Thread: 300Tdi Waterpump housing CRACKED?!

Hi All,

As the title suggests, my water pump housing on my 300Tdi has cracked, or rather appears to have cracked. So I went out and bought a genuine parts water pump and gasket and changed it out, note: I also changed the P-Gasket at the same time as this gets disturbed when changing the water pump.

So re-filled with coolant, ran up to temperature and low and behold the new pump starts leaking in exactly the same place. So I did some more research and found that the aluminum casting that the water pump sits in can warp, well fine I thought, so I went a bought a new casting (part number ERR3637), another new water pump, new gasket and another P-Gasket.

I changed the whole lot today, re-filled with coolant and run up to temperature. The new pump has cracked as well, in exactly the same place! I am at a lose end to explain why this has happened to all three pumps. All the bolts were torqued to 25NM as per the manual. The orginal pump had done in the region of 10,000Km before the crack appear, but the following two didnt even make 1km. The engine was a reconditioned unit from Turner Engineering in the UK.

This was the original first crack:



You can just see the hairline crack to the right of the bolt head:



Aluminum Casting removed (first attempt at repair):



Not very relevant, but shows the new casting all fitted up:



So any ideas what is going on with my engine? Could the acutal block be warped? It's not loosing any water, the cooling system doesn't appear to be pressured and there is no water in the oil.

Cheers

Rob

None of the bolts were bent and they are the newer coated type. All mating faces were checked to see if they were true and all were flat on a straight edge.

The fracture is happening on the same "web" on each water pump (I have now been through three genuine pumps including the original). All bolts were torqued up to 10Nm first, opposite side/alternating, then going round them again up to 25Nm as per the manual.

I have owned 300Tdi's for 10 years plus and I have never seen this type of failure before.

A friend who is a NDT Technician carried out some dye penetrant testing on the pumps and this has confirmed that they have all fractured in the same location. I am at a loss as to why the first one lasted 10,000km and the second and third didn't even make 1km.

Please see pictures below of NDT results, the red line is the crack:

Both the pumps with red marker dye sprayed on, the original pump is the lower one in the picture.



Rear of the pump with the fracture in red (original pump):



Front of the original pump:



Front of the 2nd pump clearly showing the fracture:




Rear the of the original pump, alternator and PAS pump housing (Part no. ERR3736) where it bolts up to the block, no signs of fractures:




Note that the third pump was still on the vehicle at the time of testing, but it has definitely fractured in the same location.

Having had a chat with a friend, we are thinking that the gasket maybe too thick and as the pump is tightened up this is causing it to distort, why this is the case I do not know, because as I have said all the faces as flat. I am going to try one more new pump with just RTV silicon as the gasket. If that fails I am completely out of ideas.

Cheers

Rob