Today i decided to flush the coolant and change the thermostat while i was in there. It was a first for me but seemed to be going well until i cracked the thermo housing when replacing it.

Any tips on replacing the new one tomorrow - sanding where the housing sits on the engine? should i apply anything to the new gasket before cranking it down? etc.

Also the new thermostat didn't really twist and lock into place like i read it should.

Anything related would be appreciated.

Thanks.

 

I have never seen any 300 where the thermostate 'twisted and locked' into place. the engine takes the standard 54mm thermostate like 90% of other vehicles - totally flat surface that fits inside a slightly routed out area. getting them to stay in place when replacing is fun - I tend to glue them in place with a little rtv.

just scrape the block surface good and flat

 

Hey, Thanks..

Quoting Haynes Manual - "13 Turn the thermostat clockwise to lock it in position on the flats cast into the elbow."

Also, whats rtv?

 

Make sure all surfaces are clean. You should see a small rib around the thermostat that kinda helps it stay centered when instaled in the hole. Run your finger around the recessed rim of the hole in the engine. You should feel a small dimple on each side that will catch on the thermostate rim. (when turned a quarter turn) in the hole. This holds the thermostat in place while you install the gasket and housing and get the bolts started. The thermostat should have a small vent hole to purge air from the system. This vent hole should be at the top.

RTV stands for Room temperature vulcanizing. Commonly known as Form-A-Gasket. It is a sealant that comes in a tube. You apply a thin coating to the gasket. To help seal against leaks. RTV means it will cure at room temperature.

Two reasons for cracking the housing. One the thermostat slips down a bit and gets pinched cracking the housing. But more so just tightening the bolts to tight. The housing is made of soft stuff and will crack easily if over tightened.

 

I also just cracked my housing and had to get a new one. If you put the thermostat in the new housing then put the gasket on over it w/ gasket gunk, it stays in place.

My freaking problem now is the holes on the thermostat housing don't line up perfectly with the ones on the head.

If I get one bolt in, I can't get the other in, without it going in at an angle...which doesn't work.

Did I get a defective housing, or should I just drill the holes out a little bigger to get the bolt in straight?

 

Thanks for the tips shotgun..

saint_berzerker - I also had the exact same issue when installing mine. what worked for me was to install the bottom bolt first, just barely, then work on the top one.. these replacement housings are made from junk metal and once i got the top slightly threaded by hand, i worked it in slowly with a ratchet and it came together with a little bit of force. I was close to drilling mine out as well.

After replacing the housing, thermostat and the coolant temp sensor(which i broke removing the first housing), the engine seemed to run better, smoother at idle when warm, and the temp gauge isnt fluctuating somewhat erratically anymore. Also have seem to lost the sputter or misfire at low rpms that i noticed in 3rd and 4th.

Pretty satisfied, as a carpenter i'm slowly gaining confidence under the hood.

 

Thanks 123FORD. I'm just so scared of stripping the head holes out, or breaking the bolt head off when the resistance got too much.

I'm going to try a couple more times. It just seems to be off a mm or so...but ugh it sucks.

 

you could use a rounded file to move the hole ever so slightly on the housing-or a drill just take your time-could just be the casting slag -a small area of left metal over where they made it they probably don't clean or detail them too good!

 

I recently had to replace ( 92 F-150 ) mine. I was replacing a sticking thermostat and when putting it back together I guess I cracked it because it leaked.
I had the same problem with the new one, the mounting holes in the housing were drilled too far apart. I ovaled them a little with a dremel.
I was careful putting the new one on and noticed it was not pulling up even. The new casting was too wide on the outside of the lower bolt. It was hitting the AC bracket. Back to the dremel. I took off about 1/16" or slightly more and it fit like it should.
The housing is aluminum so a dremel with a burr was an easy fix.

 

Alright heres what you do learn this trick fromsearching the archives so it isn't mine(but do use it) Glue the theromstat to the housing using super glue just a few drops around the housing. then let it dry about 3 to 5 minutes. i put mine in a vise to aid in holding.

Pick up some 1.25" 5/16-18 studs thread them in using loctite. Then when its time to put on housing just line up the holes press on, install lock washers and the nuts Toque to 18ft/lbs. This way you don't have to fumble around with trying to line up the holes.

No leaks!!!

 

A couple days after the install of new housing, thermostat and coolant temp sensor, the temp gauge in the instrument cluster shows well below normal. The heater and the upper radiator hose both warm up quickly. Maybe i am being too ****.

 

Once upon a time, I got a bad thermostat right out of the box.
Since then, I put the new one in a pan of water with a cooking thermometer and heat it on the stove. Watch careful and you can see when it opens and check the temp. Never found another bad one, but I still keep doing it just in case.
Frank

 

Room temperature vulcanizing

 

The answer to that was given in post #4 on Feb 6, 2009.

Sometimes the forum leads you to a related thread and you miss the fact that it is an old dead thread.