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How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo's stylish, distinctive "P2" platform cars.

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Zeeko
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How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by Zeeko » Mon Nov 20, 2017 10:44 pm

Hey all-

If you have a newer P2 Volvo that doesn't allow you to just pop the top off your housing and plunk in a new thermostat, you're in for a treat- if someone wants to specify exactly which Volvos require the full housing replacement, I'd be happy to edit that info itn. I didn't find very many tutorials on this process, so I thought I would share my experience- there were quite a few swear words involved and in my opinion, this job is a huge pain in the nuts, but I also did it in my driveway in 40 degrees in the dark after work in Minnesota.

For reference, my Volvo is a 2004 V70 2.5T Turbo with 160K on the clock. The previous owner had the CAT replaced at about 107K... I noticed the temp gauge would drop about 1/16" when driving on the highway- when I hooked up a bluetooth OBD tester, I saw that the temp was dropping into the mid 70's (C) on the freeway- not cool, and this is probably what fried the first CAT. So here goes:

What you need:

1. Coolant- I just grabbed a couple gallons of the Autozone stuff 50/50 that can mix with everything

2. The volvo thermostat housing and gasket. Replace the upper radiator hose while you're here. You may need 2 new clamps- i just reused mine.

3. If your car is like mine, you'll need an additional small hose (just get a foot of radiator hose) and 2 new small clamps to replace the annoyng volvo spring clamps. I actually ended up re-using the old hose as it was impossible to get the new hose to not kink.

4. Get about 1' of small diameter radiator hose anyway

5.
PB Blaster with that nice little plastic tube for precise aiming
a 13 mm wrench,
T25-T40 Torx bits that you can fit in a 1/4" socket. There are also T25-T40 torx bits that can fit on the end of a 1/4" and 1/2" drive ratchet- they sell a set at Autozone for 14$... very handy- buy them.
Have a 1/4" ratchet and a 1/2" ratchet handy and a variety of extensions (not the small one, but the ~8" one) and wobbles for each one..
A ryobi flexible screwdriver extension (it's about 1 FT long and it's a life saver).
A long magnet for retrieving dropped screws/torx bits.
Beefy pliers.
Rags.
A funnel.
A mop bucket your gf won't mind you using to catch coolant.
A headlamp.
Magnetic Screw holder- set it near the passenger side headlight where you can easily set screws/bits
Small fingers- if you have sausage fingers, you're going to be screwed.
Duct tape

The process - take a look at the very few photos I took and read through the whole thing before attempting this!:

Photo Link: https://imgur.com/a/G4AC9

With your car cold(!):

1. Jack up the car/put jack stands in, remove the belly pan- behind the engine block more on the pax side of the car is a petcock to release the coolant juices. Pop the wrench on and use the 1 ' of the small diameter radiator line to pop on the nipple and direct the stream of coolant into your bucket. PB blast the petcock before you touch it.

2. open up the coolant overflow cap so the juices can flow easily.

3. Use a torx to remove the 2 screws on that hold the timing belt cover in place- remove the cover and set aside.

4. After there's about a 1/2 gallon in the bucket, you should be good to go on removing the radiator hoses. I think you could let out as much coolant as you want, but I closed mine up at this point.

5. Unscrew the upper radiator hose on the radiator side as this is the easiest, then do your damndest to unlatch one of the volvo spring connectors that hold the small radiator tube in place- you just need to pull it off from either the thermostat housing or the intake manifold side. Don't wreck that little tube- you'll probably need it. Once you have one side off each hose, don't bother trying to get the likely impossible to remove the radiator hose clamp on the thermostat side.

6. PB Blast the 2 smaller torx screws that are holding in the easier-to-remove portion of the thermostat housing with the upper rad hose (and maybe the other one if you left that side attached) attached. Use the Ryobi or wobble bit with your torx and remove these screws- it should be a piece of cake. Pull this part out and any crap that comes out with it- the thermostat/gasket, etc. I hope you didn't destroy that little tube because you're going to need to re-use it.

7. At this point, you should be looking at the base of the thermostat housing and one big ass T40 torx screw that looks really easy to remove and you're scratching your head wondering how the hell you're going to get at the one you can't see on the bottom side. Get your headlamp out, and crouch low, if you move toward the driver side, you'll catch a glimpse of the worst screw in the world. Hit this screw with a little PB Blaster.
ujx5cbZ.jpg
1/2" ratchet, extension and T40 torx bit from autozone for REMOVING the lower screw on the housing base
PPZNke9.jpg
How I positioned the ratchet/extension to remove the lower screw
8. I recommend going for the lower screw first. Take a look at my photos. It's a huge PIA, however, i was able to use a 1/2" ratchet, extension, and a that T40 torx socket from autozone- no wobbles needed... I positioned it in place in front of the hard metal pipe near the power steering, and went straight in- at some point you'll get it into the right place and you'll be able to loosen it. When it gets close to coming out, take out the wrench and use just your fingers to ensure the screw doesn't drop. If you have big fat fingers, you WILL be screwed at this point- you might want to get your GF to help.

