Brakes

[troy]

Hoping someone can help out , my 109 brakes suck , it’s has a series 3 tower with power brakes , has new wheel cylinders / lines/master cyl/ brake booster . First brake application every morning the brakes work great , after that the pedal is hard and the brakes suck , if I’m on a hill stopped the truck will actually start creeping back and I can be pushing hard on the pedal and it still creeps . Today I pulled a front wheel off to make sure I have the brakes assembled correctly , I put a new master cyl on today , adjusted and bled the brakes again and it is the same as it was . The 2.5 diesel has a vacuum pump that the booster is attached to , the vacuum is good the booster is holding vacuum, I even took the new master cyl off and and depressed the pedal and the brake rod is not hanging up anywhere , I put the master cyl back on the booster studs and moved the pedal until the master cyl moved a little , it has some free play so the piston should be coming back . It is like the thing has manual brakes , anyone have any ideas ? I’m at a loss here . I find it weird that they work great first application , pedal is soft and it stops great . Troy

[terayon]

Hi Troy,

I'm not sure if this is your issue, BUT be careful how you adjust the brake pedal... I didn't realize I had mine out of alignment and I had (over the summer) worn the bore out of the cylinder. It leaked, lost pressure, etc...and I ended up replacing it.

I'll keep an eye on this tread as I'm keen to see how you over come this. My series brakes suck... but are not as bad as yours!

Jordan

Sent from my SM-N986W using Tapatalk

[troy]

Hi Jordan actually did some checking today , which I should of done first but oh well . I put a vacuum gauge on the vacuum pump to make sure the vanes were not stuck in the rotor ( the motor had been sitting for 10 years) it checked out good . So I pulled the pipe plug out of the booster and hooked up the vacuum gauge to it . I ran the truck and The thing has vacuum until I apply the brakes and then within 5 seconds there is no vacuum . The brake booster has a leak when I apply the brakes. The booster is barely a year old .

[troy]

So I know this might sound stupid and Iam hoping someone can answer this but when I was checking the vacuum the pump was putting out , it made a ton of vacuum , my gauge goes to 30 inches and the needle was pegged , it made me wonder if it’s too much vacuum and it is the reason the booster crapped out , I have power brakes on my 88 with a 2.5 n/a also but I used a defender pedal box and a type 50 booster , this has a series 3 pedal box and booster , I would think it shouldn’t matter but maybe the defender boosters were designed different to handle the vacuum the pump is putting out? I believe the 200 tdi and the 19j and 2.5 n/a have the same vacuum pumps , does anyone have a series booster and one of these engines in their rig ? I hope it’s just a faulty booster but I would feel better if someone told they are running the same deal without any issues lol

[terayon]

Hmm, sorry I can't comment about boosters... as I don't have a tonne of experience with them and I am still working on the rebuild of an old gerling remote booster... maybe it's time to find an expert. Do you follow Britannica Restorations on YouTube? Mike is a great guy and if you post something in the comments section or email him he might be able to give you some pointers.
Jordan

Sent from my SM-N986W using Tapatalk

[harv]

Troy, I don’t know anything about power brakes on Series LR’s, but reading your post makes me question your gauge. Assuming your gauge is in inches of mercury, sea level air pressure is about 30”, so a total vacuum would only be 30”Hg. I doubt that your vacuum pump is that good. If your gauge is in psi, sea level pressure is 14.7.

[troy]

Harv good point I have to look at my gauge again .

[oldgravy]

Teri Ann did a bunch of writing on brake upgrades in series trucks. Sounds like you're well past that point however and might just need someone to look over your setup. Let us know what you discover!