in a lot of city traffic and the engine compartment warms up it's fine.

Jay

 

[prototech]

all my hoses look like their in good shape, I'll have to look a little closer. This problem is really driving me insane, it seems to be worse when I haven't plugged in at night. As soon as I get a chance and some $$$$ I think I'll replace the booster just for S's& G's.

Thanks Jay!

Proto

 

[TKingsbury]

I'd be interested to see what is the cause, as my truck has done this too. It was only during the first pedal aplication and it went away. My steering also has no power assist when it's first started on a cold morning. I know one has nothing to do with the other, but I figure it must be a temperature related problem.

Travis. .

 

[Case500D]

My solution

Hi Fellas,



I had this problem on my W-250 a couple of years back. The old vacuum line was collapsing at very cold temperatures when the brake pedal was applied. The line also had a problem where it hooked into the check valve. It was making a 90* turn and was especially collapsing at that sharp bend. I replaced the old vacuum line with a section of fuel line and put a 90* plastic barbed elbow up by the check valve. It has been working fine for 2 years now. I think I use 1/4" braided fuel line, but measure before you buy anything. Hope this helps.



Jeremy

 

[prototech]

Hey Jeremy,

thanks for the info Ill have to look at that!

 

[prototech]

Hey guys,

Yesterday was a fair day, a little colder than I would have liked, but I got to work on my truck a bit. I changed out all the vaccum lines and bled the brakes, and I still had the brake and anti-lock lights come on and the brake pedal gets hard during my test drive last night. I checked the vaccum pressure it's at about 25 inches I would imagine that should be enough to do the job? only thing left is the brake booster, guess I'll try that next.

proto

 

[cdrider]

Prototech----------

I had the same problem you describe (hard pedal only when cold) on my 93 W250. I replaced the booster and that solved the problem. I used a rebuilt booster with a lifetime warranty, but I've had to replace the rebuilt boosters about every 10,000 miles-----a real PITA.

If i had it to do over I would look around for a NEW booster(same for master cylinder).



K

 

[prototech]

Originally posted by Case500D

Hi Fellas,



I had this problem on my W-250 a couple of years back. The old vacuum line was collapsing at very cold temperatures when the brake pedal was applied. The line also had a problem where it hooked into the check valve.



Jeremy

Hey Jeremy,

It turns out that my main 3/8 vacuum line was the problem after all! it was very soft and spongy down by where it hooks to the vacuum pump. I just created another leak when I replaced all of the vaccum lines. I broke off the fitting on the vacuum sensor that mounts to the fender and my quick fix leaked really bad when I checked it this morning. I found a better way to fix it and now all is well, brakes working good!!!

thanks again!

Proto

 

[Case500D]

Proto,



Glad your problem is solved.



Jeremy