Thread: Replacing TDi300 vacuum Pump & using longer bolts?

Screwing the pump back on against the tension of the pump spring may cause the pump body to crack, as it is plastic. It may never happen, but if it does you're up for another pump.
The engine doesn't have to be on top dead centre, all you need is to have the cam lobe on it's base, the lowest lift point of the lobe. It would have taken maybe half a turn of the crank to get onto the base of the lobe, Regards Frank.

Originally Posted by Robmacca

Guys....

I finally got around to replace my leaky Vacuum Pump today and I know the manual says to ensure your engine is TDC b4 removing the pump. I took the chance w/o checking on TDC and removed it. When I checked, the lobe was almost at the worst spot it can be for re-installation... Anyhow I check the depth of where the bolts screw in and noticed that there is a fair bit of depth there, so I just refitted the pump using longer bolts and tightened all bolts up and then slowly replaced the longer bolts for the original ones....

It got me thinking.... Why couldn't I just leave the longer ones in there all the time ?? Is there a reason the factory ones are that particular length??

just curious.....

Plastic ? Both the one on my car and the spare are both cast iron or alloy but definitely not plastic.
I removed and replaced mine against the cam and apart from making it slightly harder there is no il affect.

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Loanrangie, you're right, could have sworn it was plastic, it looks like powder coated Diecast alloy, which is even more brittle than plastic.
Plastic has some give, Diecast alloy has none, it is so easy to turn the crank so as the pump drive is not under tension, I don't know how strong the spring in the pump is that you have to compress, but LR recommends having the lobe at the base to make installation easier, to each his own, Regards Frank.

Originally Posted by loanrangie

Plastic ? Both the one on my car and the spare are both cast iron or alloy but definitely not plastic.
I removed and replaced mine against the cam and apart from making it slightly harder there is no il affect.

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Unscrewing it against the spring will also crack it. Unscrew 3 and it will crack at the 4th. Been there, done that.

Originally Posted by damienb

Unscrewing it against the spring will also crack it. Unscrew 3 and it will crack at the 4th. Been there, done that.

Must have been unlucky , i have removed 3 without a problem.
Possibly was damaged before ?

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Originally Posted by loanrangie

Must have been unlucky , i have removed 3 without a problem.
Possibly was damaged before ?

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So using slightly longer bolts is not a problem then....?

Originally Posted by loanrangie

Must have been unlucky , i have removed 3 without a problem.
Possibly was damaged before ?

Sorry, I should have written "may" crack it. This was an old pump (with the head gasket fix) that was being replaced anyway. I've changed these many times and to be honest still don't worry too much about TDC until refitting.

Originally Posted by Robmacca

So using slightly longer bolts is not a problem then....?

no.

for future reference. the cmshaft has 2 lobes for the vac pump and they ollow #1+4 so if your on or within 90 degress of TDC your going to have issues torquing it down correctly, if you undo or tighten the moutning bolts 1/4 a turn at a time you can get them on and off without breaking them every time but its a lot more hassle than it needs to be and you may not get the gasket to seal properlyl if you only goto the nominal torque etting.

font foget to use 2 gaskets or make new one out of extra thick gasket paper before you replce it as this help reduce the maximum pressure put on things and in some cases (mainly on non gnuice bitpart part) prevents the piston from topping out