Thermostat replacement

Dollywobbler · Post by **Dollywobbler** » Sat Feb 04, 2012 12:23 pm

New stat has arrived for the BX, though disappointingly I think the fan switch that has also arrived is the wrong one - has three terminals but all in a straight line. Hmmm.

I'm a little disappointed that the thermostat hasn't got a fresh gasket with it - they usually seem to. Given that the chances of salvaging the existing gasket are roughly nil (in my experience!) so do I try and track down the right gasket or should I have a go at making one? Or will slapping blue sealant everywhere be more/less successful?

It's currently raining, so I've got a fair bit of thinking time on this one!

Mothman · Post by **Mothman** » Sat Feb 04, 2012 12:37 pm

Ian,

i just used blue sealant and it worked fine.

Andy

Dollywobbler · Post by **Dollywobbler** » Sat Feb 04, 2012 12:55 pm

Thanks Andy. Must have a go at fitting the temp gauge I bought a while back as well. Especially if the cooling fan isn't kicking in! For now, I'm staying firmly indoors. Bloomin' weather.

Post by **Defender110** » Sat Feb 04, 2012 1:18 pm

Blue Hylomar is fantastic stuff, sold under licence fron Rolls Royce and IME never fails. I was once told RR has said you could use it as a head gasket if required butthis is not a theory I have ever or would be willing to test. Perfect for a little old thermostat though.

Dollywobbler · Post by **Dollywobbler** » Sun Feb 05, 2012 1:18 pm

That was a tricky job. Took the car for a run before I began, as in my experience, it avoids bolts shearing. Success again, though I also gave each bolt a good wallop with a hammer before undoing as well.

Came off nicely but good grief was it a mess inside! The thermostat had fallen apart and the interior lining of the 'stat housing looked like one of those mineral caves. Absolutely horrific. I'll get some pics up later.

Cleared out the gunk as best I could, then had a hell of a job trying to get the circlip out. Had to scrape an awful lot of gunk away, and use copious amounts of penetrating oil before I could get it to even move. My new circlip pliers proved entirely not up to the task, but thankfully a pair of long nosed pliers did the job.

New stat isn't quite right I don't think. It can move about beneath the circlip. It's the right size, but doesn't seem to have a thick edge like the one that came out. Thought I might as well fit it anyway and see if it works.

Slathered a load of copper grease over the bolts and ended up having to use silicon sealant as my Blue has gone missing. Bled the system and joy of joys, the top hose wasn't getting warm. The 'stat was doing its job. Kept my hand on it and it suddenly warmed as expected. Another bonus is that I've tightened the cable to the fuel pump and the tickover is now higher when cold. This stops the hydraulic pump running continuously, which is nice.

Was a bit concerned that the heater wasn't getting warm so went for a drive to try and force any air out. My conclusion is that the heater matrix is borked. If it's anything like the 'stat housing, it's probably full of silt. With the blower off, good hot air comes out of the vents. Put the fan on (which only works on the highest speed at the moment) and the air rapidly turns cold. I suspect it just can't give out enough heat to cope with the higher airflow.

Not the end of the world, as I do have a replacement dashboard to go in at some point, but a little frustrating. Also, the rad fan switch is the wrong one. Anyone got one with three terminals NOT in a line?

Brian · Post by **Brian** » Sun Feb 05, 2012 6:19 pm

Dollywobbler wrote:
New stat isn't quite right I don't think. It can move about beneath the circlip. It's the right size, but doesn't seem to have a thick edge like the one that came out. Thought I might as well fit it anyway and see if it works.

Should be a rubber gasket that fits over the thin outer edge of the stat.
Normally just disintegrates on removal.
Does not normally come with the new stat though.

I have a spare used working 3 pin rad switch, "A "pin configuration, you are welcome to have, Just PM me your address and I will pop in the post.
Should get you out of trouble for a while.

I have successfully used silicone sealant for thermostat and water pump gaskets. Just make sure the mating surfaces are clean and true,

Valve grinding past on a glass sheet works wonders.

Good Luck

Post by **mat_fenwick** » Sun Feb 05, 2012 7:18 pm

It might be worth disconnecting the hoses to the heater matrix and flushing out with a hosepipe/pressure washer. I've had good results doing that in the past.

Dollywobbler · Post by **Dollywobbler** » Mon Feb 06, 2012 9:48 am

Thanks Brian. I'll drop you a PM.

I did wonder if the thing on the edge of the old 'stat used to be a rubber thing - now I know it was! I smeared a bit of silicon sealant around the stat to seal it into the housing and it seems to be working fine.

The housing gasket actually survived surprisingly well, so the smear of sealant wasn't as necessary as it might have been.

Mat - I refuse to do any more work on the cooling system for now. Anti-freeze is not cheap! However, at a later date, I'll bung in some cooling system cleaner and/or give things a blast with a hose.

Post by **mat_fenwick** » Mon Feb 06, 2012 10:27 am

Fair enough. Given that it's fresh and (should be!) nice n' clean, I'd try and collect it for re-use when you do give it a go, so the only coolant lost will be that which remains in the heater matrix.

Brian · Post by **Brian** » Mon Feb 06, 2012 1:18 pm

Dollywobbler wrote:
Thanks Brian. I'll drop you a PM.

Posted am

PM sent