KV6 Small Coolant Leak at Bottom of the Water Pump
 

Recently after changing the timing belts on my sons KV6 engine we found that quite quickly the non branded belt tensioner started to make a noise, so of it came again to change it to a genuine tensioner. At the same time we found a small coolant leak coming from underneath the water pump. Initially I thought it was from the impellor shaft itself, however it was not from that. The water pump was changed out for a new genuine version, but upon assembly I found that one of the M6 threaded holes actually breaks into to cooling system. Hence upon assembly we applied a sealing compound to the screws. The workshop manual does mention about using new screws with sealer on them, but they don't really state why.

Anyway tonight I was working on another KV6 and while on the bench it is much easier to see which holes have the issues, so I thought it worth taking a photo of the offending holes that break into the cooling system. You should also note that the oil pump also has one M8 hole that also breaks into the cooling jacket, and would need a sealing compound applied.

I'm sure there are a number of KV6 engines around that possibly suffer from a coolant leak after a belt change.

Photos show block with water and oil pump removed. The screw holes have been circled in white paint. All other tapped holes are either blind or tapped through but do not communicate with any other part of the coolant jacket or oil drillings.

Thank you for posting this information Lovel:bowdown:

I didn't notice this when I replaced my water pump and oil pump a few months ago. However, I did blindly follow the advice in RAVE to fit new screws, just as well:}. BUT - the screws supplied by Rimmers for the oil pump were not the same as the original MGR ones - they were zinc coated rather than black and did not have any sealing compound. Luckily I added plenty of Loctite before fitting them.

This is the problem of writing manuals.
Don' t just say "use new bolts" when anyone can see, there is no good reason. Say "sealing bolt in waterways" and it would make sense.

Can these screws be fitted without removing cambelts and waterpump? Ever since I had my water pump and cambelt fitted over a year ago I've been having to top up around 500mls every 500 miles and pressure testing has failed to identify any leak. Sounds an interesting one to look at in more detail when I have the time if it doesn't involve taking the engine to pieces......

Not without removing a bunch of parts.

The timing belt would not need to be disturbed but the large alloy y-shaped cover needs to come off to access that water pump and set pins. Alloy y-shaped cover in photo fitted loosely just to show how much it covers.

Alternativley if you removed the rear front timing belt cover you might be able to get a borescope down to establish if leak free.

Thinking of this situation. Can anyone weight in on the following ?

If those bolts were refitted without sealant, could it be possible that the coolant pump is pumping air into the cooling system from those holes ?

I have mysterious pressure in my cooling system without any combustion gases being present.

No, that is not possible. The pressure difference of a water pump is marginal and it is designed for flow.
If you have over-pressure in a cold engine, and you have not changed altitude (barometric pressure) you can only get that from combustion gases in the coolant.

SHould I use new bolts for the KV6 water pump, as the manuals say?
I note the old ones have evidence of a sealant which having read this thread realise is essential, but what's the logic for using new bolts?

Think I've found the answer in another thread "V6 water pump bolts" , where the suggestion is no problem to reuse provided a sealer (Locktite 242?) is ude. I was leaning towards this, but needed confirmation.

Locktite 242 is a thread locker. A thread sealer will be a more correct choice in this case according to the issue above.