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Discussion Starter · #1 ·
There's not a lot of action on the S80 page, and mine is an 06 with the 2.5 5-cyl turbo so I thought I'd put it here for some more eyeballs...

I bought a 2006 S80 in December that I've yet to register. Kind of dreading DMV in CT right now if you've heard about our problems, so I've contented myself to tinker with my new toy in the garage. When I test drove the car (private owner) I saw/smelled coolant from the passenger side of the engine. Figured it was the water pump, knocked almost $1000 off the price for that and bought the car.

It's not the water pump.

At first I thought I'd found the culprit in the thermostat housing gasket where it connects to the cylinder head. I'd put a shop rag in there and come back the next day to find coolant. Bought the gasket at the dealer for $10, replaced the upper and lower hoses while I was there, and did a coolant flush and buttoned it up. Problem solved.

Walking into the garage today, I saw coolant on the floor in the same spot as before. It's not residual, I washed the underbody tray before I reinstalled it and wiped everything down. It drips off the frame rail and the oil filter housing. The overflow tank looks fine, and it's on the other side of the belts so I doubt that is the problem. It's too far back to be the radiator. The water pump is dry. Kinda baffled here.

Any and all opinions welcomed.

TIA.
 

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Discussion Starter · #3 · (Edited)
Thanks Slash -

However I don't know what that's going to show as it's dripping and I haven't driven the car in a month.

Advance Auto has the pressure testers to borrow so I'm getting one at lunch. Going to remove the under tray, drain a gallon, mix in the dye and add it back and let the car run until the thermostat opens and circulates it everywhere. Shut it off, let it cool and then pressurize and start looking.... my fear is that it's the head gasket but I can't find the source. If it is the head, I suspect the leak us at the end of the passengers side and is hidden by half of the plastic cover that remains when you remove the other half to do the timing belt.

If it's the head gasket, I'm tempted to try a 'fix in a bottle' before I go through the ordeal of removing the head. I'm getting no blow-by into the coolant, it's perfectly clean so any leak is strictly water jacket to atmosphere....
 

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There is also coolant running from the lower thermostat housing to the pcv system. Could also be coming from the rear of the block, there is a water pipe in the back the has a paper gasket, the also supplies the turbo with coolant and those lines are also susceptible to leaking, as are the oil cooler lines.
 

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Discussion Starter · #6 ·
The overflow tanks are known to crack from age, so I would still expect that to be the case for you....
It's a cheap replacement and advisable to do anyways so if I were you I'd do it now and see if it's fixed. If not fixed, continue the search ;-).
I had that out, it looks in good shape and if it were to leak I would find coolant coming down that side of the frame but it's a good 4 inches over the belts to the ending block....
 

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Discussion Starter · #7 ·
Pumped it up to 15 psi last night ... it dropped less than 1 psi over two hours. I stuck a borescope in there and around the accessory mounting bracket and the serpentine tensioner it's wet. So tight in there that even the borescope I can't see well. Took off the passenger wheel and pulled back the fender line....But there is nothing else in that area except the head gasket, or I'm missing something. Unless it's the thermostat housing and it's migrating. Not where it meets the cylinder head, but the two halves of the housing itself.
 

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Pumped it up to 15 psi last night ... it dropped less than 1 psi over two hours. I stuck a borescope in there and around the accessory mounting bracket and the serpentine tensioner it's wet. So tight in there that even the borescope I can't see well. Took off the passenger wheel and pulled back the fender line....But there is nothing else in that area except the head gasket, or I'm missing something. Unless it's the thermostat housing and it's migrating. Not where it meets the cylinder head, but the two halves of the housing itself.
Could be the housing to the head (paper gasket), or the thermostat upper and lower half (rubber ring around the thermostat).
 

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Discussion Starter · #9 ·
Could be the housing to the head (paper gasket), or the thermostat upper and lower half (rubber ring around the thermostat).
Hoping it's the gasket between the two halves of the thermostat but I'm not optimistic. I already replaced the gasket between the thermostat and the cylinder head. I just added an ounce of dye to the coolant and shot a can of brake cleaner at the area to clean it up before I run the engine. Waiting for the fumes to die down lol.
 

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Discussion Starter · #10 ·
It was the can of brake cleaner I shot over that side of the engine that did the trick... once the gunk was out of the way, the source of the leak became apparent..

It's the gasket between the two halves of the thermostat housing:



That's not sold as a spare, you need the entire $120 thermostat housing. Tempted to break it down and just shoot Form-A-Gasket in there.

So glad it's not the head gasket lol. :)

Many thanks to all who replied.
 
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