Break grab

[grtescpa]

My front brakes grab when I first start out from a cold start. It does it more on a damp morning. After a few miles of use everything is normal. I have changed the pads and bleed the system twice. Still does it. Any clues??

 

[HoleshotHolset]

Moisture on either brake pads (front) or especially brake shoes (rear) will cause 'em to lock up unexpectedly. That's why having a bad axle/hub seal is BAD news... . been there, done that, got the T-shirt.



Matt

 

[ageorge]

I agree with Holeshot, if the rear shoes especially are damp they will lock with minor pedal pressure. If the rear seals are depositing any EP90 on the shoes it will be very touchy.

 

[grtescpa]

Originally posted by ageorge

I agree with Holeshot, if the rear shoes especially are damp they will lock with minor pedal pressure. If the rear seals are depositing any EP90 on the shoes it will be very touchy.

Thanks Guys for the speedy reply. I looked at the seals

front and rear. No leaks. Its only the front which grab. Its never done this befor and There is about 40,000 miles on the front calipers. I did find some water in the the fluid befor I bleed the system. Do you think a rusty caliper cylinder??

 

[ageorge]

I have 78,000 miles on my 98, and have changed out the fluid once@ about 50,000. Don't know what you mean when you say you found water in the fluid. The fluid is very much like a sponge : it sucks up water and absorbs it into the brake fluid if the system is either left open or has a way for air to be introduced in the system. you have to be very careful how long the cover is off the master cyl. , cover it up as quick as you can.

 

[DieselTim]

DOT 5

Have any of you tryed using Dot 5 brake fluid. It is silicone based and will not absorb water. It is purple in color, and will make your seal, rubber parts of the brake and clutch sys last much longer. No more rust or water in the system to worry about and the system can be run harder/ hotter temp. ( like braking under heavy loads) with less fade.

 

[Eric_77]

DOT5 is very BAD for our trucks. System is designed for DOT3,4. The seals are diffeent between these petroleun based and silicone based brake fluids. The new DOT5. 1 is compatible with DOT3 or 4. The DOT5 is only used as far as I know in Harleys and in Corvettes maybe Vipers. Some of the Euoprean high performance cars were also going to it but unsure if/when they did.



The DOT5 will cause rubber seals to lose elasticty and leak/fail.

 

[Joe]

Extended warranty is a good thing

My brakes had similiar sympton of pulling the truck to one side. On gravel lot, I noticed that one rear brake would lock up (even with ABS!) just before coming to a complete stop. Also, I would notice that the rear would be frozen after dipping the drums in water (boat launch). From previous posts I was pretty sure it was a leaking axle seal (have Dana Splicer 70 w/ LS). Dropped off the truck this morning at the dealer and informed that axle lube has contaminated the rear drums and shoes. New OEM shoes cost $250!!! Thank you for the 7 yr / 100K extended warranty that covers axle seals . That extended warranty has paid for a new $2500 transmission at 45K and now a $700 brake job at 65K. Still 9 month to go and 35K on the warranty



Joe



95 4x4 LWB AT

 

[grtescpa]

Originally posted by ageorge

I have 78,000 miles on my 98, and have changed out the fluid once@ about 50,000. Don't know what you mean when you say you found water in the fluid. The fluid is very much like a sponge : it sucks up water and absorbs it into the brake fluid if the system is either left open or has a way for air to be introduced in the system. you have to be very careful how long the cover is off the master cyl. , cover it up as quick as you can.

Water entered my system from an improperly replaced master cylinder cover. (thanks to my local NYS inspection station) I did not pick up on this till many miles and rain days later. I still don't know what is causeing this front grab. Still under warranty but I hate having to bring in to don't give a damm mechanics at Dealers.

 

[Missouri Mule]

Did you notice if you had brake fluid on your rotors? Almost any fluid will make them grab.

Never had water make brakes grab, usually had to ride brake after going thru large puddle to dry them out so they would be there when I needed to stop ( if you don't ride them a little when you step on brake to stop feels like you don't have brakes/as matter of fact you have very little breaking power).



Brake hoses could be collasping keeping pressure against front brakes, until they been used a few times. ( I know brakes hoses can cause calipers to stick but not certain when they do it, little use/ lot of use).

 

[sam peterson]

there seems to be an opinion that Dot 5 fluid doesn"t create moisture in the braking system---wrong---the moisture is still there and doesn't mix with the fluid--it just lays in droplets in the bottom of the cylinders---high altitude is not a good candidate for dot 5 either---Sam

 

[MikeR]

Both my old '99 and my '00 have always done this since new. The trucks don't sit for days either... I drive them everyday. When I get in the truck and start it after it's been sitting 8+ hours,the first time I step on the brakes they grab and feel like they almost lock. It does it everyday,and it's doesen't matter wether is rainy or 80 degrees out. I have a hard time believeing the moisture idea because it does it on sunny days too. They only do it that one time,then they're fine until the next cold start. Neither truck had any brake pull and none of my seals are leaking. I'd sure like to know why it does it.



PS. My wifes '95 with the old vacuum brake system doesn't do at all.



-Mike

 

[JGK]

Diff. fluid on brakes shoes

Joe,



FWIW, when I had my left rear seal replaced about a month ago, the whole inside of the drum was covered in fluid. The dealer just cleaned it all off with brake cleaner. The brakes work just fine. Tomorrow, it goes in for the right side seal - I expect the same thing will be done there (both done under the extended warranty also!). In your case, a nice way to get new brakes, but it may not be necessary.

 

[grtescpa]

Originally posted by Missouri Mule

Did you notice if you had brake fluid on your rotors? Almost any fluid will make them grab.

Never had water make brakes grab, usually had to ride brake after going thru large puddle to dry them out so they would be there when I needed to stop ( if you don't ride them a little when you step on brake to stop feels like you don't have brakes/as matter of fact you have very little breaking power).



Brake hoses could be collasping keeping pressure against front brakes, until they been used a few times. ( I know brakes hoses can cause calipers to stick but not certain when they do it, little use/ lot of use).

Nope. No brake fluid on the rotors. They are clean. Just read that someone else has the same problem. On a dry day. Mine still grab on a dry day but its worse on a damp morning. Could be the wet road making the skid easier. Thanks everyone for adding there comments on this problem.

 

[WCrovo]

Sam is correct. Grabby brakes on the first start with alot of dampness is OK esp. on the earlier single piston systems. If everything is the same and the grabbyness is new you have a problem and should let a good tech resolve it.