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

[matthew1]

Great writeup, Zeeko. I made your account MVS Contributor level. I'll put this in the Volvo Repair Database.

[oragex]

I think it was an industry trend, if I remember BMW along others perhaps also went the same way at about the same year.. hard to follow their logic indeed especially since the coolant temp sensor seems to last much longer

[cn90]

I can understand the industry, simply b/c they do not want the customer to return (less satisfaction, thus their rating), affecting their brand name...but...

- My 1998 S70: tstat failed at 80K (open all the time, thus no heat in cabin), at 100K, the ECT went south.

- I think there is logic both ways:
1. Fix only what is broken to save money <--- DIYers do it this way.
2. "Shotgun" approach: fix them all to save time and prevent "call back" <--- Dealers do it this way.

[Zeeko]

Great writeup, Zeeko. I made your account MVS Contributor level. I'll put this in the Volvo Repair Database.

Thanks Matthew! Hope to contribute more in the future. And thanks for taking the time to edit those photos in where they needed to go- it looks great!

[atikovi]

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.

What is the connection? I never heard a cool running engine would fry a cat.

[abscate]

If the engine thinks it is cold it will inject more fuel for cold running. This excess fuel can make it back to the cat and burn there instead of the engine, which cooks the cat.

[atikovi]

If the engine thinks it is cold it will inject more fuel for cold running. This excess fuel can make it back to the cat and burn there instead of the engine, which cooks the cat.

First off, it injects more fuel for cold STARTING, not so much for cold running, at least not for a significant period of time, however, even if during that time excess fuel can make it back to the cat, there is problem with the ignition system. Otherwise, every car that operates in the 5-10 minute warm up phase would have fried cats. And second, I wouldn't consider 70C cold running by any means.

[abscate]

If the engine thinks it is cold it will inject more fuel for cold running. This excess fuel can make it back to the cat and burn there instead of the engine, which cooks the cat.

First off, it injects more fuel for cold STARTING, not so much for cold running, at least not for a significant period of time, however, even if during that time excess fuel can make it back to the cat, there is problem with the ignition system. Otherwise, every car that operates in the 5-10 minute warm up phase would have fried cats. And second, I wouldn't consider 70C cold running by any means.

I've measure the cold start time and monitored injection length for 10 minutes. It was about 3x normal warm idle and took ten minutes to reach steady state.

I do not know if the ECT reports cold temperatures, the ECM lengthens the injection time again, agreed.

On Denso cars , at least, the cold time is shortened by a high idle of 1500 rpm, and CVVT intake blows excess air into the manifold to heat up the cat fast and consume cold start fuel, so they engineered this thing well.

[darter99]

Thanks Zeeko, I used your guide and all went well. I have a 2006 V70 T5. The full assembly cost about $100 including the temperature sensor and the gasket (everything needed). To remove the lower T40 I could reach it with a long wobble extension and T40 bit that is about 1 1/2 inches long. It was a close call because the contour of the housing itself makes it difficult to squeeze that bit in due to the form of that bit. However, I later ordered a long T40 bit (maybe 7 inches) and that easily fits since the 'socket' part of this tool is not close to the T40 bolt. So I advise getting a long bit if possible. Also, I used a round magnet set in a rubber tube to 'grab' that lower bolt. The magnetic pull allowed me to sorta feel what was going on since I couldn't see what was happening. This made it easy to replace that bolt and feel when the threads caught. From reading the other replies I think there may be apples and oranges in this thread. With your car and mine it looks like the replacement of the full assembly is required. There is no 'replacing only the upper half' option unless one wishes to tempt fate by splitting a new part in half. Also when I replaced the full unit I did so with the sensor removed and then the tool needed (I think) was a deep socket 19mm to replace the sensor. This was easy. At no time did I use any gasket sealant and I hope that is the correct procedure. I wasn't really sure about that. It seems to be sealed up just fine. Thanks for your write-up. One last thing: it might appear that the full part (minus sensor) cannot possibly fit in but with the rotation you mention (and no force by the way) there is a perfect spot where it does drop in. Yea, on a dare I could now do this in 30 minutes if all the parts were in place. Maybe 15 minutes actually. But I took my time studying the puzzle so it was a couple of hours for me. Also, none of my bolts were 'stuck' so maybe I got lucky. Also, I drained 3/4 gallon of fluid before working and there was no spillage to deal with. Oh, last point: to locate this leak I could see green crystalline matter at the base of the assembly. Then I fashioned a pressure tester from a reservoir cap and a presta-type bicycle valve from an old bike tube. (Free from bike shop). This worked perfectly and after a few pumps I could see a fine mist spraying from between the two halves of the thermostat housing.

[cn90]

- Working on a 2007 S60 with 115K miles, some tricks for people...

1. If you replace the entire thermostat housing, then you may as well do the PCV mini-overhaul at 115K miles
bc you have access to that infamous right lower 10-mm bolt holding the intake manifold.

Even with thermostat in place, you can access that bolt but with great difficulty: trick...insert the 10-mm socket
(1/4-inch type), then use a wobble extension. Or you can cut the 10-mm down a bit to fit that tight place.
Just dumb engineering to start with anyway.

2. The key to that thermostat lower bolt that attaches to the engine block:
- Buy the Autozone Torx set (GreatNeck TQS15 or Surebilt set, same thing).
The T30 key has the correct length, but here is the trick" use the T30 bit with a 10-mm wrench, not with the socket supplied with the set.

Don't forget to spray the bolts with some PB Blaster one week beforehand.

I wrote a DIY a few yrs ago:

DIY: 2004 V70 2.5T PCV Job, a Brief Job (110K miles)
https://www.matthewsvolvosite.com/forum ... hp?t=91596


Anyway, this is the Torx set that will make the thermostat job much easier. In fact, when you use this Torx set,
there is no need to remove the PS Pump at all.

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