Water leak in the valley of my V6 - Alfa Romeo Forum
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(Post Link) post #1 of 6 Old 10-08-15 Thread Starter
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Water leak in the valley of my V6

I'm just completing a cambelt change on my 156 V6, only to find I am losing water into the valley at the thermostat end.
I've been pretty meticulous in what I've done, good quality parts, replaced all idlers and tensioner, new water pump, plugs while I had access, I've tried not to cut any corners and bought any necessary tools rather than make do. I have to admit though that I'd not fully appreciated how the water pipe through the valley was located and sealed. I didn't disturb the water pump end, however the pipe moved in it's location at the thermostat end. The work at the cambelt end was pretty much finished before I fully understood the sealing arrangement.

Initially I lost coolant rapidly once filled, so I bit the bullet and removed the thermostat housing, cleaned up all surfaces and fitted new O-rings to the pipe and to both unions to the heads. I was unable to change the O-rings at the thermostat end, so I cleaned as much as possible and carefully applied gasket sealant around the circumference of the pipe before seating it at this end. Now re-assembled, I still have a leak, albeit not as significant as before. I can't be certain which of the three fittings is leaking as none is visible, the water tracks down the end of the block, but I am fairly certain the problem is at the thermostat end.

I am about to attack this again tomorrow - does anyone have tips on improvements I can make to the sealing? Should I be using a gasket sealant, or other product, at the points where I am able to install new O-rings? If anyone has a fix which doesn't involve further dismantling then all the better, but I'm not hopeful on that score.

Cheers,
Bill.
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Originally Posted by heraldcoupe View Post
I'm just completing a cambelt change on my 156 V6, only to find I am losing water into the valley at the thermostat end.
I've been pretty meticulous in what I've done, good quality parts, replaced all idlers and tensioner, new water pump, plugs while I had access, I've tried not to cut any corners and bought any necessary tools rather than make do. I have to admit though that I'd not fully appreciated how the water pipe through the valley was located and sealed. I didn't disturb the water pump end, however the pipe moved in it's location at the thermostat end. The work at the cambelt end was pretty much finished before I fully understood the sealing arrangement.

Initially I lost coolant rapidly once filled, so I bit the bullet and removed the thermostat housing, cleaned up all surfaces and fitted new O-rings to the pipe and to both unions to the heads. I was unable to change the O-rings at the thermostat end, so I cleaned as much as possible and carefully applied gasket sealant around the circumference of the pipe before seating it at this end. Now re-assembled, I still have a leak, albeit not as significant as before. I can't be certain which of the three fittings is leaking as none is visible, the water tracks down the end of the block, but I am fairly certain the problem is at the thermostat end.

I am about to attack this again tomorrow - does anyone have tips on improvements I can make to the sealing? Should I be using a gasket sealant, or other product, at the points where I am able to install new O-rings? If anyone has a fix which doesn't involve further dismantling then all the better, but I'm not hopeful on that score.

Cheers,
Bill.
Did you get this resolved?
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(Post Link) post #3 of 6 Old 31-08-15 Thread Starter
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Yes, eventually. I removed the thermostat housing and replaced the three pairs of O-rings, though I did cheat and applied a flexible gasket sealant.
All was good with the pipe, but once under pressure I found the water pump gasket leaked, so the cambelt had to come back off to start again. This was the gasket supplied with the Bugatti water pump, it had moved under the top bolts and was only sealing by the smallest margin when initially filled. Though I can't blame anyone but myself for the problem, the genuine Alfa gasket I used when doing the job second time was much better quality and easier to install. Unsurprisingly, the job was much quicker on the second go...

If I was doing the job again, I'd remove the thermostat housing at the start to allow access to both ends of the water pipe. I'd fit the pump & associated parts in this order:
Pump to block, O-rings to pipe, top housing to pump, pipe to top housing, thermostat housing to pipe & heads.

Cheers,
Bill.
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Originally Posted by heraldcoupe View Post
Yes, eventually. I removed the thermostat housing and replaced the three pairs of O-rings, though I did cheat and applied a flexible gasket sealant.
All was good with the pipe, but once under pressure I found the water pump gasket leaked, so the cambelt had to come back off to start again. This was the gasket supplied with the Bugatti water pump, it had moved under the top bolts and was only sealing by the smallest margin when initially filled. Though I can't blame anyone but myself for the problem, the genuine Alfa gasket I used when doing the job second time was much better quality and easier to install. Unsurprisingly, the job was much quicker on the second go...

If I was doing the job again, I'd remove the thermostat housing at the start to allow access to both ends of the water pipe. I'd fit the pump & associated parts in this order:
Pump to block, O-rings to pipe, top housing to pump, pipe to top housing, thermostat housing to pipe & heads.

Cheers,
Bill.
Glad to hear you got it sorted. Did you get the o rings from Alfa or just matched the sizes at local motor factors? Good information re the gasket on the Bugatti waterpump.
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(Post Link) post #5 of 6 Old 07-09-15 Thread Starter
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I couldn't get all of the right O-rings through Alfa. They have a smaller profile than the standard O-rings I keepd in the workshop, so I had a look online and found Exact Rubber Products. Good service with quick delivery.
There are three pipes to be sealed where they enter the thermostat housing, each needs two O-rings with each pair a different size. Some of the precise sizes are shown in the Electronic Parts Catalogue, but at least one of them wasn't. The cross section on each of the O-rings specified was 2.4 or 2.5mm, measuring the aperture in the housing against the locating grooves in the pipes confirmed this profile was correct for the others. Ordering a selection of the closest sizes gave me what I needed to properly seal the housing, with spares for next time...

Cheers,
Bill.
heraldcoupe is offline  
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Quote:
Originally Posted by heraldcoupe View Post
I couldn't get all of the right O-rings through Alfa. They have a smaller profile than the standard O-rings I keepd in the workshop, so I had a look online and found Exact Rubber Products. Good service with quick delivery.
There are three pipes to be sealed where they enter the thermostat housing, each needs two O-rings with each pair a different size. Some of the precise sizes are shown in the Electronic Parts Catalogue, but at least one of them wasn't. The cross section on each of the O-rings specified was 2.4 or 2.5mm, measuring the aperture in the housing against the locating grooves in the pipes confirmed this profile was correct for the others. Ordering a selection of the closest sizes gave me what I needed to properly seal the housing, with spares for next time...

Cheers,
Bill.
Thanks Bill. Thats very useful information as may need to do this in the near future.
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