300Tdi Vacuum Pump

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Originally Posted by rangieman

Well i can tell you for a fact that if you hook up a 12v vac pump to constant power it will suck the booster inside out this is why it needs to be switched on and off some how when vacuum is near low :eek: Maybe the mechanicle pumps run some sort of by pass vacuum valve only a guess :cool:

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This I gotta see. Pics??? How much difference is there between 25 ins vacuum from a decelerating V8 engine and 30 ins of pure vacuum? Not enough to damage a booster designed to have a margin of safety.

Electric vac pumps have switches to stop them running continuously. Mechanical vac pumps stop stroking full travel as its only a spring that causes the vacuum. High vacuum holds the diaphragm back. Also the valves nearly stop moving and so don't wear out as fast.

EV conversions use electric vac pumps to run boosters, read some EV forums if you want to find about fitting up electric vac pumps. Apparently some Volvo turbos ran them.

I would be looking further if you are doing pumps all the time,have you checked that it's not deadheading?,it may just need a spacer. Pat

Could it be that when there's sufficient vaccuum in the circuit that the plunger is retracted from the lobe and does not make contact, hence wearing less and prolonging pump life

It hasn't been an ongoing problem for me. This is the first replacement in almost 200,000km.

I hope the next one lasts as long.

I read a suggestion on one of the many posts on this subject that it was worth fitting a second gasket as a spacer between the pump and the block. Is that supposed to be a good idea in all cases or only if it is deadheading? I'm guessing that means the piston is contacting the top of the chamber.

My original pump failed with a broken spring.
The extra gaskets was recommended by Karcraft when I purchased the new pump, and yes they have an interest in selling more gaskets, but at 65c (IIRC) they are not going to get rich.


Martyn

Good to know that I am not alone. I am about to go on to my 4th pump. Only got 53k's out of the last pump before the same old problem with lack of brakes. I have a 300 series Defender that I bought new in 1996 and it has done only 128,000ks. The original pump lasted 15 years. Now 3 pumps in two months:mad: I have lost faith in the reliability and about to have pump number 4 installed. Pump 3 failed while going down a hill:o It is hard to remain faithful to the green oval when trips have become potentially dangerous.
landychris

Chris, I've installed a Bearmach vac pump in place if the WABCO and so far so good, but it's only seen 10-15,000km so far.

Reports from here and the UK suggest the Bearmach version is far more reliable.
I hope so.

I installed a cheaper indian type pump at the recommendation of karcraft - it's been fine for a recent 15000km return trip to W.A.

I had rebuilt my orig Wabco at about 160000km but the actual suction was diminishing (not noticed by me I might say) - But I did notice decreased brake pedal pressures when I installed the above item.

Karcraft & most other knnowledgeables seem to recommend at least a double thickness of gasket - I can see that fitting three may also be a good idea - limits pump stroke to save wear in pump body.

Pump number 4 is in, 100k's and all ok ......yeah:(
landychris

Too many pumps too late... my 4th replacement has died and I'm now looking at 12v vacuum pumps to replace it.

Sick to death of the poor quality of the Wabco units. The design is just so flawed.

3 of the pumps failed by seizing on the main piston spring and you get that loud tap tap tap sound as the loose rod is being slapped back up into the pump. Basically replaced under warranty.

Now the last one only traveled <1800km but is out of warranty.
Pump is not producing vacuum.
Pulled the top of and found that the main piston seal has failed and bits of the seal lip got caught in the one-way valve keeping it open.
Piston action is still good and free, tested the valves work correctly and holding pressure before putting the top head back on, but the piston seal is fully compromised and not able to pull a vacuum.

So looking at "SSBC 28146 Electric Vacuum Pump Kit Comp 5500"
or Thomas Thomas Industrial Diaphragm 12 Volt DC Vacuum Pump or Compressor model 107CDC20-898
or Summit Racing Part Number: SUM-760152

Will be operated by a relay and pressure switch.

Any thoughts which electric vacuum pump to get?
Anyone else done a conversion on their 300TDI ?
This will be going on a 130 Defender.

Cheers