GU Vacuum Pump Repair

[BillsGU]

Just wondering if anyone has ever replaced or repaired the vacuum pump on a ZD30 GU? Mine has a problem and I can't find any reference to repairing it. Nissan want about $600 for a genuine new one - what a surprise.

[MudRunnerTD]

Sorry Bill, not sure about the ZD30 but on a TD42 they are serviceable and fairly simple. The TD42 runs like an Impeller but with renewable fins. That's it. Simple. Are you sure you don't just have a vacuum leak?

[BillsGU]

Sorry Bill, not sure about the ZD30 but on a TD42 they are serviceable and fairly simple. The TD42 runs like an Impeller but with renewable fins. That's it. Simple. Are you sure you don't just have a vacuum leak?

Is the TD42 pump built in to the alternator? Anyway, the ZD30 has a pump that runs off the engine.

There is no leak. The system holds vacuum with the engine off. The booster checks out OK but the pump cant sustain vacuum once the brake is pushed a number of times. I have been told that it is not repairable - it must be replaced.

[MudRunnerTD]

Is the TD42 pump built in to the alternator? Anyway, the ZD30 has a pump that runs off the engine.

There is no leak. The system holds vacuum with the engine off. The booster checks out OK but the pump cant sustain vacuum once the brake is pushed a number of times. I have been told that it is not repairable - it must be replaced.

Yeah sorry bill, ZD30 is not my strong suit. I have certainly had the vac pump out of my GQ stripped down and understand its inner workings.

What you describe is not inconsistent with how the Vac pump delivers on the TD though, how many pumps before you start running short of vacuum? Is it getting worse? Surely this must only really happen on long down hill descents?

On the TD the vac pump also supports the Clutch. I have seen a guy add a larger vac canister to increase storage for better performance.

Sorry can't be much more help mate. I can't imagine that it would be a common failure, can you chase a second hand one?

[Alitis007]

Are you pumping the brake pedal at idle or while the car is driving?? If its at idle it could be coz its not turning fast enough. What happens if your in park and idle up the motor, say to 1500rpm???

[BillsGU]

It happens after a couple of pumps while the car is driving, and it is getting worse. I picked up a second hand pump this morning and will fit it over the next couple of days. Even the wrecker said they don't sell many as they don't fail very often. Just lucky I guess! Might go and buy a lotto ticket...........................

[Robo]

How many reserve vac cylinders does it have 1 or 2 ?.
seems some have 1 and some have 2.

my gu td42t has 2.
but I recently came across another that only had 1, and it was a year younger than mine.

[BillsGU]

How many reserve vac cylinders does it have 1 or 2 ?.
seems some have 1 and some have 2.

my gu td42t has 2.
but I recently came across another that only had 1, and it was a year younger than mine.

Mine has one - but it has workd fine until recently - so that is not the problem. I'm in Sydney at the moment so I won't be able to swap the pump until next wek. Hopefully all will be good then.

[Hodge]

I'll be keeping an eye on this as my pump is suspect too. Clutch is assisted by vacuum too isnt it?

[BigRAWesty]

I'll be keeping an eye on this as my pump is suspect too. Clutch is assisted by vacuum too isnt it?

Yes.. You may simply have a leak in a vac line.
I'm not sure about petrols but the td42 has a canister on the passenger side on the firewall or over wheel arch with is a vac tank. Follow the line from the pump to this tank and feel the pressure, then pop the line off at the clutch or brake booster and feel the pressure.
It should be a noticeable pressure build.

[BillsGU]

Yes.. You may simply have a leak in a vac line.
I'm not sure about petrols but the td42 has a canister on the passenger side on the firewall or over wheel arch with is a vac tank. Follow the line from the pump to this tank and feel the pressure, then pop the line off at the clutch or brake booster and feel the pressure.
It should be a noticeable pressure build.

Better to use a vacuum gauge. That way you can build up vacuum, switch the engine off and then see how long it holds. There are spare ports to tap into near the vacuum tank.

[BigRAWesty]

I'm not sure the amount of vacuum created woukd show on a gauge

[BillsGU]

I'm not sure the amount of vacuum created woukd show on a gauge

Mine shows around 25 in/Hg (about 15 PSI), it just takes a while to get there due to the pump problems. It's higher than you may think. It should stay there for a while (with engine off) if there are no leaks as there is a non return valve at the tank input, so it can't bleed back through the pump.

[nissannewby]

I'm not sure the amount of vacuum created woukd show on a gauge

As bill has said it certainly does. Absolute vacuum is 30in/hg.

[BigRAWesty]

Well there ya go. Never though it was that high lol.

[BillsGU]

Replaced vacuum pump today and all is now good. I'll pull the old pump apart during the next few days and see if anything looks worn.

[BillsGU]

Well there ya go. Never though it was that high lol.

Must be a bit of (negative) pressure there as it has to be able to move the vanes in the turbo - among other things.