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Discussion Starter · #1 · (Edited)
The symptoms

1. Coolant level drops from max to min (or less) at seemingly random times, regardless of drive time, distance, style, etc.
2. Coolant on the undercarriage, front passenger side. Oil filter, oil pan, engine cradle.
Auto part Engine Vehicle Automotive engine part


3. Puddle peeking out from the passenger/right side of the car.
Tire Automotive tire Floor Wheel Alloy wheel


Parts / tools:
  1. Thermostat kit (#15 in diagram) 31293698 for 2005+ Part number 31293700 for 2002-2004.
  2. Gasket 8636573 (#5 in diagram). This does not come with the kit.
  3. Your favorite coolant.
  4. T40 and T60 Torx bits. I found largest size in most kits was T50, so had to buy T60 separately - about $5-$7.
  5. Small hose clamp for approx. 1/2" or 12 mm diameter (approx size of my pinkie) hose.
  6. Basic metric sockets and wrenches.

Technology Electronic device
White Line Monochrome Black-and-white


Basic overall steps.
I would estimate a novice could complete it within an hour. It took me a while longer because of taking photos along the way.
1. Buy parts.
2. Drain coolant from radiator.
3. Remove serpentine belt from power steering pump pulley.
4. Remove power steering fluid hose bracket & pump.
5. Disconnect coolant hose from thermostat.
6. Remove thermostat
7. Replace thermostat and gasket.

End of post. Forum only allows 5 images per post.
 

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This is very well done and should be added to the modification & repair sticky.
 

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Nice writeup. But I would have used a new oetiker clamp for the pcv/coolant/thermostat hose. 17mm.



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Yea this is really nice. Your engine bay is pretty clean might I add
 

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So what did you use for a gasket between the upper and lower housings?
Please see the 2nd photo in the DIY link: the gasket is part of the assembly.

So basically took tstat assmbly apart and used the following items:
1. Tstat itself
2. ECT sensor since "I am there" and may as well replaced the ECT sensor.
3. The gasket between Upper and Lower housings.
4. The Upper Housing.

Items #1-#3 are essential.
Item #4 is optional, you can re-use it.

But since the tstat is sold as an assembly, you may as well use new parts as much as possible.

If you follow my DIY to the "t", you can do the whole thing in 30 minutes, no need to mess with PS Pump bracket etc.

PS: I also have a 1998 Volvo S70 GLT with 185K miles, both Upper and Lower Tstat Housings are still original, zero issues.
 

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Great write-up. Just did this on my 2004 V70 Turbo AWD. I looked at just replacing the thermostat (not the housing) but determined I could not get proper fitment of the thermostat within the housing - besides it seemed ghetto to take apart a new housing just for the thermo and slap it in the old housing. Mostly I dreaded the lower torx bolt on the housing unit - its down in there and difficult to eyeball for threading. It was not as bad as it looked and/or I got lucky (the electrical tape trick could be a lifesaver, you dont want to drop that bolt or your torx driver into the abyss).

As to the oetiker clamp on the small hose - if you replace it with another oetiker clamp you will need a tool that can close it at a 90 degree angle as you cannot get at it from the top (way most tools close these - straight on). Bright lighting or even a headlamp are recommended as you are working in dark crevasses. Make sure you get a new seal with the new thermostat housing, mine didnt come bundled. You do not need to drain all the coolant I drained around 2 liters and it was below the thermo. By all means change your coolant frequently though as I have seen the radiator fail at the transmission and mix tranny fluid with coolant fluid :O

Finally a word of caution - the plastic handle on the dipstick is nestled right next to the coolant hose. Its difficult to see from the angle you take to do this job. I pushed too hard on the hose squeezing a ratchet in there and snapped off the head of my dipstick. Bummer but for the moment I drilled a small hole in the plastic end and used a screw to extract the dipstick. Got glue on it till the replacement comes in the mail...
 

