Had an MOT last month and although the car passed the tester told me I had an oil leak down the back of the engine. When I looked from underneath, there was quite a bit of oil on the back side of the block. It seemed to be from the head gasket down on the rear of the engine. It was only on the rear towards the air filter side.

 

Since there was no oil above the head gasket I was sure it was not from the cam cover. Although it was exactly from the head gasket down I was also sure it could not be the head gasket, why would that just leak oil, I had no cooling system issues. I guessed the oil must be coming from the tandem pump and on checking close up the oil was coming from between the tandem pump and the cylinder head.

 

Doing some web reading that tandem pump gasket is a common failure, so I got a replacement 038145215 gasket for £10 and swapped it over.

 

Not a hard job, about an hour in total. Had to use a vacuum pump on the diesel fuel loop to empty and refill it. I only removed the top fuel hose from the tandem pump itself, leaving the bottom and rear vacuum pipes connected. There was enough room to hold the tandem pump away from the cylinder head, remove the old gasket, clean up both faces and put the new gasket in place.

 

I found a good trick with my mobile phone, Remove the top engine cover and put the camera with flash on to 10 second delay, tap the photo button and quickly position the camera down the back of the engine. Then I was able to get a photo of the rear of the engine to check the leak was fixed. This is my latest photo after a month, looks as dry as a bone to me.

 

So if anybody fancies doing the camera trick it is worth having a look as before I went to MOT I had no idea I had that oil leak.

 

 

Thanks for the useful tips.

Until you wrote this I would have been a bit shy of going anywhere the tandem pump ,somehow believing the fuel pipes were under high pressure?

On a pd engine the only location under extremely high pressure is in the cylinder head where the fuel rail lives.

And that is only high pressure when the engine is actually running. The tandem pump pumps diesel into the head fuel rails. There are feed and return holes in the cylinder head that the tandem pump bolts onto.

 

That is why VW put the pump in that position, there are no high pressure pipes the high pressure diesel goes direct pump to head through aligned holes. With the gasket seal of course.

 

Excess diesel is returned to the tandem pump via the cylinder head to tandem pump direct mating return holes and pressure regulated. Within the tandem pump before coming out the bottom hose connection and returning to the fuel filter.

Thanks to both for your replies,it through forums like this that you learn so much.

Must be the common rail engines that the pipes are under great pressure,or perhaps Ive got that wrong as well.

Thanks to both for your replies,it through forums like this that you learn so much.

Must be the common rail engines that the pipes are under great pressure,or perhaps Ive got that wrong as well.

PD and CR engines both have ridiculous fuel pressures - when they're running.