funky wet/humid brake issue
 

Ok guys, on the road again in this beast and have a couple issues I would like some help on. first is the brakes. They work awesome when it is dry out but during a thunderstorm the other night and once when it was just really humid, they just didn't want to stop the van....I was standing on the pedal and nothing (poor little rice burner in front of me off the exit ramp probably messed himself). The second time it wasn't even wet, just really humid...then the third time last night when it was raining lightly....I'm thinking maybe some air in the lines or well....maybe looking at the brakes duh...but gimme you input, I haven't done any brake troubleshooting on big vehicles just bikes and quads, any help is awesome.

Second issue is a wobble vibration that is seeming to get worse, I'm thinking a u-joint going (can't go above 65 right now) and I only have about 400 pounds of freight in her.

Third is what I think might be the power steering pump. I'm getting a grrrrrrr---rrrrr sound coming from up there and I've been having some clunking up front (a friend changed out the ball joints, said they were original and popped right out, he thought that was making the clunking but it seems he was wrong...again, that might go back to u-joints) Anyway thanks for the help guys, sorry the search isn't working on my phone

For the braking issue I think I would be looking towards the vacuum pump or pump drive belt. The sound you hear could be connected, maybe bad pump or other accessory or idler pulley going bad.
The vibration could well be a universal joint or a bad carrier bearing (if it has one). Easy to check, parking brake on, trans in NEUTRAL, get under and check for play in the joints.
Clunking could be a bad sway bar drop link bushing, bad shock bushing.

If the vans have the twin i beams check the radius arm bushings, the vibration could be a u-joint, check the yokes and make sure the cross is sitting in there true. My 84 has the joints held on by u bolts and the tabs that center the joint on the yoke are noted to were and allow the joint to drift out of center. The brakes, check your wheel seals, look on the backing plates for any signs of oil leaking from the axle. I have also heard about organtic brake shoes acting wierd in wet cold or humid weather

Change the brake pads to metallic brake pads, the organic ones soak up water and take forever to dry out when your driving. As for the power steering noise, these trucks and vans all had the same powersteering pump. Its the same as on the F-150/250/350/Bronco. Is it a whiney grrr...or a screech when your turning all the way to the left or right?

It is a whiney grrr on the power steering....didn't notice tell recently (haven't driven it for a few months) and had all the belts changed.

The driveshaft had play in the u-joints and the slip yolk for some reason. Took em off, but they all look good. I changed the rear one, just checked the front one. all dust boots are good, all needles are there and there is plenty of grease in them. I'm a bit concerned about the slip yolk play.

I'm gonna have the shop check the tires (I had some used ones put on) belt might be broken I guess?

err...sucks working on this in the rain!

Don't have a clue about the brakes, thats just weird. In wet weather, my brakes will lock up quick if they are wet. After two or three stops they warm up and dry out.

Check the power steering fluid. When the fluid is low they often make noise.

Looking like the vacuum pump! noise is covered with that, the brakes and the intermettant loss of cruise control.

The clunking is still getting to me, as is the vibration. I checked the steering and all I can find is if I rotate the steering linkage forward or back, it does clunk and the lube joints are oozing when I lubed it. The noise seems to be the vacuum pump, explains the brake issue too and some other odd things lately.

So, after doing some research (and leaving out the hard pedal w/o brakes....sorry guys, important clue there) It has come down to vacuum pump, vacuum lines, brake booster, or check valve. Pump is pulling 18 so that's good (unless it is just starting to go, if that is a possibility)....checking the check valve and booster next

Well the pump may make 18in BUT IIRC there is something to be said about recovery time, i think it has to pull that 18in in like 15sec. the ceck valve in the booster can be checked by pulling the line at the booster you should here a woosh. I had some odd booster issues with my truck to where i would get one good ress of the brake and in about 6sec the pedal would come back up as if the vac pump quit working, but the vac pump pulled 26in fast and replacing the booster fixed it.
Oh and as far as the clunk check your radius arm bushings, they are the arms that run from the I-beams to the frame

So, I pulled the check valve and air flows very good in the direction to the pump...but, it sounds like a kazoo, for a second if you blow back toward the booster, This wouldn't explain the cruise though....or would it? Is there a way to test if the vacuum system leaks?

Start up was good, pulled 19 actually (tighter fitting for the tester) right away...very quickly? Revved it up, to about 2000 rpm pulling 26 on the vacuum gauge, let off, dropped back down to 19 and held steady. turned it off, steady drop to 0 in about 5 seconds???/