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Thanks for all the tips. I've been avoiding this particular job. At one point I had the thermostat changed in conjunction with a timing belt job in the shop, Gone are the days of the simple thermostat swap that you could do blindfolded like on the 240 and S70....
 

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Additional Info

Great write up!

I had to do this yesterday after after years of trying to figure out where my coolant was going. Nothing was visible except an occasional drip spot on my garage floor once every so often. Then last summer I had to top off my coolant. Again I looked for a leak and had Volvo check it out only to find nothing. Then a few weeks ago my coolant was low again so I topped off and rechecked for a leak and found nothing again. I knew it was going somewhere but just couldn't find the leak. Finally, a few days after the last top-off, my coolant light came on again! This time there was a small puddle and I could see coolant on the bottom of the engine. I began trying to find where the leak was and squeezed the coolant line to the radiator and heard a squeal but couldn't pinpoint where it was coming from. I then did the old soapy water trick and found the leak to be at the thermostat (#17 in the diagram). Rather than just change the seal I opted to R2 the entire assembly. I was able to get it knocked out in under 1.5 hours, topped off the coolant and all is well again! No leaks!

If I could suggest a few additions to the write-up that might help others...

1) I would add a symptom that I had which is a tiny drip spot under the car that was always dry to the touch and I could never see happening... always in the same area towards the rear right of the oil pan. I knew something over time was leaving a spot on my garage floor but I guess after it dripped it dried so by the time I saw it I could never determine what it was.

2) I would also add the torque specs for the the two T40 M8 housing bolts which according to the Volvo torque specs and my local Volvo tech is 24 Nm or 17.70 Ft-Lbs. In researching this info I found all kinds of horror stories of people stripping out the heads of the screws, the engine block and even snapping Torx drivers in half.

3) Finally, I would add that it's important to clean any debris on the engine after removal of the old thermostat before installing the new gasket (#5 in the diagram) and thermostat assembly to ensure a good clean seal.

Your write-up was key and made this a fairly simple task so thanks so much for taking the time to post!
 

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Can anyone tell me if the thermostat for a 2001-04 S60 will work on a 2005-07 S60R?
I'm trying to replace the thermostat, without spending the money to buy an entire housing assembly.
 

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Just read through this, great writeup! This would've saved me a lot of money if I saw it back when my thermostat failed!
 

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If it's just leaking and not a bad tstat, you can also do it cheaper/easier if you so choose. My thermostat was fine, it was just the gasket in between the 2 halves of the housing that was leaking. I split it apart (left the base in the car, so no need to removed the steering pump), removed the old gasket, cleaning the surfaces, and resealed with coolant safe RTV. Reassembly is mildly frustrating (getting everything lined up and staying in place), but it cost less than $5 and took less than an hour.
 

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I was able to remove mine without taking the power steering pump off. A good T40 on a straight extension fits right under it just make sure it is properly seated in the torx head, I replaced the whole unit not just the thermostat itself. When you reinstall it, put the gasket on the housing with the bolts and put your torx on the bottom bolt and push it in so you don't lose it.

Another tip to save you headache later is when you get the new unit on there, get a screwdriver or pry bar and push the bottom of the housing towards the belts while tightening the T40s. if you don't do that, it will be impossible to get to the far left 10mm bolt on the intake manifold incase you need to do PCV or something down the road, you'd have to remove the thermostat housing if you don't. There's barely any room there for the skinniest 10mm socket you have and it's impossible to get a crowsfoot or wrench on it because the housing is so close to the head of the bolt.

I had to loosen my new housing and push it to the left and retighten, it hasn't leaked since I loosened it so well see but otherwise there was no way to get to the farthest left intake mani bolt.
 

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Sometime between July 2019 and today, the photos in this write up have been blurred out by photobucket.

I'm revisiting this job because the (new) OEM tstat I installed is stuck open. Good thing it's still under warranty. Would be nice to see all the photos again in case I've forgotten anything.

I'll probably be fine... Everything's fine...
 

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