Thermostat housing issues

toddao · Post by **toddao** » Thu Dec 11, 2008 8:16 pm

As I've just done the head gasket on the TRD I'm now overhauling the cooling system to make sure there's no repeats.

I wanted to test the thermostat but trying to access it, the heads of two of the bolts holding the cover sheared off - completely rusted in.
I took the whole thing off, put it in a vice and tried to drill out the bolts. I made a right pigs ear of this. I've got a stand for the drill but it was too awkward to line up and the drill wandered into the alu casing.. oops. I just don't have the technology.

What would be the correct way to remove these bolts? Pillar drill? Would I then have to use a tap to make new threads?

Seems the cover is still available from Citroen ( heaven knows how much?) but I want to try to reclaim the other part of the housing - the outlet tank - so I need to get the bolts out still which have been there since 1985!

I'm racing to get to the TÜV ( MOT) next week and it's pretty uphill we're heavy under snow so it's f-f-f-f-f-f-r-r-rr-eezing in the barn and the wife's getting anxious that we won't have a car once the yellow one goes off the road.. v.soon.

DavidRutherford · Post by **DavidRutherford** » Thu Dec 11, 2008 8:28 pm

There's no right way to do this, although my preferred method is:

Drill out the old bolts as best you can. This can be very difficult, and I often find the best thing to do is to drill from both sides, trying to line up as best you can.

Drill the holes in the casing out to 8mm diameter, and the backing bit to 6.8mm. Now tap an M8 thread in the backing, and use M8 bolts to hold the cover on. Use far too much coppergrease in the vain hope that it might come apart again in the future.

Post by **mat_fenwick** » Thu Dec 11, 2008 10:05 pm

^^^What he said, but I would suggest using high tensile bolts (stamped with 12.8 or 8.8 on the head), that will hopefully resist snapping in the future. Mind you, it's going to take more torque to shear off an M8 bolt anyway...
Also, if you can, it might be worth trying to mark the centre of the sheared off bolt with a punch, that way the drill stands more chance of starting off in the centre.

ken newbold · Post by **ken newbold** » Thu Dec 11, 2008 10:48 pm

Which type of casing is it?

jonathan_dyane · Post by **jonathan_dyane** » Thu Dec 11, 2008 11:47 pm

My car also has the early type thermostat housing, and the extended warm up and poor heater does suggest a stuck thermostat, which the temperature gauge I am shortly to fit will likely confirm.

Given that replacing the 'stat usually involves shearing the housing bolts, I had thought that if (when) this happens in my case, I would get a housing from a later XUD engine and retrofit that (the one with the plastic top hose outlet and integral diesel filter).

I'm sure others will comment on the wisdom or otherwise of this plan, and should there be no obstacles this may be an easy and quick solution.

toddao · Post by **toddao** » Fri Dec 12, 2008 8:36 am

Thanks for replies everyone. Ken wrote

Which type of casing is it?

I don't know - just the early 1.9 D type? I'm going to see Herr Wolf at the Citroen/Ferrari dealer now to see what he can find there in the storeroom before I start making even bigger holes. He's got a few things lying about. Will update later.

jeremy · Post by **jeremy** » Fri Dec 12, 2008 9:52 am

I had to do those on my DTR Turbo some years ago. I think 2 bolts came out and 2 sheared - I was able to drill them in situ and think I was able to replace with M6 nuts and bolts as the holes went through and I could fit a nut on the back.

MULLEY · Post by **MULLEY** » Fri Dec 12, 2008 1:17 pm

How come they always sheer off? is it just corrosion over time?

jonathan_dyane · Post by **jonathan_dyane** » Fri Dec 12, 2008 1:27 pm

MULLEY wrote:How come they always sheer off? is it just corrosion over time?

Exactly that, particularly as the bolts go through the waterway (AFAIR) and so if coolant is neglected they rot, particularly the lower two bolts.

The later cars with the plastic diesel filter on top of the thermostat housing don't seem to suffer this, as they have a different set up where the coolant cannot contact the bolts which retain the (now plastic) combined top hose outlet/thermostat cover.

(I have no idea what the set up on the petrol cars is like).

toddao · Post by **toddao** » Fri Dec 12, 2008 2:16 pm

I managed to get the cover, so I'm hoping that I can drill out the bolts on the tank now. Though judging by the state of the cover ones, the holes won't be easy, and they'll be larger than the 7mm bolts that go through the cover..

Jeremy, you did very well to drill them out cleanly, let alone in situ. Maybe the bit that I'm using isn't hard enough?

I found out while I was by Citroen this morning ( the parts store was full of recently arrived wooden crates from Crewe.. ) that the necessary thermostat will be discontinued in Germany after tomorrow! Having said that, there wasn't one available. Very kindly they phoned round and found one in the extreme north of Germany, in Flensburg, on the North Sea coast ( about as far away as you can go from here) which will be here on Monday.

jeremy · Post by **jeremy** » Fri Dec 12, 2008 8:32 pm

Ah yes the thermostat - my local Citroen dealer was quoting me £14 or so for what seemed to be the gasket alone so I went to my friendly accessory shop to see if he could help - and he had one on the shelf! (the huge one).

Wanted one for a 1600 1951 Land Rover - same shop - guy reeled off the no and got it off the shelf!

The shop supplies Quinton Hazell bits which seem OK. QH catalogues can be downloaded here:

http://www2.qha.com/catalogues.asp

toddao · Post by **toddao** » Fri Dec 12, 2008 9:29 pm

Sounds as though you've got a good local shop there Jeremy!

But today, after they had gone to so much trouble phoning various Citroen dealerships I decided to order it for €22 which is not bad considering that it's travelling over a thousand kms to be here!

I have now been given the contact to a very good Citroen parts service here in Germany that sells generic parts and is run by enthusiastic people. They sell a water pump for €35 as opposed to Citroen's €120!

Another question re the thermostat housing - is that silicon or what that seals in the fast idle sensor? I've got to seal it into the new cover

jonathan_dyane · Post by **jonathan_dyane** » Fri Dec 12, 2008 11:22 pm

toddao wrote: Another question re the thermostat housing - is that silicon or what that seals in the fast idle sensor? I've got to seal it into the new cover

IIRC there would originally have been a copper washer 'twixt the sensor and the housing; perhaps this has been supplemented with silicone, or perhaps it has been lost. If it does still exist, I would soften it by heating it with a gas torch/the ring on my cooker and dropping it into cold water, then refit it sans silicone.

jeremy · Post by **jeremy** » Sat Dec 13, 2008 6:28 am

I think its a copper washer. I think when I replaced the DTR Turbo one many years ago there was a rubber type 'O' ring on the one I removed.

DavidRutherford · Post by **DavidRutherford** » Sat Dec 13, 2008 8:44 am

Even if you have either a copper washer or a rubber O-ring, some PTFE tape on the threads would be a worthwile precaution against leaks. I did this on one that leaked like a sieve, and it never leaked again.