After 3 pumps hard brake pedal

Hi there, I have found that after 2 pushes on the brake pedal in a row while driving the 3rd one is rock hard. The brakes worked fine with the TB42 petrol engine in it, the booster worked fine. Since I put the TD42 diesel engine in it with the vacuum alternator & a little bigger than factory vacuum canister with the one way valve the brakes are nowhere near as good. Is this common with alternator boosted brakes ? I have four wheel disc brakes off a EFI GQ, with a new master cylinder. Cheers Grant.

Sorry don't know the TB, are the brakes vacuum brakes on the TB or have you converted them?

Yep you have a vacuum issue with the boosters.
You'll probably find clutch is stiffer also (if also boosted).

Simply find the first join in vacuum line and pull out apart. Start the engine and stick your finger over it. You should notice a good pressure build up.
Repeat on the hose at the booster.
If different then you have a leak and it's simply a matter of elimination. Test each join.

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Originally Posted by MudRunnerTD

Sorry don't know the TB, are the brakes vacuum brakes on the TB or have you converted them?

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Yes the TB42s engine run the same boosters on the clutch & brake. The TB42 gets its vacuum from the inlet manifold instead of the Alternator pump .

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Originally Posted by Westy's Accessories

Yep you have a vacuum issue with the boosters.
You'll probably find clutch is stiffer also (if also boosted).

Simply find the first join in vacuum line and pull out apart. Start the engine and stick your finger over it. You should notice a good pressure build up.
Repeat on the hose at the booster.
If different then you have a leak and it's simply a matter of elimination. Test each join.

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OK will try this tomorrow. The first join is the one way valve on the canister, then there's the one out of the canister that goes all the way to the booster T piece. The canister is up the front near the LH head light, then the hose goes all the way across the engine at the front to the rear firewall. Does it matter how far away the canister is mounted from the boosters ?

G`day mate
You may have a faulty Vacuum pump to check put a vacuum gauge at any convenient place and see if you get a min of 23 inches of mercury. This is about the max vac you will be able to get. If low get the gauge as close to the pump as possible to eliminate it. If the pump is OK then do as Kallen says and eliminate any leaks,if no leaks are found check all the hoses for collapsing as they do get soft and collapse this can happen internally and you wont be able to see it from the out side. To check the hoses start with the gauge at the pump and check at each join or just replace the lot. If my memory serves me correctly ADR rules state you must get 4 applications with vacuum with the engine turned off.

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Originally Posted by pearcey

G`day mate
You may have a faulty Vacuum pump to check put a vacuum gauge at any convenient place and see if you get a min of 23 inches of mercury. This is about the max vac you will be able to get. If low get the gauge as close to the pump as possible to eliminate it. If the pump is OK then do as Kallen says and eliminate any leaks,if no leaks are found check all the hoses for collapsing as they do get soft and collapse this can happen internally and you wont be able to see it from the out side. To check the hoses start with the gauge at the pump and check at each join or just replace the lot. If my memory serves me correctly ADR rules state you must get 4 applications with vacuum with the engine turned off.

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The Altanator is brand new so is the hoses & the vacuum canister. I will do the test tomorrow. THANKS.

Well the vacuum at the first join is the same as the connection at the booster. I don't have a vacuum gauge unfortunately.
Maybe my booster needs re-kitting. The hose I used from the pump to the vacuum canister & booster is transmission hose but that shouldn't matter.

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Originally Posted by Lightspeed

Well the vacuum at the first join is the same as the connection at the booster. I don't have a vacuum gauge unfortunately. Maybe my booster needs re-kitting. The hose I used from the pump to the vacuum canister & booster is transmission hose but that shouldn't matter.

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Yes it will matter a hell of a lot!! trans cooler hose is made for pressure brake booster hose is made for vacuum, the trans cooler hose is reenforced to stop it from ballooning and the booster vacuum hose is re reenforced to stop it collapsing. See the difference ?? Better replace it to the correct hose for your's and your family's safety.

Sorry if i come across rudely.

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Originally Posted by Alitis007

Yes it will matter a hell of a lot!! trans cooler hose is made for pressure brake booster hose is made for vacuum, the trans cooler hose is reenforced to stop it from ballooning and the booster vacuum hose is re reenforced to stop it collapsing. See the difference ?? Better replace it to the correct hose for your's and your family's safety.

Sorry if i come across rudely.

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OK will do thanks.