MK7 Golf GTI Coolant Leak

[Lucas_R]

does anyone know whats best to use on the waterpump union tube (to oil)... installed a replacement waterpump the other day and thought it was all gravy but after about 15 - 20 mins of letting the car run it leaking like crazy and making some crazy hissing sound like a hose or something has come loose possibly the union is not sitting properly.. had some pressure spraying and steam / water coming from that area... i used a bit of coolant on the o-ring in the union like ive seen on a video / thread somewhere but am seeing sillicone lubricant grease or even sealant is best.

Possible that you have either damaged the o ring or pushed the o ring off the union when installing it perhaps. I would have thought some type of silicone grease (even Vasoline) would be necessary on this part to ensure it goes into its spot securely.

I had my mechanic replace the waterpump in my Mk7 GTI a few months ago. I was going to do it myself, but just seemed like a huge amount of stuffing around and the chance of breaking something or not having the right tool at some point would be high. He said he does 4-6 a week and knows all the tricks - so he got the job.

[amunra]

yeh if u have someone good that can do it at a sane price then its a good option im stuck remotely so have all the tools.

i used coolant on the orings for the union like has been said can be done but will try some sillicone spray when i undo it all and have a looked.. could have been a hose but probably union

[amunra]

turns out it was the new union that failed or i failed something installing it the 1st time but not sure how...

removed the pump for the 2nd time when it failed a vacuum test (had one delivered to test this) and removed the union and noticed there was a bit of play on the orings. the old union popped into the old pump quite nicelly and noticed the new union didnt do quite the same ... tested it onto old pump and noticed the ring had alot of play while going in.

ended up using the old union with a small amount of sillicone spray and then pressure tested it and it stopped making that heavy leaking noise from the union area.. put it all back together ran the car and seemed to stay dry so probably worked.