Replacing thermostat

davejake

3 is company too!
81 FI 1500 X1/9. I want to replace thermostat.

Can I remove the 3 bolts without taking off the whole housing it’s bolted too? Those 3 bolts look like a challenge to get to!

Advice?
 
It may sound like a PITA, but removing the whole assembly is actually easier... especially since the three small M6 bolts hat hold the cover on get pretty tight and have a tendency to snap off ... it would be a good idea to remove the assembly and hold it in a vice after soaking the bolts with a penetrating lubricant.

SteveC
 
I agree with Steve on that. Those three bolts are very difficult to get to nervemind ensuring the lower half is seated and sealed properly. Taking off the whole assembly allows for a good cleaning and thorough install of the thermostat. I personally used the stant superstat. Seems to work very well. Sells for cheap too on rockauto.
Not a bad idea to replace gaskets at that time as well.
 
Definitely soak the attachment bolts first, I broke off one of the head-attachment bolts when I first got my car; it hadn't made it all the way home (6 mi.) before it overheated; it got extra form-a-gasket to get home...
 
Just for reference...
 

Attachments

  • B8B45E16-D249-4695-9673-CF2EAA50EADA.jpeg
    B8B45E16-D249-4695-9673-CF2EAA50EADA.jpeg
    144.4 KB · Views: 116
+1 to the consensus about it being easier to remove the entire housing vs the stat cover/elbow. Total PITA to get to that one 10mm capscrew squished between the stat cover and the block.

To do a good job you will need the two flat gaskets (head<->stat housing; stat housing<->stat cover/elbow); the square profile o-ring that seats the stat flange into the stat housing***, some gasket sealer for cooling system applications (the gray Permatex seems to work well); and some anti-seize for the three stat housing<-> cyl head capscrews (2 long 1 short).

***Typical replacement stats like the aforementioned Stant are ever so slightly smaller in flange OD as compared to the OEM unit, so they will seem to "swim" in the o-ring, but most people don't seem to notice or mind.
 
Also, make sure you get the correct housing to head gasket, there are several iterations and if you use the wrong one you will get coolant where you don't want it.
 
Typical replacement stats like the aforementioned Stant are ever so slightly smaller in flange OD as compared to the OEM unit, so they will seem to "swim" in the o-ring, but most people don't seem to notice or mind.
This issue with the non-original T-stat diameter being smaller can be a real pain if you try to reuse the old O-ring on it. They get a bit stretched out with age and are even larger diameter than a new one, and they get firm making things worse. It can even cause it to not seal correctly. I agree with Dan, get a new O-ring along with new gaskets. A new O-ring will still fit loosely on a non-original T-stat (i.e. any of the Stants or similar commonly available replacements), but it will be better than the old one and should go back together without leaking. That being said, if you are OCD like me it may still bother you how these T-stats fit. The correct diameter replacement is available, but is isn't nearly as inexpensive as the others. The non-original T-stat is the same as early VW's, and can be found extremely cheap in any temp desired from any parts source. Also, some time ago I bought a new O-ring from RockAuto, listed for the X1/9, but it was not correct. Therefore it might be best to get the O-ring from a source that knows the difference.
 
On the subject of replacement T-stats. Does anyone know of a "high flow" design T-stat that can be used? I'm referring to the ones that look something like this:
91015703_L_4009a434-84b3-4052-b51c-c85e9319649d.jpg
But of course it will need to be the two-stage type and correct size for the Fiat system. At one time they were only for American V8 applications, but I'm seeing a lot more available these days...including for imports that have the two-stage (bypass) systems. These have larger overall passages to allow greater flow when open. Not sure if it will make any difference with our small water pumps but I would like to experiment with the concept.
 
Absolutely remove entire housing from block.

I heated entire housing in a vat of old oil (not too hot-fire) for an hour, removing periodically to see if m6 bolts were loosening up. Housings are getting harder to find as the m6 bolts love to snap off.

I used copper anti seize upon reassembly for every fastener.
 
Generally speaking for any/all engines I prefer to replace ALL coolant system related hardware (bolts, washers, loc-washers, studs, etc) with stainless steel. In addition to the use of anti-seize.
 
Generally speaking for any/all engines I prefer to replace ALL coolant system related hardware (bolts, washers, loc-washers, studs, etc) with stainless steel. In addition to the use of anti-seize.
Does this cause any "dissimilar metal" issues?
 
I swapped out the factory bolts with flanged head bolts. Lots of copper paste

X19-1195.jpg


What's nuts is that the ring seat is flush, every other manufacturer that uses these (like Volvo) doesn't make the seat flush, the seal sits proud so that it will seal against the mating surface. That way, no gasket is required.

X19-1193.jpg


X19-1194.jpg


X19-1196.jpg


I switched back to the Savorin (available from MWB, at much greater cost than SuperStant) when I was trying to eliminate every possible cause of my overheating at idle condition some years back.

X19-CIS0004.jpg
 
What's nuts is that the ring seat is flush
It is an odd arrangement. Especially since it uses a good "grommet" rubber seal around the T-stat, but still requires a old fashion paper gasket as you say.

"Savorin" is the 'original style' I was referring to earlier; the rubber O-ring/grommet fits them correctly and the assembly fits the housing correctly.
 
That would be "Savara" branded... thermostats, heater taps and other small parts, OEM parts.

The square section O ring is actually "split" on the inside edge, so it fits around the thermostat's edge and seals.

SteveC
 
Back
Top