blackbomber Posted August 31, 2014 Report Share Posted August 31, 2014 hey everybody, well I have a 84 king cab I bought new in 84 when I was 19 years old. now I am 49...everybody is telling to scrap it, and get something else, but what can I say, I just can,t do it....................so here is the deal.. even after a short trip like 2 miles, i can't touch the brake rotors they are hot.....So my shop says it's the wheel bearings...... not the brakes hanging up. but i had another mechanic look at it and he thinks it's the brakes.. so ,is there any way i can diagnose it my self????????? The bearings where repacked not too many miles ago, maybe 50'000 or less.....and i just recently drove the truck to santa fe, 900 miles round trip.... thanks for your help...... Quote Link to comment
datzenmike Posted August 31, 2014 Report Share Posted August 31, 2014 Sounds like the pressure is not fully released when you let off the brake. This can happen when the master can't return fully to it's rest position. Push down on the brake peddle with your thumb. There should be about 1/16" of free travel before there is stronger resistance. Does it have this play? Quote Link to comment
MikeRL411 Posted August 31, 2014 Report Share Posted August 31, 2014 One post is enough! Quote Link to comment
datzenmike Posted August 31, 2014 Report Share Posted August 31, 2014 Yeah I got rid of it Quote Link to comment
flatcat19 Posted August 31, 2014 Report Share Posted August 31, 2014 What about the slide pins being seized stuck? Quote Link to comment
tr8er Posted August 31, 2014 Report Share Posted August 31, 2014 I could be making a dumb suggestion because several factors could create variance such as air flow, but what about shooting the caliper body and hub area with a laser thermometer? Just to try to find the hottest spot. Just a thought. Tough to diagnose really. Better than taking off the front calipers and driving around for a while... Quote Link to comment
blackbomber Posted August 31, 2014 Author Report Share Posted August 31, 2014 shop said brake calipers were ok, pins ok..have to assume bearings at this point....Haynes manual doesn't jive with factory manual....one shows inner and outer bearing on outside of knuckle[factory manual]....Haynes shows one bearing on other side of knuckle..... any help here.....ps ...original wheel bearings on the truck... Quote Link to comment
datzenmike Posted August 31, 2014 Report Share Posted August 31, 2014 Wheel bearings that hot would be dry and screaming. Forget the bearings Um... brakes do get too hot to touch.... but not in 2 miles of non use driving. If you raise the wheel can you spin the tire by hand? hot... or cold.? I had a Sundance caliper 'seize' on me. The smell was like a burning clutch. Threw snow on the rim to cool it down. It steamed!!! Got wheel off and used a lug wrench to pry the pad against the piston to retract it. Pumped the brake pad back against the rotor and drove off... it was fine. Can see both doing this at the same time. It would seem like there is residual pressure trapped in the front line. Quote Link to comment
blackbomber Posted September 1, 2014 Author Report Share Posted September 1, 2014 I think you are right datzenmike....I am giving up on the wheel bearing theory...my shop was off....I took one of the wheels off...a lot of resistance to turn the hub...... also, .....I did the brake pedal test, and there is a little play before it gets stiff, but not much, maybe half of a inch... that was one of the things my shop mentioned was how stiff the brake pedal was.. but they said calipers were working fine.... okay masters!!!!! what is my next move.. also trying to find a new mechanic who works on his own, out of his house.....you guys are great, thanks for your help....30years and still running strong..passed emission test on first try last year.... Quote Link to comment
datzenmike Posted September 1, 2014 Report Share Posted September 1, 2014 If pressure is trapped. you could loosen a bleeder on one of the front calipers slowly. If fluid spurts out, close it and try spinning the wheel again. If it now spins normally then it can only be the master cylinder. Quote Link to comment
blackbomber Posted September 1, 2014 Author Report Share Posted September 1, 2014 thanks bud... I di try to open a bleeder..it just leeked fluid around the threads, but nothing came out the tip.... maybe I didn't open it enough..should I try again????? unscrew it farther?? Quote Link to comment
datzenmike Posted September 1, 2014 Report Share Posted September 1, 2014 Sure. Then check if the wheel is looser. Quote Link to comment
blackbomber Posted September 2, 2014 Author Report Share Posted September 2, 2014 didn't get back to the truck today...went fishin.. gotta go back to work tomorrow...work is going to be crazy busy this week .....I think this weekend will be my next chance to get back to the truck... but I will get back on that bleeder test when I can.... thanks so much for your help this weekend..you save me from tearing the hubs apart... I really appreciate it...... one of the happiest days of my life was when I drove this truck out of the dealership building...they had to move some cars and open the big double doors, so I could drive it outside.. it was top of the line,,had all the options........11,500 was the sticker price.....talk to you soon bud, thanks.. Quote Link to comment
blackbomber Posted September 3, 2014 Author Report Share Posted September 3, 2014 hey datzenmike. well I think I jumped the gun on the truck.. a friend came over and since I had her here I decided to bleed the front brakes...I didn't notice a lot of pressure when I opened them, but I had a clear tube on it, so we did three cycles on each side. she said the pedal went all the way down on each bleed.. I didn't notice a lot of air bubbles..fluid looked solid....after the bleeds , pedal seemed about the same stiffness as before....so I took off on a 2 mile drive... drove one mile , braked, turned around, then back too the house..... hub not very warm ,,,but unable to leave finger on the brake rotor, too hot to touch..both rotors same amount of heat........sorry I wasn't patient in my procedure,,,,any guess???master???? calipers or master cylinder.... Quote Link to comment
