Replace Thermostat Volvo 850, S70, V70, C70 or XC70
Overview
The thermostat is located between the engine and the radiator. The thermostat acts as a valve that stays closed during engine warm-up. When the thermostat is closed, it prevents coolant from leaving the engine and circulating through the radiator. When the engine gets warm, the thermostat’s spring valve opens, allowing coolant to circulate through the radiator to be cooled. If your Volvo is overheating (it failed closed) or the temperature needle is no longer reaching 3 o’clock (it failed open like mine), you need a new thermostat.
Tools
- ratchet and 10mm socket
- ramps or jack and
- jackstands to get the front of the car off the ground
- blocks for the rear wheels
- torx bit size T40, long
- WD-40
- bucket to collect coolant
- funnel
Procedure
Raise the front of the car using a jack and jackstands, or if you have ramps like me, with ramps. Put the transmission in Park, activate the parking brake, turn off the ignition, and block the rear wheels. If the temperature needle is anywhere but ‘cold,’ wait an hour so that the coolant is cools. Remove the big black plastic radiator splash guard (one bolt on each side, 10mm I believe) under the radiator. Remove the cap on the coolant reservoir, then place the bucket under the plastic radiator drain valve. This can be found on the driver’s side, bottom edge of the radiator. 
Drain about two liters of coolant into the bucket, then tighten the valve back up. Be very careful with this valve… it’s plastic and they have been known to break easily.
The next step is to loosen the two torx bolts that hold the thermostat housing together. Two things to note: spray some WD-40 or other loosening agent on the bolts, and, you may want to take off the aluminum fuel injector rail guard to get a better look at the hidden torx bolt. Ok, on to the details… One torx bolt is easy to get two… the other is, well, difficult. I got a torx bit and used that on an extender with a ratchet, but the bit was forced to contact the bolt at an angle that almost caused the bolt to get stipped. I’d strongly recommend getting a long torx bit like this. 
You don’t need to remove either of the hoses that connect the housing to the radiator and coolant reservior. With the torx bolts off, the top of the housing comes right off, as does the thermostat inside. Take it out and put the new one in. Put the top back on, tighten the torx bolts, and pour the coolant back into the coolant reservoir. Don’t forget to make sure the reservoir cap is put back on and the drain valve is tight. Put the splash guard back on and you’re ready to go.
Conclusion
Like I mentioned above, you can try to use a short bit to get the difficult torx bolt out, but my strong recommendation is to use a long one, or if you have the grip of Arnold Schwarzenegger, a T40 torxdriver. While you’re replacing the thermostat, you might as well replace the coolant also, flushing the system in between. I didn’t because I didn’t have any antifreeze with me, but I’m going to pick some up in a week or two.
Volvo Repair Details
17 Feb 2009Posted in Fluids, Lubricants, Additives & Sealers Radiator, Thermostat, Coolant, Antifreeze Volvo 850 Volvo S70 & V70, 1998-2000 Volvo XC70 & V70XC
Tags: replace thermostat, thermostat replacement tutorial
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The long T40 bit (a $15 investment) is a must!
1. Definitely use some W-D40 on the bolts wait about 4 min (get a beer).
2. Pop off the fuel rail.
3. Loosen the easy access bolt first then the harder to reach one.
4. Pull out old thermostat….replace with new. (replace bolts) then attach fuel rail
5. Fill the reserve and go.
Est. time 11 min. It’s that easy!
I had I similar problem but I found siphoning the coolant out to be very useful, very little mess and if you use a clean bucket the coolant can be reused (my coolant was only put in two days before so was worth saving), no jacking needed.
Siphon out the expansion tank, so you can release the top radiator hose then stuff the pipe down the inside of the rad to the bottom, and then drain the rad.
Pulling the coolant up a clear pipe (fish tank hose or wine making hose), till near the top, and then pinch off the pipe, and releasing when low down in a bucket saves getting a mouth full, best do this when the coolant is cold (obviously).
I also replaced my thermastat on an emergency basis. The t-stat stuck in the closed position and my car overheated. Here is my two bits:
1) I agree with the LONG torx driver bit. Otherwise there is a good chance of stripping the head.
2) Try a hand-held impact driver to loosen the two stubborn bolts.
3) It is possibe to drain the coolant without a ramp or a jack stand. Simply detach the lower radiator hose from the radiator. That way, no need to crawl under the car, no need to remove splash guard. No fear of damaging the plastic drain plug.
Agreed that you must use the long T40 bit, but you must also watch out for the following. I have also heard of the hidden torx getting seized and snapping making for a very very expensive thermostat change. Do the easy one first, and gauge the force required to loosen it, if the hidden one requires significantly more force before it moves you may want to do the following procedure to avoid snapping the bolt.
