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[Brynjaminjones]

Evening all, I've just been out for a spin in the XJ after an oil change and general fiddling under the bonnet. Almost went head on into another car in the lanes when I braked and had no servo assistance!

The pedal was very stiff, and I'm confident the servo isn't operating.

Under the bonnet there is a very definite hiss coming from the top of the intake manifold near the bulkhead.

The Jeep is idling fine.

Would a vacuum leak small enough not to cause a different idle be severe enough to not allow the servo to work?
After sitting for a few minutes idling, the servo had build enough vacuum to last one more brake application.

Also, what's the best way to locate the leak precisely? So far I've failed!

EDIT: I'm confident there must be a vacuum leak as a couple of times when opening the bonnet the engine revved as I lifted it; I assume as a result of the changing airflow?

[daggie]

hand held garden sprayer filled with water

[Dave69]

add some washing up liquid to the water you put on the vacuum hose.

there should be a long piece of hose from the brake servo to a take off point normally on the air intake to the engine. check the hose for splits or cracks at each end, or just change the hose anyway as a precaution. Age and heat does cause these to crack and split.

At least you didnt scream "my brakes failed"

[Brynjaminjones]

there should be a long piece of hose from the brake servo to a take off point normally on the air intake to the engine. check the hose for splits or cracks at each end, or just change the hose anyway as a precaution. Age and heat does cause these to crack and split.

At least you didnt scream "my brakes failed"

I straight away knew it had to be something I'd disturbed, and I had fiddled with vacuum lines earlier.

After much hunting, I've found by using a stethoscope that's it's the hose going from the rear CCV elbow on the valve cover to the intake manifold.

Let's hope I can find a replacement on a Sunday...

[Dave69]

If its rubber use super glue abd wrap with insulation tape as a temp fix