Oil Cooling Thermostat Removal

woodycaldercloggs · Post by **woodycaldercloggs** » 01 Jul 2018, 10:26

I have a 1998 V70 with leaking oil cooler lines.
I have ordered new oil cooling lines to do the replacement but forgot to order an oil cooler thermostat gasket.
(where I live it takes a week to get replacement parts)

Can anyone tell me if it is necessary to remove the thermostat to replace the lines or can I do it by keeping it in place because I don't have a new gasket ?

VolvoAffair · Post by **VolvoAffair** » 01 Jul 2018, 20:00

Yes, you will need to remove the lines...

Post by **scot850** » 02 Jul 2018, 09:42

You don't need to remove the thermostat to do the lines, but it does make the job a little more challenging as you have to undo a partially hidden Torx bolt that holds a small end plate at the end of the 2 engine cooling pipes.

Another reason I would consider removing the thermostat is if the pipes have sings of oil leaking at the joint with the thermostat. There are 'O'-ring seals on the end of the pipes and if the oil has been weeping, due to the temperature it forms a hard crust in the seat area of the 'O'-rings. The local Volvo dealer replaced these twice before declaring the problem was the pipes themselves were faulty. I bought new cooling lines only to find it was nearly impossible to fit the 'O'-rings in. So in the end I removed the thermostat housing and found the hardened oil sludge had been tearing the 'O'-rings when pushed home. As the thermostat is no longer available new, I very carefully scraped the crap out and then a gentle rub with fine wet/dry paper all was good.

Bottom line was pipes were fine, but mechanic was lazy and wrong diagnostic. I ended up fitting new lines for no reason but as they are a swine to fit I left the new ones on.

Another thing to watch for is the plate that holds the bottom of the pipes into the thermostat. Over time it bows outwards on the ends allowing the pipes to pull out slightly which is what caused the leak in the first place. Either flatten the plate or reverse it when re-fitting so it pulls the pipes fully home.

I thought I had pictures but can't find them now.

Neil.

Post by **scot850** » 02 Jul 2018, 14:13

Knew if I looked hard enough I would find the pictures:

: Damage to oil cooler lower o-rings

: Thermostat removed for inspection

: Burnt on oil residue

If you look carefully at the lower inner part of the oil line opening you can see (sorry for picture clarity) a black rough patch where the old oil had burned and baked. This had a rough surface so shoving new seals over this resulted in the condition of the 'O' rings in the first picture. This was after the 2nd set had been fitted at the dealer with the same result.

: Burnt on oil residue (2)

This was all caused originally by the lower pipes being able to move outward due to the locating plate having warped outward on the ends and allowing oil to get passed the old hardened seals.

Neil.