87 345 Brake Issue

[John P]

I Drove 7 miles to a local car show doing 35 mph with no issues. While driving 3 mph on the strip the MH started pulling to the left and it felt like a tire going flat. I pulled over, checked the tires, all were fine. I returned home noting that the issue went away when driving 35 mph. The next day it did the exact same thing but instead of returning home I drove an additional mile doing 3 mph when the LF brake started smoking. While pulling over the brake peddle went to the floor and took a couple pumps to stop. The dash brake light came on but went away after pumping. The LF brake was screaming hot and fluid had overflowed from the brake fluid canister. I let it cool for an hour then drove it home and everything worked normal. Master cylinder? Poor vacuum? Brake canister? Any thoughts will be appreciated.

[ROBERT CROSS]

Sounds like the caliper piston or wheel cylinder may have seized, boiling the moisture in the fluid.

POI...brake fluid should be changed on a regular basis. I do it on the Burb every 2 yrs. Brake fluid is a notorious moisture absorber...that is what boiled away.

Bob
🇺🇸

[GCinSC2]

What Bob pointed too and I'll add as an it's in the reference library but I've never experienced it. Hydraulic hose internal failure creating a flap like check valve holding pressure.

[cmadmaxman]

I have had the bad brake line causing lockup, but not on the stream.

I did have an issue with the spacing between the hydro boost and master cylinder though. This setup is very finicky about proper spacing. When replaced my master cylinder, I had to put a .030 shim between the two. The master has to release the line pressure or it will lock up the brakes. You didn't mention replacing the master, but this happened to me!
All was fine for a portion of the trip, then at the end started locking up!

[Boom Sounds]

I no expert on this and I'm sure there are several potential causes. I've had the inside of the hose collapse issue on my 250. I would replace both if they haven't been done. Always do that stuff in pairs. It's relatively straightforward and dirt cheap. You can rule out that cause and also be safe in the knowledge that the hoses should be good for another ten years.

Have a look at this, which might give you some more pointers.

[bkahler]

The rubber hose from the frame to the caliper is probably collapsed inside. This is a common occurrence with older rubber brake lines.

What happens is when you push the pedal you force brake fluid past the collapsed brake hose and when you let up on the brake pedal the pressure does release at the caliper which causes it to act as if you were still pushing the brake pedal.

[ddhisself]

GM trucks from that era were NOTORIOUS for collapsing front (and rear) brake hoses. My recommendation would be to replace ALL rubber brake hoses, and rebuild or replace both front brake calipers. (And make sure you use steel caliper pistons, not phenolic.)

[JohnTF]

Typical caliper looking up .
You should replace in sets - these being the front , the set is the 2 front , does not mean rear .
Sets are on the same axial .
One of the best pricing is RockAuto , but if you are not familiar looking up parts , it may be hard to be sure of correct parts , return shipping can eliminate savings , same with core returns - be sure to check shipping & parts total .
Shipping has gone high the last few yrs. , making it hard to find internet deals .
Using known quality brands - each brand will have 2-5 levels of grade [ kinda ] parts ,
so I always recommend an mid grade .

[PeterH-350LE]

Originally Posted by cmadmaxman

I have had the bad brake line causing lockup, but not on the stream.

I did have an issue with the spacing between the hydro boost and master cylinder though. This setup is very finicky about proper spacing. When replaced my master cylinder, I had to put a .030 shim between the two. The master has to release the line pressure or it will lock up the brakes. You didn't mention replacing the master, but this happened to me!
All was fine for a portion of the trip, then at the end started locking up!

I had to deal with this very issues myself on 1987 345, except it will lock up all 4 wheels and not just 1 (at least in my situation)
It is either caused by the wrong size pushrod or a small difference in the piston recess of the master cylinder.

[NOAZRK2690]

Stuck brake caliber. Replace.

[GCinSC2]

JohnP,

Any update?

Gary

[shepherd57]

Maybe there in not enough free play in the pedal linkage.
There should be an adjustment on the rod above the master cly that goes up to the brake pedal.
I had a similar problem and by adjusting that rod cured the problem.

[John P]

Thanks everybody. Great thoughts and ideas. I will replace both front calipers and both front brake hoses. I tried ordering these parts on line but found there’s several possibilities especially for a P30 motorhome My intent is to jack up the motorhome, remove the tires and wheels, take photos then order the parts. I will post the Final results when completed. Thanks again for the comments. Very helpful!

[Boom Sounds]

Originally Posted by John P

Thanks everybody. Great thoughts and ideas. I will replace both front calipers and both front brake hoses. I tried ordering these parts on line but found there’s several possibilities especially for a P30 motorhome My intent is to jack up the motorhome, remove the tires and wheels, take photos then order the parts. I will post the Final results when completed. Thanks again for the comments. Very helpful!

You should have the JB9 Motorhome brake set up, but as you say, casting or hose ref numbers are always best. Check your VIN into the AC Delco parts look up site which should help guide you. Cross ref with Dorman and RockAuto. You might want to get a full CompNine VIN report for your coach. It’s only a few bucks.

[Paul J Mauro]

Originally Posted by JohnTF

Typical caliper looking up .
You should replace in sets - these being the front , the set is the 2 front , does not mean rear .
Sets are on the same axial .
One of the best pricing is RockAuto , but if you are not familiar looking up parts , it may be hard to be sure of correct parts , return shipping can eliminate savings , same with core returns - be sure to check shipping & parts total .
Shipping has gone high the last few yrs. , making it hard to find internet deals .
Using known quality brands - each brand will have 2-5 levels of grade [ kinda ] parts ,
so I always recommend an mid grade .

just did this job on my 85 345 -getting harder to find calipers ,got mine from a local GM truck place but it took weeks to get them but hey its better than draggin the anchor

[Paul J Mauro]

compnine vin report good idea

[John P]

First of all I want to thank everybody that replied to my overheating front brake issue. I replaced both front calipers and both front brake lines. Everything works perfect now. The culprit was the brake hose. After dissecting the hose I found the restriction at the hanger bracket. The bracket evidently swells as it rusts to the point that it restricts brake fluid going back into the reservoir. It’s all fixed. Thanks again.

[John P]

4 pictures attached.

[PeterH-350LE]

Originally Posted by bkahler

The rubber hose from the frame to the caliper is probably collapsed inside. This is a common occurrence with older rubber brake lines.

What happens is when you push the pedal you force brake fluid past the collapsed brake hose and when you let up on the brake pedal the pressure does release at the caliper which causes it to act as if you were still pushing the brake pedal.

John, Thanks for following up on the cause and repair. And the grand prize goes to no other than bkahler.

[Air345Fly]

What are the shiny extensions on the wheel hub. Are they wheel
adapters?