V50 General : Thermostat replacement

[PeteTheSwede]

Hello.

I have looked through the forum to try to find any specific information in regards to the thermostat housing, but havent found anything I'm looking for, so,what is the best action to replace the thermostat on the 1.8 petrol engine?

I know the thermostat is stuck, as temp goes to the middle at idle but drops one or two marks while driving...

I've got myself a Mhale/Behr thermostat from, and was going to replace it today but turns out the impossible bolt (hidden bolt number 3) was defect and I could not get that one out. *Therefore had to put everything back again to my annoyance.

So here goes, is it possible to break the plastic housing to try to get access and try to rid of the old broken bolt or do I have to remove the whole intake manifold?

The car is a 55 plate, so a 2006 model, full service history but hasn't been used much, currently the car has 74K on the clock and used daily now, however everything works perfect, well except the thermostat.

Thank you in advance,

[SnackBox]

It can be done without having to remove the manifold, you'll defiantly have to remove the aux belt though.

[Thassos]

Hi pete,

Sounds like you have the mazda engine there, i recall a similar struggle to get the 3rd bolt out when needing to replace the thermostat on a 2007 2L petrol, as you say i dont think you can even see the bolt head (is it 8mm ?) you probably need a 1/4 " drive ratchet with an extension and or universal joint or wobble bar extension as i recall you cant get straight access to the bolt, those bendy extensions that look a bit like a pipe bending spring might also be worth a try... yes its a total fiddle, but with the right tool combination and a lot of cursing it can be done 😁

The housing is an all plastic affair, with a large and small hose take off if i recall, and it does seem to be a common failure on those engines, can also lead to excessive oil consumption esp in cold weather as the engine never gets up to temp. At least when you get it swapped you should find your heater system works a lot better, but keep an eye on the oil until then..

[Thassos]

Interestingly dr haynes says remove the inlet manifold, but that is a lot more work, i wonder what vida suggests ?

I seem to recall removing the headlamp on that side gives you a bit better view/access also

Hope thats of some help, sometimes it just needs an alternative approach to get the impossible done 😀

[PeteTheSwede]

Originally Posted by Thassos

Interestingly dr haynes says remove the inlet manifold, but that is a lot more work, i wonder what vida suggests ?

I seem to recall removing the headlamp on that side gives you a bit better view/access also

Hope thats of some help, sometimes it just needs an alternative approach to get the impossible done 😀

Thank you Thassos.
You are indeed correct, it's an 8mm socket needed but by the look of it, when I tried to remove the "invisible" screw, I noticed someone have had a go at it at some point and by doing so, rounded the head on that ¤%&# screw!!

VIDA, believe it or not, suggest access without removing the inlet manifold by using the space between the manifold and the belt tensioner. of you're a toddles with wee hands it might work but with hands the size of barn doors it aint easy at all!! hahaha

I opted for the VIDA suggestion, I still found it to narrow a space, so removed the tensioner, a 17mm to slacken the belt, and a 10mm socket to remove the 3 screews holding the tensioner. I also removed the wee connector for the fuelrail/ injectors and that gave enough space to work... Tried to lamp suggestion but didn't seem to do much but will try next time.

To be on the safe side, I remove the battery negative connector, so I could disconnect anything i needed without risking damaging the ecu or whatever are in these cars today.

So my follow up question is this: do you think it is possible to use a hack saw to simply cut the pipes off on the housing, cut it to pieces to gain better access to be able to remove the damaged screw?

Regards,
Peter

[PeteTheSwede]

Originally Posted by SnackBox

It can be done without having to remove the manifold, you'll defiantly have to remove the aux belt though.

Yeah, I removed the whole tensioner as it was as easy requiring only to remove 3 screws and loosen the belt.

Thank you

[Thassos]

Hmm the rounded off bolt, is going to make it pretty difficult to remove, one suggestion here would be to use a 8mm socket, then mix up some plastic steel putty, push it into the socket, then onto the rounded off bolt (problem being you may not even be able to see if its onto the head ok, use a hairdryer and warm it up a bit so it sets hard (pehaps leave some time) then see if you can unscrew it (if all goes well youll get it out, if the socket parts company with the bolt head then youre back where you were, problem might be as you unscrew the bolt there isnt sufficient clearance to get it out, so use a short socket maybe.. ) i used this idea once on a rounded off wheel security bolt, and it worked (of course you mess up the socket and bolt your trying to remove).

The stuff i used was quicsteel,

What sort of hose clips are on yours?, if they are the spring type they can be a pain to spring open in a tight space, ive got a tool with a cable that can work but usually theyre a pain..

Cutting the plastic housing might work if you have a dremel but suspect unless you have the manifold off access might be very difficult..

post some pics of what you have there..

[PeteTheSwede]

Originally Posted by Thassos

Hmm the rounded off bolt, is going to make it pretty difficult to remove, one suggestion here would be to use a 8mm socket, then mix up some plastic steel putty, push it into the socket, then onto the rounded off bolt (problem being you may not even be able to see if its onto the head ok, use a hairdryer and warm it up a bit so it sets hard (pehaps leave some time) then see if you can unscrew it (if all goes well youll get it out, if the socket parts company with the bolt head then youre back where you were, problem might be as you unscrew the bolt there isnt sufficient clearance to get it out, so use a short socket maybe.. ) i used this idea once on a rounded off wheel security bolt, and it worked (of course you mess up the socket and bolt your trying to remove).

The stuff i used was quicsteel,

What sort of hose clips are on yours?, if they are the spring type they can be a pain to spring open in a tight space, ive got a tool with a cable that can work but usually theyre a pain..

Cutting the plastic housing might work if you have a dremel but suspect unless you have the manifold off access might be very difficult..

post some pics of what you have there..

Now that is a good idea with the putty thing. I've used one of those things to sort out a water leak on a Rover 600 once and that fix never failed so will be worth a try.

I also have a wee Dremel thing from Lidl and it had loads of accessories which I actually sorted a broken headlight adjuster with (the Allan key adjuster snapped) so that is plan B.

Surprise surprise, I had a locknut failure and found a guy in Motherwell, "Nut Off". Took 2 mins and a tenner to sort..

The spring clips where a doddle to get off but one disappeared for ever. So now I'm using the normal screw ones.

Try the link and see if it works as I've never shared photos on forums before. If it works, this is the access with the tensioner removed and before doing any work..

https://1drv.ms/u/s!AmfC9HlSdRxflLha...ZgmVQ?e=nxVVYQ

[Thassos]

hi Pete,

The pic on onedrive works 😁

other way is just click on the paperclip, or manage attachments and upload directly here, (just make sure the pics are not super high res), i use a good free editor photoscape (you can resize them on there, before uploading)

Are you able to get a straight extension on the hidden 3rd bolt?, ive got a spare 1/4 " 100mm draper one if any use to you,

Rounded off bolts are a pig .. but there is usually a way with a bit of lateral thinking 😁

[Thassos]

hi pete,

did you ever get that 3rd bolt off ?, or the stat?