Technical HGT water pump

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Technical HGT water pump

May 19, 2006
Tonbridge, Kent
Hi folks

I have been changing the cambelt and water pump on my HGT (2002 CF3 engine) and have been having problems getting the water pump to seal. On two occasions now the O-ring has either failed to seat properly or has been trapped and broken. With the third attempt coming up I am getting a bit bored with the whole thing and wondered if anyone had done this job without the O-ring and just relied on a decent application of RTV sealant? That's the approach for the FIRE engine, after all.

Else I guess I will try honing the housing with some wet and dry, and might try sticking yet another O-ring to the pump with a small amount of sealant - and maybe supplementing with more sealant on the O-ring and mounting area. Though I worry if the O-ring doesn't seat again, it won't seal, sealant or not, hence the idea to just abandon the O-ring altogether.

Just in case anyone has experience....


O-ring must be free to move (and seat into place), lubrication helps during assembly. And paying attention.
Most common mistake (misunderstanding) is using adhesives on o-rings! It doesn't help. You're making it worst.
O-ring is locked and does not play any role no more (you can remove it completely then and use sealant alone).

O-rings must have proper mating surfaces, seats: shape (round hole in this case + flat surface), size, surface finish (corrosion).
You must check what's missing, what's wrong with the picture (is there corrosion damage, hole out of shape/size etc.).
If there's a wear (and sanding will enlarge the o-ring seat/groove, whatever), you can try using oversized o-ring (+0,5 mm thicker for example).
I don't think it would affect the sealing but the water pump's have a different size pulley depending on the year of the engine, maybe the sealing face is slightly different? I think there the same.
Hi - yes I'd previously been caught out by the different pulley sizes (71mm for CF2, 68mm for CF3) but I know I have the right pump now. Pretty sure the other side of the pump is the same in all cases....

Hoping to have an update, one way or the other later today....
Just to belatedly conclude this - I spent some time cleaning up the sealing face in the head with very fine wet and dry, used a Marelli O-ring (provenance of previous seals unknown) and put a bit of sealant on the outer edge of the O-ring, and fingers crossed it has worked. It "felt right" as I put it on, if that makes sense....I could feel a bit of elasticity as I offered it up and then it plopped home. Nice. Can only assume the combination of some roughness on the sealing face and some dubiously weak O-rings was the issue.... Every day is a schoolday.