9. You got the bottom screw out- congrats- that wasn't even the hard part of this job. Now remove the upper screw.
nbMINju.jpg
it's out!
10. Ease the housing base out and remove the electrical connector at this point - i like being able to see what I'm doing with these connectors as they aren't intuitive on how to remove them. You just squeeze the grey part down and pull- this one works how you think it should.

11. Use a clean paper towel/rag and clean up the base.

12. Get your new thermostat / gasket and those 2 big ass screws ready and get ready to hate everything.

13. Now you're wondering- if we split the housing in half to remove it, how the hell are we going to put an entire assembled housing in that little hole between all of this hard metal stuff. See my photos- you need to put it into the pocket with the radiator hose side first, and then front flip it (towards the rear of the car) into place. While the gasket side is facing you- before you do the front flip, get your gasket, put it into place, grab one of the two T40 screws, very carefully put it through the (soon to be) bottom of the housing base, hold on to the screw so it doesn't fall out, and then put the top screw in through the housing/gasket. The reason for doing this, is its a huge pain in the ass to find the hold to put that lower screw in when you've already put the assembly in place (yeah, you think you can put the just top screw through the housing and gasket, screw it in slightly, and then get the bottom one in? Go for it).
UYu2hTm.jpg
This is how you put the new housing in the hole- make it do a front flip toward the rear of the car after getting it in this pocket.
g9rSJG5.jpg
14. While holding on to both screws on the threaded side ever so carefully, make the housing do a flip towards the rear of the car. Don't push the housing in yet, just gently get the top screw started, and then get your bottom screw started. It's a huge pain in the ass- maybe the biggest pain in the ass. I think this new housing was slightly larger than the old one, and using the 1/2" drive with the socket end torx bit was just too big to get the lower screw in place. What I ended up using was a 1/4" ratchet, the 8"ish extension, a 1/4" socket and a 1/4" nut driver with a T40 torx bit duct-taped in place so it didn't fall out of the nut driver. Don't laugh- it worked!!! You can take the ratchet off and just twist the extension between your fingers to get the lower screw started.

15. Tighten both screws down- not sure what the spec is, but don't overdo it. You got through the hard part.

16. Pick your poison at this point- I chose to put the upper rad hose on first- I put the thermostat housing side on first, then the rad side. Please position your screw clamps in a way that will be easy to remove in the future- I recommend pointing the screw toward your fuel injector area- I was able to weave my ryobi flex attachment through the injector area to get at the upper hose screw. Use some spit on the ends of the insides of the new hoses to get them to slide on easier.
3cnsK53.jpg
Use the Ryobi + Nut Driver and a Screw Driver to get your clamps tightened.
17. Use a new piece/or reuse the small radiator hose to connect the two smaller brass nipples- position the clamps in a way that you can get at them with your flexi-bit or maybe just a 1/4" ratchet+extension+wobble+7mm socket. You can do this.
bMs34A5.jpg
Weaving the Ryobi through the intake area - note how I have the new hose clamp positioned.
18. You DID IT! Congrats! Just take a look and make sure everything is nice and tight.

19. Connect the electrical connector back on your coolant sensor.

20. Put the timing cover back on/put your screws in.

21. it's pretty vague about how to burp/refill your coolant, but pour coolant in the reservoir until you hit the max and it stays at the max. You tightened that petcock, right?

22. This is a scary part- start up the car and keep an eye out for leaks. Turn the heat to max (not sure if this is important, but I did it).

23. I'm not sure if you can leave the cap off, but I did. It doesn't instantly turn scalding hot- just hang out there with your coolant and funnel and keep the level at max.

24. Let the car get up to temp and keep maintaining the coolant level... At some point you'll hit temp and it won't really need any more. Put the top back on and give it a little gas, and check the level.

25. If you feel like it's not sucking down any more coolant, tighten the cap, take all of your tools out of the engine bay and take it around the block.

26. Pop the hood, check for leaks and you'll probably need to add a little coolant. Do it. Then take it on a quick jaunt, check the coolant, and bam you're done- I took mine on the highway for a second and then topped off the coolant one more time. If you're obsessive like me, you'll check it about 5 more times.

My temperature went from 70's on the freeway to a consistent 85+.
Last edited by matthew1 on Thu Nov 23, 2017 11:03 am, edited 1 time in total.
Reason: Added images from imgur link, added tags

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by oragex » Tue Nov 21, 2017 7:32 am

Just a side note, the thermostat is rated 90C for both turbo and non turbo, I wonder why are you getting 85C? My obd shows rather a 93C.. what are others getting?


Refilling the coolant, I let the reservoir cap off, let the engine idle until the thermostat opens... easier to do in summer, I would strongly suggest not to drive the car at this point because when the thermostat will open, the reservoir will empty all of a sudden - you will get a low coolant message but if you don't pay attention you will be driving the car with missing coolant, not good for the engine. If you are doing this job outside in winter, keep the car parked and rev the engine until the thermostat opens and the reservoir gets empty. Then refill the reservoir to max and go your business - always keep an eye on the instrument display just in case. Once the car parked over night, in the morning check again the coolant level in the reservoir and top it up if needed.
Last edited by oragex on Tue Nov 21, 2017 8:26 am, edited 1 time in total.