Parkinglotslider521 Posted September 3, 2014 Report Share Posted September 3, 2014 Another thing to check would be the soft rubber hoses. I have seen them disintegrate internally and let pressure flow one way but not another. Check master cylinder adjustment like mike said. If thats not the problem then pop the calipers off and see if you can compress them easily. If you can't then open the bleeder valve and try to compress them again. If you are able to compress them easily with the bleeder open, then look at the hoses and proportioning valve. If you are unable to compress them even with the bleeder open, the calipers are done. Quote Link to comment
datzenmike Posted September 3, 2014 Report Share Posted September 3, 2014 I doubt there was air in the lines but fresh fluid is still ok. These things get hot normally just from normal driving. The fronts do way more of the braking than the rears and on an all disc brake vehicles the fronts are always larger. I've checked the temp of my front brake before by sticking my finger through the slot and got a painful surprise. What a brake does is reduce forward kinetic energy motion on a 3,400 pound vehicle by converting it into heat. Raise the wheels and try spinning them. Are they still tight? Quote Link to comment
flatcat19 Posted September 3, 2014 Report Share Posted September 3, 2014 Piston push rod adjustment if you're not finding anything else wrong. Turn the rod tiny, TINY amounts then check to see if caliper let loose if tight. Quote Link to comment
dr.feltersnatch Posted September 3, 2014 Report Share Posted September 3, 2014 How old is the brake fluid? I have heard of brake fluid collecting water and heat turns it to steam causing a constant pressure in the system until it cools down. If its real old try changing your fluid Quote Link to comment
blackbomber Posted September 4, 2014 Author Report Share Posted September 4, 2014 thanks guys,,get back to it when I can.... buy I yhink we are on the right track now.. brake system. both Haynes and factory manual say look at output rod adjustment in the brake booster next....too tired to think right now...remember when jap trucks were built in japan....what a concept.... Quote Link to comment
datzenmike Posted September 4, 2014 Report Share Posted September 4, 2014 How old is the brake fluid? I have heard of brake fluid collecting water and heat turns it to steam causing a constant pressure in the system until it cools down. If its real old try changing your fluid I would think that when the brake peddle is released any pressure (hydraulic or steam) awould simply push fluid back into the reservoir until it reached zero. This is how the hydraulic pressure is released when you let off the brakes. The master end is open Quote Link to comment
banzai510(hainz) Posted September 4, 2014 Report Share Posted September 4, 2014 MY kinda new brake master it would slowly pump up. on all the brakes. I would have to realse a bleed screw. to get the pressure down. would take days to build up or just going down the street every time i pushed the brake. Got new master was fixed. if discbarke up from maybe buy another caliper. On my Cherokee I just swapped pads and then one would get hot. I just bought a new caliper and was good afyter that. Piston gets stuck Quote Link to comment
blackbomber Posted September 5, 2014 Author Report Share Posted September 5, 2014 thanks Datsun masters..good news I think I am onto something... I loosened the master from the brake booster,like really loose, barely finger tight. then took it for my usual 2 mile trip down the street...significant decrease in rotor heat... so maybe I can do that output rod adjustment and call it good for now...if I don't work Saturday....can you guys give me a play by play on that adjustment ..do I have to take the brake lines off to get the master out of the way, and how much flex are in those brake lines,,,,also, is it just one nut holding that rod in place......... thanks guys..... very tired ,new job and all........I should make Datsun commercials instead..... Quote Link to comment
flatcat19 Posted September 5, 2014 Report Share Posted September 5, 2014 Piston push rod adjustment if you're not finding anything else wrong. Turn the rod tiny, TINY amounts then check to see if caliper let loose if tight. can you guys give me a play by play on that adjustment ..do I have to take the brake lines off to get the master out of the way, and how much flex are in those brake lines,,,,also, is it just one nut holding that rod in place........ It is one nut tightened against a clevis that has a pin to hold the brake pedal. Mark the rod so you know where you started. Loosen nut. Barely turn. Test feel. Rinse and repeat. Cool part-you can drive a mile down the road, get out for feel, re-adjust, drive the mile back home. Quote Link to comment
blackbomber Posted September 6, 2014 Author Report Share Posted September 6, 2014 ok guys, do I have to unhook the brake lines to get the master out of the way??? I want to back off the output rod..also ,should I use dot 3 or dot 4 or does it matter..... also ,was gonna check the check valve any thoughts??? Quote Link to comment
datzenmike Posted September 6, 2014 Report Share Posted September 6, 2014 hey everybody, well I have a 84 king cab I bought new in 84 when I was 19 years old. now I am 49...everybody is telling to scrap it, and get something else, but what can I say, I just can,t do it....................so here is the deal.. even after a short trip like 2 miles, i can't touch the brake rotors they are hot.....So my shop says it's the wheel bearings...... not the brakes hanging up. but i had another mechanic look at it and he thinks it's the brakes.. so ,is there any way i can diagnose it my self????????? The bearings where repacked not too many miles ago, maybe 50'000 or less.....and i just recently drove the truck to santa fe, 900 miles round trip.... thanks for your help...... Meant to ask... have you replaced the master recently or worse have you rebuilt it or had the lines disconnected??? Quote Link to comment
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