Brake issue after pulling engine

steelholder · Apr 16, 2026

Hoping you guys can help with a brake bleed issue that I'm having. I recently pulled my engine and have put it back in. Engine is running fine, however, now the brake pedal has all the symptoms of air in the brake system, but I can't figure how that could have happened. The first time I pumped the brake., it works well but the second, third and fourth time it gets very stiff and is not responsive at all, I give it ten seconds or so and I get one good brake pump. What would you guys check here? I have no idea how to bleed the brakes in a truck like this.

ihc1470 · Apr 16, 2026

Sounds like you have low vacuum, might check that all the hoses got reconnected.

DirtyWood · Apr 16, 2026

If you have a vac gauge I would test the system and you should have 26 inches of vacuum at idle. The belt on the vac pump does not need to be overly tight either.

FrozenMerc · Apr 16, 2026

Think about what you changed. Assuming you did not open the brake system during the engine swing, so there should be no way for air to get into the system. As Dirty and IHC alluded to, you probably did mess with the vacuum pump during the engine swing. Start there.

Is it making good vacuum?
Is there a damage to the vacuum line?
Did you hook the vacuum line up to the outlet of the vacuum pump?

steelholder · Apr 16, 2026

I think you guys are right about a vac leak. I replaced one hose that was there before the engine pull but that hose leads to 2 ends that are no connected anywhere. Can you guys take a look and help with where these two ends are supposed to go? I taped both ends to see if it would help but no go. Bottom picture stems from the T fitting on first pic.

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IDIBRONCO · Apr 16, 2026

Generally those have something to do with the HVAC controls. Those plastic vacuum lines are notorious for breaking. NOT one of Ford's better ideas. Look around your heater box. You should be able to see where at least one of them attached. Why not get some small diameter fuel line and attach the two ends? The worst that will do is nothing. It just might solve your vacuum leak.

steelholder · Apr 16, 2026

IDIBRONCO said:
Generally those have something to do with the HVAC controls. Those plastic vacuum lines are notorious for breaking. NOT one of Ford's better ideas. Look around your heater box. You should be able to see where at least one of them attached. Why not get some small diameter fuel line and attach the two ends? The worst that will do is nothing. It just might solve your vacuum leak.

Thanks. Might you guys be able to check in your trucks where those two lines lead to and post a pic here?

Heymack · Apr 18, 2026

Here are a couple shots. The short hose goes into the evaporator core housing. The long end goes into the vacuum block mounted to driver side inner fender (on my '93). The last leg goes into the HVAC wiring harness, and presumably into the cab to operate vents.

Heymack · Apr 18, 2026

Couple more pics

DougBoy66 · Apr 19, 2026

You will know if it goes to the HVAC also because if they are not attached you cant change from vent to floor to defrost until they have vacuum

DougBoy66 · Apr 19, 2026

another thing to consider, if you find that you have solved all your vacuum issues and are still having the pedal fade, I had that issue because of the RABS. If the wiring got dinged up when the engine was pulled it might malfunction. Mine just let brake fluid by the valve all the time so the pedal was always mushy.

steelholder · Apr 20, 2026

Heymack said:
Couple more pics

Thanks!!

steelholder · Apr 20, 2026

DougBoy66 said:
another thing to consider, if you find that you have solved all your vacuum issues and are still having the pedal fade, I had that issue because of the RABS. If the wiring got dinged up when the engine was pulled it might malfunction. Mine just let brake fluid by the valve all the time so the pedal was always mushy.

I think my issue is directly related to the brake booster which I'm getting today. I will report back and let you guys know if that solved it

steelholder · Apr 21, 2026

Unfortunately this did not solve my brake issue. The booster did need replacing though. The old one was pretty corroded and had an old leak. The hissing sound at the pedal stopped but the symptoms persist.

Symptom - (all within a 10 second period) 1st brake press works great, truck reacts immediately and stops, 2nd press feels much stiffer and significantly fails to stop the truck, 3rd and 4th press very stiff and little to no reaction in stopping the truck. If I let off the brake for about 15 seconds or so the cycle repeats.

steelholder · Apr 21, 2026

DougBoy66 said:
another thing to consider, if you find that you have solved all your vacuum issues and are still having the pedal fade, I had that issue because of the RABS. If the wiring got dinged up when the engine was pulled it might malfunction. Mine just let brake fluid by the valve all the time so the pedal was always mushy.

What is the RABS?

Brake issue after pulling engine

steelholder

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ihc1470

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DirtyWood

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DougBoy66

That is a HORRIBLE idea!!!!!! What time?

DougBoy66

That is a HORRIBLE idea!!!!!! What time?

steelholder

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