I would like to install a new "Stant" SuperStat thermostat in my 98' F150 5.4L as the 3 yr. old fail-safe thermostat I installed is now starting to stick open and run at 180 instead of 195 degs. Looking up the options on "Rock-Auto", I found that the Stant SuperStat is 192 degs opposed to the OE 195 degs. Says it's OE but has better metering and flow/better engineered.

Would this affect the way the PCM runs the engine, negatively perhaps? Too rich, etc. I know it's a small difference but these things are designed where one thing affects another computer wise. Your thoughts, positive and negative please.

Thanks.

 

I put one in from Advanced Auto called Moto Rad.
It's dead on.
The hysteresis temp variation is between 196 and 202 with 198 to 200 being the norm depending on outside temp and the load.
Watched it the first time coming up to temp it had me concerned by going to 206 before it opened the first time then settled down since that first time.
There was a detectable shift in operation between 185 and 198 but still work very good..

 

I recommend you get the Motorcraft, myself and many others have had nothing but problems with aftermarket thermostats, I have used bot Stant and Motorad with terrible results. In my situation, the Stant lacked the bleed valve, which not only made it much harder to properly bleed it, but after only a short while, maybe a week after it was installed, it began to open prematurely.

The genuine Motorcraft brand is only marginally more expensive, but it tends to outlast 3 or 4 aftermarket ones, and all the ones I have every used worked perfectly, and I have never had to replace one a second time.

There are some things I will use aftermarket parts for and there are some things where OE is just plain the best there is at any price. Thermostats, ignition parts, and fuel pumps are all things I would use only OEM replacements for.

 

Thanks for that info gents. I've had 2 after-markets fail and will try the OE Motorcraft.

So your saying the Motorcraft does have the bleed valve?

 

When it's near 100 outside, my coolant temp climbs to 210-212. Is this normal, or should I replace my thermostat?

 

If it works better in cooler weather, then no, the thermostat is opening, and flow is not the problem. Heat rejection is the issue. Makes sure you clean the dirt, bugs, and leaves off the front of the radiator/condensor and that the fins are not bent over, this maximizes flow and efficiency. If you fan isn't working properly, you could have issues. Make sure you have fresh antifreeze in there with NO TAP WATER in it. Tap water causes corrosion, and corrosion plugs the passages in the radiator, and that can cause heat build up. 210-212 is not really a problem though, you are still within the normal safe temperature. Not saying not to check out and maintain your system, but the temps you are seeing might be normal.

 

210 is normal, actually pretty good for 100°F, mine runs that temp when we are in the 90's.

 

So your saying the Motorcraft does have the bleed valve?

 

I agree, I've also had problems with aftermarkets having their no-fail feature lock open prematurely and seen others with no bleed hole.


On a side note, the Ford oem stat on a 4.9l is shaped to twist lock into the housing so it doesn't fall out when mounting the housing vertically. I've never had an aftermarket do that so far.

 

Depends on the application. In my vehicle it does, on your specific year/model it might not.

 

I ordered one and will have to check it out. I wonder if I could drill a small hole if it's not there? I'll talk to Motorcraft to.

 

I just received the Motorcraft RT1196 from Rock auto. It has the air bleed hole/valve. it looks very well constructed, HQ!

 

I noticed the Motorcraft RT-1196 thermostat I ordered has a 192 deg. rating stamped on it? isn't the OE 195 degs.?

I didn't get a chance to install it last fall. It's been at 194 degs. all winter. It always used to level off once warm to 198 degs. until it acted up last summer and started jumping around all over the place.

Has it been superseded since 98' or is the OE temp supposed to be 195 degs.?

P.S. I monitor the temp from my Edge Evolution.

 

Close enough.
They are not that precision!
Good luck.