So I finally got round to changing the thermostat on my 150 mJTD (16V) Croma. I'd been putting it off due to the apparent difficulty of changing it. It actually wasn't that bad. I didn't even fully drain the system as the coolant is only 18 months old. I used a hand syringe type pump to first empty the header tank. I then connected it to the bleed point on the metal pipe that runs across the front of the engine and sucked out as much as possible from there.
The other key was access. I removed the battery and the battery tray completely. I also disconnected intake hose between the intercooler and stop valve (on engine) at the stop valve (2 M7 RIBE bolts). Moving these out of the way gave good access. I then removed the nut holing two metal pipe brackets to the thermostat housing. I removed the clip on the short hose connecting the pipe across the front of the engine to the black pipe on the thermostat hosing stud (I had to cut this clip). The pipe was pulled off and moved down out of the way. The other pipe on the stud has a slotted bracket and enough movement to pull off without disconnection The temperature sensor plug is removed by sliding the yellow locking piece up and lifting the tab below it. I unscrewed the sensor to get better access to the clip on the pipe behind it. The 3 small pipe clips were released in-situ. I then undid the two bolts holding the housing to the block. I had a tray positioned to catch the small amount of coolant that escaped. I could then cut the clip on the large hose. New thermostat seal was pressed into place in the housing, Large pipe (with new SS worm drive clip) pushed onto stub pipe (but not tightened) and housing bolted to block. 3 small pipes pushed on and original clips reused. Then large pipe snugged up and clip tightened. Note in photo that the locating pip on the spigot does not line up with the notch on the hose. The pip is in a different postion to the original. The housing is a Gates TH36988G1 and seems good quality. First metal pipe put onto stud and then second one fitted along with reconnecting at front of engine. Coolant topped up with fresh mixture. I need about 1.5 l total. Note that coolant is toxic to dogs and especially cats and the sweet odour attracts them so don't leave any open drip trays or puddles about. I bleed the system and all was fine. Temperature indicator goes to mid (vertical) position and sticks there. I could check by feeling the large hose from the thermostat that it was not opening until the engine was up to temperature.
Oil and filter change tomorrow.



Robert G8RPI.

I've got a post somewhere about when I replaced my Croma's stat.

Had to do it twice due to the OEM/Aftermarket housing did not have the "clinch" pips to hold/retain the square "o" ring which dislodge on fitting. Second time around a couple of drops of Super Glue sorted the problem.

Even with the battery removed (and pipes) it is a little tight and fiddly if there is no o ring retention.

The Gates housing has the seal (it's square section so technically not an "O" ring, Sorry I'm a pedantic engineer) holding pip's so no worries there.

Robert G8RPI.

Yes mine was a Gates replacement. And yes it is a square as opposed to "O" ring.

If you look at the Fiat original housing there are little clinch points to securely hold the square ring in place during fitting. My Gates unit did not have these and the square ring slipped during the fiddly relocation of the housing body. Probably just my bad luck (or you were lucky).