This LRO reader emailed LRO.firstname.lastname@example.org looking for guidance and advice on a tricky Defender 300Tdi vacuum pump situation.
My 1996 300Tdi Defender 110 station wagon has suffered three brake vacuum pump failures in only two years.
When the original pump failed, it was replaced with a brand-new Wabco fitment, which lasted about 10 months. This was replaced with another new Wabco pump, which only lasted a couple of month. I then fitted a third new Wabco pump last spring, which has also just failed.
In all three cases, the return spring on the pump plunger broke, so the plunger no longer makes contact with the cam lobe. I’ve now fitted a new Britpart pump.
Have I been unlucky with a batch of faulty Wabco pumps, or is there an underlying problem that could cause the pumps to fail like this?
Ross Sibbald, Hawick, Selkirkshire
The pumps have to be fitted correctly with No 1 cylinder at TDC, then the fixing bolts tightened gradually. Assuming this has been done, there must be another reason.
There was a faulty batch a few years ago, but you’d have to be unlucky in the extreme to get two from that batch. The only time I have ever come across vacuum pumps failing this regularly was due to damage on the camshaft lobe that runs the vacuum pump; it was basically thumping the pump position rather than running it smoothly.
It may be worth removing the pump and checking the cam lobe.
Wabco is original equipment fitment for the 200Tdi so the quality ought to be fine. Even though these vacuum pumps have always been a weak point, they should certainly work for much longer than 10 months.
This workshop advice appeared in the September 2015 issue of LRO. Back issues are available to download on digital devices here.