Motorcraft thermostat from Rockauto

Digitalchaos

Registered User
Just installed this; label said YF1Z-9775-BA, Thermostat said XF1E-8575-BA. Is this the number to the n/A 3.8? Did they run out and put this label on the box they sent? I found this out after filling up and watching coolant poor out the bottom.

Any help clarifying these numbers is appreciated.
 
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The coolant pored out from where? Our t-stats need to be turned clockwise to a lock position before you put the gasket on. Did you open the bleeder screw before filling it with coolant?
 
A steadily increasing stream of coolant was being emitted from the bottom of the thermostat housing. Bolts should not have been too tight, housing was checked for warpage against a straight edge and found to have none. The thermostat was turned in a clockwise position and locked into the housing. There was a little copper-colored peg in the surrounding edge of the unit, is this the weephole perhaps? The cooling system's vent cap was open, and the car had not been run.

I was originally questioning the gasket in another thread because it had an odd fit, but others seem to think it was correct. All the material lined up with the holes & edges, simply a tab of gasket material was protruding from the top of the housing. This is also a new Motorcraft gasket from the same source as the thermostat.

I noticed a very small (1/8"?) 3 sided indentation at the bottom edge of the intake, where the housing meets. It looks as if it was designed to be there.

The previous aftermarket non-locking thermostat did not leak significantly, though it lost slight coolant over time. It was replaced for this reason and for its lack of a weephole.

I have thus far been unable to find the part number for this Motorcraft thermostat, XF1E-8575-BA, listed anywhere. I wonder what car it was designed for?

Thanks..
 
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You should ask a guy called "fast Ed N" because he works for Ford and can tell you anything about their part numbers. Good luck
 
I think I got a stant unit from pep boys. Works great. Now, the gasket I got with my rebuild kit, which was a felpro, had coolant leak right through the sides. I had to use rtv, and a lot of patience to get it to seal correctly.
 
that's alright, i couldn't find a t-stat gasket anywhere in the southern california area to fit it. i had to make one =\
 
Are these thermostats more prone to leakage compared to other cars? Is there a design difference which makes them this way? I just changed motor mounts, plugs/wires, power steering fluid, other misc items, and this is proving the most difficult! :D

Thanks. Hopefully I will find the correct number at ford.
 
I just had this problem. I got the thermostat from Rock auto and it would not fit right in the housing no matter how I tried it. I tried turning clockwise but the thermostat I had would not mate up right and the gasket surfaces would not go together tight. I went to napa and bought another thermostat then went to carquest and compared theirs to napa and they were identical. So I threw the Napa one in. (195DEg) The only thing is there is no "locking" into place with the store thermostats they just fit in the indented part on the housing. You can turn the thermostat and it's a nice smooth turn. (No latching on or locking). I used plenty of RTV on both sides of the gasket but have not tested yet.
 
Oh and I think Rockauto is mailing out the wrong ones because there is no way that thermostat fits without forcing it and that is why so many people have leak problems?
 
An update: The second part number I mentioned at the top of the thread, XF1E-8575-BA, has superceded the original number, YF1Z-9775-BA. This makes this a new version of the correct thermostat.

Now I wonder if Ford redesigned the unit differently causing it to no longer fit in the SC housing. Is the housing different on a N/A 3.8? The thermostat is the same, the gasket is different.

As to my problem, I took the gasket, Motorcraft thermostat, tons of Copper RTV, and dabbed the gasket into place without locking it. It held. Then I RTV'd both the housing and intake surfaces, put the Motorcraft gasket in between, and bolted it up. I really hope it doesn't leak this time, my time to fix it has run out.

So far the information that I have seen here indicates that majority of thermostat leaks are due to a bent housing. Mine appears to be vertically unstable from some previous person overtightening.. that is I can rock it top to bottom just slightly when its sitting against the intake. If this is true, then the only solution short of possibly RTV is to replace the easily damaged 180 dollar part. :eek:
 
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