Get a very long and thin high speed drill bit, now this may sound crazy, but you need to actually drill a hole into the thermostat housing/cover just below the head of the hidden bolt to gain access to the shaft of the bolt so that you can introduce lubricant or penetrant to the area that is actually seized. This area is solid aluminum and you wont cause any damage as long as you are very careful not to drill into the actual bolt. Once the hole is done all you need is one of those red straw adapters to your choice of spay to lube the seized area before trying to loosen the bolt. Good Luck!
I know nothing about cars and replaced the thermostat with this advice within 20 minutes. Thanks a million to all contributors! 2009 Aug 7
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Good stuff. The long T-40 driver bit cost me $3 at my local tool house. S-K offers a nice socket style for $38, but I just grabbed the cheap hex bit with a c-wrench and called it good. PB blaster for 20 minutes and a few light taps with a punch got the bolts ready to come out with no drama. I found that I didn’t have to jack the car at all; just pulled off the splash guard and stuck an antifreeze bottle on its side with a funnel stabbed into it, used the plastic drain fitting with no problem. I pulled the small hose to the reservoir off, as it took some twisting to get the top part of the housing off. Easy fix; car warms up quickly now. Thanks, everyone!
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Didn’t need the long torx at all on my 2000 S70. The one torx is hard to get to because of the black plastic housing over the engine that covers the belts. It can be quickly moved out of the way by removing the two torx screws on the top and popping the clip on the side (30 seconds max). You can just move the cover a little and have full access to the hard to reach torx bolt.
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2000 V70 XC, I didn’t need the long torx as well and there was no need to remove the coolant, total of 8 min to change from start to finish.
2000 S70 non-turbo: Just replaced thermostat. I agree with Mike, removing timing belt cover is easy, and provides full access to rear bolt on thermostat cover. Did not need long T40 torx driver. The splash guard on the 2000 S70 has a hole (1.5 inch diameter) directly under the radiator tank drain (left side). No need to raise car. I was able to loosen the plastic drain plug (carefully) with a deep 14mm socket. With engine cool, loosen until coolant runs, into a clean pan. No need to remove plug completely. Drained about 1 liter. Gently re-tighten drain plug. This is an excellent post. Thanks!
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I appreciate this forum and the advice.I have an s40 and changed my thermostat in 20 minutes! The t40 torx was essential, on a s40 to replace the tstat it is easiest to take the timeing belt cover off, to do this you will need a smaller tork bit, possibly 25,i luckliy had one. Couldnt find the drain valve on bottom of car so when i took the old tstat out i let the remaining antifreeze fall out. I bought a new tstat,wd40, seal gasket (sold sepertly) and a t40 tork bit, $13.48 all together! Sure beats the dealership!!
Thanks a million
Another great post. Helped greatly. However, just as I was about to pop down to my local DIY store for the torx extension I realised with a little endeavour by simply attaching a vice grip to the top of the torx key (T-shaped without one lug) the two bolts were easily released. No special tools required. Not to say that if yours are ‘welded’ on it might be different, but just to show that it can be done. Thank you.
First, I have decided that I’m an idiot. Here’s why, I stripped the 2nd torx bolt head, then broke off the easy out that I drilled into the stuck bolt, then in a fit of idiocy I diconnedted the gas line and pulled out the fuel injector to try and get increased access to the bolt. The bolt is still stuck but now I’m wondering if I’ve completely screwed up the fuel injection. I live in a small town that only has one mechanic and he charges triple the average so I’m wondering before I take it to him to replace the thermostat if I can easily just put the fuel line and injectors back in or if there’s a certain procedure.
Hi i have volvo v70 it is overheating very high and its crack the head, so we change the dead and headgasket even we change termostat twice, but it still overheating, its made me very sad with all i have spend on it, now we showed it to mechanic he said again there isn a problem with the engine, please give me advice on this matter, it will be great if send me email on iraj20@hotmail.co.uk.
thanks
iraj
2001 V70 XC. Torx came out nicely. Didn’t need a long bit. Took a little brain power to get the splash guard off. It had 2 Torx & 2 bolts. Something was still holding it in place and they I finally saw I simply had to release pressure on a plactic piece with a long screwdtiver & it came out. Later I saw there was a hole already in it to gain access to the drain. Wife picked up the part while she was out running errands and darn if it wasn’t missing the gasket. Off to the store in a few. I hope this fixes it.
Thank you so much for this forum! My Husband and I just changed out the thermostat on our 2000 V70 XC AWD SE. Garage would have easily charged us $250 for a job that cost us $20.00 for the new thermostat and gasket. Had we had known that the timing belt cover screws were T30, not T40 like the thermostat, it would have taken 10 minutes for this job. Took an additional 30 minutes to run to Autozone for the tool. Thank you again everyone for the helpful and money-saving information!