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The dos and do nots of replacing a thermostat

8.6K views 41 replies 31 participants last post by  milowokie  
G
#1 ·
Hello all,

At the weekend I replaced the thermostat on my 156 Selespeed, and I thought I'd share some hints and tips, might be of use, might not.

My stat has been noticably poor at holding temps since my new rad went in. It cost in the region of £25 from Shop4parts, and the temp sender cost about £12 from EB spares.

The whole operation in steps.

1. Take off all the air intake piework from the filter to the throttle housing for ease of access. Replace any off the remaining clips with jubilee clips.

2. Stare at the ridiculus shape of the stat and the bolt positions for a bit.

3. Remove the largest of the pipes from the stat (the front one, which leads to the top of the rad.) Be aware that your feet will start to get wet soon.

4. Remove the very thin connection pipe which goes to the header tank.

5. Feel positive all is going well.

6. Try to remove the bottom hose, the one that will be a stupidly tight fit, use mainly brute force and ignorance.

7. Undo the final hose clip, for the final hose which goes directly backwards to the heater matrix. (Another wet foot moment)

8. Try and find a combination of 13mm socket and adaptor to give the correct length of about 7 cm needed to get a socket in to the gap to get at the securing bolts without having to remove the battery.

9. Decide that a standard 13mm socket, plus a 1/4 inch adaptor piece will give the correct distance. Remove bolts, wonder why the stat is still very firmly attatched to the head.

10. Yank the stat off the head. (Again, more wet foot action, it just keeps on coming)

11. Clean the mating surface thoroughly with carb cleaner and let dry, then wash again with water and dry.

12. Connect the back and top hoses with new jubilee clips. Bolt the stat into place.

13. Then and only then can you refit the bottom hose, which is the tightest fit, and the hardest position to access.

14. Fit the final hose.

15, Check all bolts and clips are tight.

16. Re-assemble the intake pipework, taking a moment to clean out any dust and cack in the intake tract.

17. Re-fill the header tank to the max line, and squeeze all the hoses a lot. wait for a gurgle or three.

18. Run the engine, and top up as needed as the car self-bleeds.

19. Replace the header tank cap and run it up to temperature.

20. Check for leaks and drips and do not be scared when the old coolant on the exhaust starts to smoke a lot.

The end. All is well. Go for a thrash in it. The temperature is now climbing to 90, then the stat opens and the temp sticks at just between the 9 and the centre line. Spot on.

Oh,

21. Check the coolant a couple of times and make sure it is topped up.

22. Go for a beer after rubbing savlon all over the miriad of minor abrasions, cuts and gouges caused by the old clips and sharp edges.

I thank you.

Andy
 
#5 ·
Reminds me of the "stat" change I did last year :lol:

Actually, I was suprised how easy it was to change :)
 
#9 ·
Hi Guys,

This thread was a great help, I changed the stat on my 1.8 t-spark today and the gauge is right back up where it should be. I used a small screwdriver to open the clips and pulled them off with a long nose pliars so I avoided any the cuts and scrapes. My other top tip for the bottom hose is when you have the rest of the hoses off, remove the two bolts holding the stat on, remove the stat and with the stat in one hand, grip the hosewith the other hand as close to the stat as possible and twist them in opposing directions. This freed mine and it was simple to pull it off after that.
 
#10 ·
Here's mine from 2005. I now have the 3 inch socket that would have done it...


Changed the thermostat today. All the hose clips without screw releases are a bugger. Armed with several replacement jubilee clips I attacked it. First the air cleaner trunking but there's a pipe tucked under the engine cover; so off with that. Removed the two looms that were in the way. Then on to the 4 pipes attached to the thermostat housing. 3 off but the forth is tucked under the main outlet to the radiator and impossible to get at. The lower of the two 13mm bolts holding on the housing is pointing at the gap between the radiator outlet and this 4th pipe. It needs a long socket or a short extension. My extension was too long and up against the battery. Resorted to a ring spanner down and 1000 turns! Having got the housing off it was easy to turn it so that I could remove the 4th pipe.

Compared the two housings and the new thermostat is much simpler. Changed over the temperature sender and mounted the (supplied) rubber gasket in the groove. All going very well until the final loom was pushed back - the retaining clip broke off. So just a push fit for now.

Ran it round watching the temp gauge. Quite different now. It was running around the 70c mark. Now rock solid splitting the 9 on 90c (85c?). The big difference is the way it warmed up. Several people on this site have said that when the thermostat opens a slug of cold takes the gauge down to 70c. Mine did the same when new but in its failed state just went up to 70c and hovered up and down the 70 mark. The new just slowly climbed to 90c (splitting the 9) and stayed there.

Maybe this is how it should be!
 
#16 ·
good luck. the diesels' a ***** to change:mad:
 
#18 ·
TIP ON HOSE REMOVAL (any type)

After removing hose clip, insert a very small screwdriver between the hose and housing. Spray WD40 up the side of the screwdriver blade. Remove screw driver and rotate hose. The WD helps break the seal/grip. Once rotated, piece of cake! Also good for removing handlebar grips from bikes etc

REMOVING CRIMPED HOSE CLAMPS

Insert flat screwdriver in clamp loop. Wiggle back and forth to loosen and open loop, then cut with (jewellers) tin snips.
 
#23 ·
Hi everyone,

I made a short guide with pics for replacing the thermostat on a TS GTV here. Maybe it can be of use for people with other models with the TS engine (I dont know how much access varies)...

If someone changes the thermostat and fancies taking pics and writing a few notes about how it went/tips let me know! Must be mostly 156 doing this?
 
#24 ·
Except you gloss over the lower fixing bolt. I found that a very short extension on a 13mm socket would be ideal (I used a 13mm ring with 1000s of small movements). The other point is that the 4th hose is tucked underneath and it is pointless trying to find a way to remove it before the housing is off. Once you have the housing off it's quite simple to twist it to get at the lower pipe and it's clip.
 
#28 ·
Invest in one of these tools for removing the air intake clips (see attachment)

The problem with jubilee clips is that it is easy to over tighten and split the air intake pipes ...
 

Attachments

#29 ·
a decent pair of pliers should do the trick. shame the temp still doesn't sit at 90 sort of fluctuates between the 70&90 (80ish?). could be the sensor playing up then. my next challenge the maf:rolleyes: