V70: Engine Replacing coolant thermostat V70 2010 2.4D

[Tatsfield]

Not that I currently need to do this mod but if it is done to avoid the huge job of replacing the failed original thermostat, can we rely on the failed stat being in the fully open position. It seems to me that a randomly malfunctioning original thermostat might interfere with the predictable running of the cooling system and thus have an effect on the running of the engine regardless of whether the alternative unit was fitted in another position. Am, I right or does the additional stat fully take over all coolant temperature regulation?

[Matt Simmo]

Most stats are purely mechanical, with the temp being taken direct from the engine coolant temp. A fully open or closed stat will obviously vary according to the time of year so its very unlikley it has a bearing on the engine map.

I find it odd that so many modern cars have these kinds of issue yet my older Monza and Carlton GSI still have the original thermostat installed.

[Accelebrate]

I went through the fun of this repair last week. Reggit's thread had some useful pointers, so thank you for that. I'd say it was probably a 6-7 hour job for me, split over a few days for sanity. It through up a few challenges which I'll detail below. On the plus side, although access is horrible it is all from the top, so at least you're not rolling around under the car.

I had the same issue with a rusty bolt under the battery tray...



Drilled out...



...and replaced with a stainless bolt...



One of the bolts holding the EGR exhaust to the EGR sheared off. I tried encouraging what was left out with heat, mole grips, manual impact drivers and left handed drill bits but it didn't want to shift.



I then remembered that I own a MIG welder, and welded a nut onto what was left of the bolt stud...









In a decision that I might regret I opted for an aftermarket thermostat. The aftermarket part was £45 delivered next day from Steve at Trust Car Parts (formerly known as Braydons). It's made by Pro Parts Sweden who have a bit of a mixed reputation for their Volvo and Saab parts, but Steve assured me that he'd sold quite a few of them without any reports of failure.

For anyone else doing this, the Volvo part number is 31368373, the Pro Parts number is 26438373.



It doesn't come with the somewhat flexible pipe that runs into the EGR. I had a similar issue as Reggit where the pipe didn't want to release from the EGR, but I didn't have the luxury of being able to cut it. I managed to get some silicone spray into the fitting and after about half an hour of wiggling it popped out.

In my case the seal on the original thermostat had perished so severely that it had detached and become wrapped up in the spring. The thermostat was completely bypassed as a result. I had briefly considered leaving it alone and fitting a secondary thermostat (a Rover PEM101020 looked like a good candidate) but with hindsight I'm pleased that I've removed the dodgy seal from the system. I'm not sure it'd do my water pump much good if it broke loose.





My car was running so cold on the motorway that it had started throwing P0116 codes. I decided to also swap the coolant temp sensor as access was easy whilst everything was apart and drained. I'm 99% sure that the code that it threw was because of the car over-cooling rather than a sensor issue, but in the unlikely event that there were multiple issues it seemed prudent for the £15 that a Febi sensor cost.



Reassembly was relatively straightforward, although getting the EGR back into position took some time. It took a few journeys for the coolant level to remain on maximum, but it did eventually and hasn't moved in the 350 miles since then. Coolant temps now sit at a constant 94-95c when monitored over OBD. I hope that's useful to anyone else foolish enough to attempt this.

[Moussey]

Quick update on the re-sited thermostat while I am on, 2 and a half years in and it's working perfectly, no issues. I would defo do this again. Just battling with a DPF pressure sensor,

[Tatsfield]

So can we assume that the original stat failed in the fully open position so as to have created a fully flowing system with no thermostat impeding flow so that when you inserted an alternatively sited unit it became the only thermostat capable of closing off flow? Your mod, which thankfully works for you, would not be successful if the originally sited unit was failed in the closed position or in any partial closed state which would impede flow that could not be restored by the mod.

So there are two observations to be made. Firstly, do Volvo design this unit to fail in the fully open position knowing that it may take some time for the owner to have the unit replaced. Secondly, if you can put in an easily accessible unit which works perfectly, why didn't Volvo design it that way to save everyone a lot of trouble. Can they be so wilfully stupid or worse, they want a complicated replacement to boost dealership profitability on otherwise reliable cars.

I was always taught that the thermostat, like the now extinct contact breaker, was a consumable part that needed changing routinely to maintain the engine in a good running state. That approach now applies to coolant temperature sensors. Volvo can hardly say that thermostats don't fail and consequently making them needlessly difficult to replace undermines their reputation as an engine designer.

Rant over!

[Moussey]

Absolutely right that the mod only works if the stat fails open, and if it suddenly pings closed then I am in the do do.

As regards the design and why its in such a ridiculous place, who knows, I suspect its down to cost or near the egr or maybe in that ridiculous place is a bit better in extreme environments, like a Dubai traffic jam or the arctic circle??

[Pidgeonpost]

Having read this thread I ran a Car Scanner check on the coolant temp on our V70 this morning. With an ambient temperature of about 17-18C, and at the end of a 10 mile run it never rose above 75-80C. Think I'll be lifting the bonnet to confirm where the stat is. It would be good to have the optimum running temperature for the winter.

[BigGreenThing]

Is it normal for the "optimum temperature" to swing around a degree or three depending on how hard you're driving and the outside weather conditions?

Using the OBD2 Car Scanner Pro app I have...I noticed that the temp can vary from around 84-85C to 88-89C. If I "push it" up hill - temp goes up a degree or two...if I'm "cruising lightly" down hill, temp eases back to 85C ish.

Is that normal thermostat behaviour?

I'm guessing if I had an old school temp gauge - I wouldn't even see and register the slight rises/lowering!!

Heat still comes out when I pop the heater on- so all good there!

[Pidgeonpost]

Originally Posted by BigGreenThing

Is it normal for the "optimum temperature" to swing around a degree or three depending on how hard you're driving and the outside weather conditions?

Using the OBD2 Car Scanner Pro app I have...I noticed that the temp can vary from around 84-85C to 88-89C. If I "push it" up hill - temp goes up a degree or two...if I'm "cruising lightly" down hill, temp eases back to 85C ish.

Is that normal thermostat behaviour?

I'm guessing if I had an old school temp gauge - I wouldn't even see and register the slight rises/lowering!!

Heat still comes out when I pop the heater on- so all good there!

I'd say it's pretty normal to see some fluctuation in the registered temperature as the cooling system readjusts to changes in driving styles and road conditions. This morning I left Car Scanner running while I made a 20 mile trip on A-roads and fast dual carriageways and was pleased to see the app registering 80-85C by the time I got there. Took quite a while to reach that which leaves me wondering if I have a lazy 'stat or whether it's just a big ol' lump of engine to warm up.