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by Rattnalle » Tue Nov 21, 2017 7:48 am

Regarding filling the system up again turning the heat up inside does nothing since there is always a full flow through the heater core. The only thing you can do really is fill it up and go for a drive with a bottle of coolant. After a while when the thermostat opens you'll get a "coolant low" message and can fill the last bit up.

As for temperature I actually only measured mine before replacing the thermostat but it was in the high 60s or something in +5C. Fuel economy in the cold went up noticeably. I'll see if I can remember to check next time I hook the car up.

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by Zeeko » Tue Nov 21, 2017 5:36 pm

@oragex- I imagine the temp fluctuates quite a bit more when it's 30 degrees outside. In stop and go, my temp would be in the 90's, but the moment i went on the highway it would drop 10-15 degrees and stay there when the car is 'heated up'. Right now, I'm getting 85 minimum on the highway in 30 degree temp, which seems to be improvement.

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by Zeeko » Tue Nov 21, 2017 5:36 pm

@oragex- I imagine the temp fluctuates quite a bit more when it's 30 degrees outside. In stop and go, my temp would be in the 90's, but the moment i went on the highway it would drop 10-15 degrees and stay there when the car is 'heated up'. Right now, I'm getting 85 minimum on the highway in 30 degree temp, which seems to be improvement.

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by cn90 » Wed Nov 22, 2017 9:52 pm

Original poster Zeeko,

Nice instructions but you did not have to go through all of those stuff.
The tstat in the P2 can be done in 30 minutes max (including swapping the coolant temp sensor) if you leave the LOWER half of the tstat housing alone, in a way this is the approach done in the P80 (Volvo 850, S70, V70 series).

I just replaced the tstat and coolant temp sensor in my 2005 XC90 2.5T with 105K miles.
I wrote a detailed DIY below, if you follow my tricks, it is a simple job.

DIY: 2005 Volvo XC90 Thermostat + ECT without removing PS Pump
viewtopic.php?t=79031
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by Rattnalle » Wed Nov 22, 2017 11:03 pm

Having read the instructions from both OP and cn90 I have to say that both make it sound quite a bit more complicated than just removing the PS-pump and then replacing the entire housing.

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by cn90 » Wed Nov 22, 2017 11:04 pm

Not really, if you read my DIY carefully, the whole thing is done in 30 minutes. Very very simple if you learned from my mistake.

I will summarize my tricks as below. It is very simple:

1. D/C the Larger Rad Hose and Small hose.
Do NOT re-attach these hoses until the very end.

2. Remove the 2 Torx #30 bolts and the UPPER Housing.

3. Leave the LOWER Tstat housing alone, just clean the mating surface.

4. Swap ECT as in the DIY link.

5. Swap Tstat itself.
- Install gasket.
- Re-install the UPPER Housing slowly, making sure the tstat pin sits inside the UPPER Housing correctly.
Use a pick tool or small right-angle pliers if necessary to help guide the pin in place.

6. Re-install the Large and Small hoses.

7. Refill with coolant, test drive, let engine cool down. Add more coolant as necessary.
- Or the alternative (or quick and "lazy") way is to overfill the coolant to about 1.25 inches above MAX.
It will settle down to just a tad below MAX after a drive.
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2005 XC90 2.5T 110K+

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by oragex » Thu Nov 23, 2017 7:26 am

Rattnalle wrote:
Wed Nov 22, 2017 11:03 pm
Having read the instructions from both OP and cn90 I have to say that both make it sound quite a bit more complicated than just removing the PS-pump and then replacing the entire housing.
Even with the pump away, I did not had access to the lower torx bolt with my 3/8" torx socket. Plus these bolts are tight.

On the other side, I did toss the pump when splitting the housing open, removing the pump really isn't big deal assuming someone is experienced with releasing the tensioner and tossing the serpentine belt off the pump pulley.

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Re: How-to: Replacing the Thermostat Housing on a Newer P2 Without Touching the Power Steering

Post by cn90 » Thu Nov 23, 2017 10:32 am

I think Volvo went overboard with this replacement part, forcing people to replace the whole thing, which includes:
- LOWER Tstat Housing
- UPPER Tstat Housing
- Tstat itself
- ECT

I have a 1998 Volvo S70 GLT with 190K miles, the Tstat housing (both LOWER and UPPER) is original.
- I have replaced the Tstat (using Wahler brand at $15/each) twice.
- The ECT once.

So, if you follow the same principles of repair of the Volvo 850, S70, V70 (P80), then you simply swap tstat and the ECT and done. Save new the LOWER and UPPER Housing as a souvenir in the blue box etc. LOL...

If you do EXACTLY what I wrote above, the whole thing takes 30 minutes, no need to mess around with the PS Pump...
2004 V70 2.5T 100K+
2005 XC90 2.5T 110K+

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