Truck: 1998 Ford F800 (Lucas Girling Brakes)
Initial Problem: Rear wheel brake cylinders leaking on both sides. (Remove and replace)

Summary: After replacing the rear wheel brake cylinders on both sides of the vehicle, we ran into issues #1 & #2 I listed below.

Issue #1: Electric brake indicator on dash won't shut off even after decompressing the parking brake.
Issue #2: No drive or reverse (but nothing wrong prior to brake job)

Work Performed: Replace both left & right of the rear wheel cylinders (front and back position). The tech doing the swap, didn't exactly know what he was doing but took on the job to swap the cylinders nonetheless (got to learn some time). While removing the back position cylinder, my tech did not cage the chamber and did not drain the chamber properly. So when he was removing the chamber line, it practically exploded fluids everywhere after it was completely loosened. He completed the replacement afterwards (both sides). After putting everything back, he topped off the fluids, bled the brakes (both types), top off fluids again.

He started the truck and put it in reverse to move it out of the shop. The trans wouldn't engage, so no forward or reverse. My seasoned tech says the problems can't be related, but the truck drove completely fine before this brake job, even my seasoned tech is stumped. We checked the fluids again and it's all good. We checked the shift linkage to the trans and it's moving normally, no pinching or dragging. What are we not grasping?

Any help or advise on both of these issues will be greatly appreciated.

 

Is it possible that the PCM won't let you move because the brake light is on?

The brake light might be tied to a proportioning valve (if it has one). With the rear hydraulic pressure completely gone, the proportioning valve will move all the way to one side preserving pressure for the front, and light the brake light. It's possible it stuck, or there might be a procedure to reset it.

 

Thanks for the reply!

Are you referring to the regular braking system or the parking brake? The proportioning valve is for the regular brakes, I don't think the parking brake is the same. (the parking brake is what lost all pressure when it blew in his face)

 

But the "regular brakes" are also the cylinders he replaced, yes?

I'm not a Large Truck guy, was just trying to help the conversation along

 

I appreciate that. Technically yes, the cylinders he replaced are for the brakes. When the brake pedal is applied, it pushes both front and back position cylinders to stop the vehicle. When the parking brake is applied, it only pushes the back position cylinder to hold the vehicle. The light and buzzer should function while the parking brake is applied.

Today, I jumped on the vehicle myself. Only working on the driver side; I drained the chamber, caged it, adjusted the cylinders, and reassembled (doing it properly meant no fluid blew up in my face lol). I don't know what exactly it did but now the light doesn't even come on anymore when the parking brake is applied, which it should. The light should come on as the buzzer sounds when the p.brake is applied. It now just flickers for a second after releasing the parking brake, but does shut off. Before it wouldn't shut off at all, now it won't turn on. I'm about to do the passenger side now hoping that by some luck I can get it work work properly. I'll check back in after. If anyone has any ideas, please list them. I'm still stumped on this damn truck.

On a side note, we still have no forward/reverse after I did the driver side.

 

So here's what we have concluded.

Issue #1: Electric brake indicator on dash won't shut off even after decompressing the parking brake.
Diagnosis: After re-doing the brakes on both sides, and following proper procedure, I'm no longer worried about the EBI (at the moment). The indicator may or may not work due to some damaged wiring, but the buzzer works as intended, and the brakes work as intended (both hydraulic and parking). We will diagnose the indicator light later.

Issue #2: No drive or reverse (but nothing wrong prior to brake job)
Diagnosis: We determined that the throttle valve cable (or detent cable) is defective. After jacking up the rear end and shifting into drive/reverse, we tapped/pushed the housing where it mounts into the trans and the tires would begin to rotate. After every shift, the tires would not rotate unless tapping/pushing in on the housing. So hopefully after replacement, we won't have any more issues when shifting. Then focus our efforts on the EBI.

I'll reply again at a later time when we resume work. This truck was a vehicle we deemed 'retired' but I decided to begin repairs on it when we had a slow day and nothing else to repair. It's a 'back burner' job that is at no point a priority in our shop.

I wanted to throw out this reply in case it may help anyone else having similar issues.

Don't let inexperienced mechanics work on your vehicle unless they are under strict supervision or after doing heavy research on proper procedures. That was the mistake we made. My seasoned mechanic hasn't done girling brakes since the 80's so he didn't remember the procedure. We should have done the research prior to starting the repair. Luckily this was a 'retired' vehicle and not a vehicle currently in use. (on a side note; it's also the only truck in our fleet with girling brakes)

We don't have an actual manual but here are the steps for girling brakes:

Removing Girling Brake System
Note: I'm not listing wrench/socket sizes required, that's self explanatory during the removal process.
1. Chock wheels
2. Release parking brake
3. Remove tires
4. Crack bleeder valve so fluid may escape
5. Crack drain plug so fluid may escape
Note: with both the bleeder valve and drain plug cracked, give it about 3-5 minutes to purge the pressure by itself
6. Open drain plug completely allowing all fluid to drain, then completely remove bleeder valve.
7. Cage brake chamber
8. Adjust brake shoes to remove drum if drum is stuck. ('shock' the drum by hitting it a couple times w/ 4lb sledge if necessary when drum is still stuck)
9. Loosen hard-line mounting bolt on chassis (doesn't necessarily need to be removed, just loosened to allow movement)
10. Disconnect all hard-line connections (small and large)
11. Remove fitting (for large hard-line) on brake chamber
12. Rotate chamber to remove from rear position cylinder
13. Remove brake shoes
14. You can now replace the cylinders
Note: If you plan to replace the entire assembly (you can purchase the entire assembly with shoes and backing plate), you must remove the axle assembly on that side (skip steps 13 &14 since the assembly can be removed in 1 piece)
15. Re-install everything using a reverse process

Bleeding Girling Brakes
1. Apply parking brake.
2. Check fluid levels.
3. Chock the wheels.
4. Fill reservoir. (Mercon LV)
5. Start engine, run for 2-3 minutes
6. Pump brake pedal several times (10-15 times)
7. Check parking fluid level.
8. With engine running, cycle the parking brake release and applied. (5-10 seconds in between each position)
9. With engine running, release parking brake. Bleed the left-hand side first until no signs of air or bubbles. (DO NOT allow reservoir to empty)
10. Repeat steps 8 & 9 for the right-hand side.
11. Fill reservoir as needed.
Note: Check parking fluid levels when parking brake is applied.

 

Good info there! I recently bought a 1999 F800 with Lucas Girling brakes and both cylinders are leaking on the drivers side. Can they be replaced without removing the parking brake chamber and the backing plate? Thanks!

 

If you are just replacing the cylinders, yes. You do not need to remove the chamber and backing plate.