to cool
Posting Guru
Joined: Nov 2001
Posts: 1,743
Likes: 2
From: Ft Scott
Are you sure you're using the right one? 94-95 use a short stem thermostat and 96 and later use a long stem. If you put a short t'stat in a long stem pump the bypass will never close and the water won't circulate completely through the block and will cause major temp variations in different parts of the block. It's possible to overheat the rear of the heads and still have the gauge sitting on "C"
Are you using a real temp gauge or the factory gauge? What are your temps?
Even with a 203* t'stat in 115* temperature pulling a trailer up a mt pass in Az mine would run 205* on an aftermarket gauge and straight up on the factory gauge, these things normally run pretty cool.
Are you using a real temp gauge or the factory gauge? What are your temps?
Even with a 203* t'stat in 115* temperature pulling a trailer up a mt pass in Az mine would run 205* on an aftermarket gauge and straight up on the factory gauge, these things normally run pretty cool.
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Freshman User
Joined: Mar 2008
Posts: 42
Likes: 0
From: lowell oregon
more thermostate info
about every five or six hundred miles, themostat goes bad. when i put a new one in, the guage come up to the 'o' and normal, runs great, then, the guage starts bouncing up and down between the n and the c and fan won't turn on. on my 4th one now in less than 4k miles. help, help, help.
last thermostat was factory ford long stem.
last thermostat was factory ford long stem.
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Freshman User
Joined: Mar 2008
Posts: 42
Likes: 0
From: lowell oregon
i think the tstat goes bad beacuse when i replace it the temp gauge works as normal comes up to the o and stays there then after a few hundred miles it goes up an down fast between the c and the n the fan is clutch style and you can hear it come on when the gauge gets to the r ancools down the o and quites down so you know it is working this dosnt happen when the gauge is going up an down thanks
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Postmaster
Joined: Nov 2005
Posts: 3,168
Likes: 10
From: San Ramon Ca.
Whatever the issue is it's not the thermostat. You may just have air in the system that needs to purge. Also the fan clutch may be going south. Radiator may also be clogged up. But my bet is on air in the system. Check the fan for play while the truck isn't running. Water pump bearing check. You may have to pull the thermostat again and make sure you have coolant up to where the thermostat goes before you install it. Then install the thermostat and housing. Pull the upper hose off the radiator and keep adding fluid until it runs out of the radiator. Button it up. That should eliminate most of the air. The system should then purge itself during normal driving. Turn the heater control to full heat for awhile also so you get coolant flow through the heater core. Keep an eye on the reservoir for a while until it settles down. Thats about all I can think of at the moment.
Last edited by pjwoolw; May 29, 2009 at 09:05 PM. Reason: addition
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VT Chapter Ldr
Joined: Apr 2004
Posts: 96,140
Likes: 294
From: Orange, Vermont
If your thermostat is sticking that quickly after you put a new one in, my guess is your anti freeze is dirty, maybe rusty or too thick or gummy. Have you checked your anti freeze to see if it is good?
Postmaster
Joined: Nov 2005
Posts: 3,168
Likes: 10
From: San Ramon Ca.
Certainly could have allot of junk in it. But I would think it would stick open with debris. That was the case on my 97. Big hunk of RTV stuck in it.
Steve, if you do have to replace it again get a Motorcraft from the dealer or wherever. I've never had any luck with other thermostats on these rigs.
Steve, if you do have to replace it again get a Motorcraft from the dealer or wherever. I've never had any luck with other thermostats on these rigs.
VT Chapter Ldr
Joined: Apr 2004
Posts: 96,140
Likes: 294
From: Orange, Vermont
I bought my 96 last july and my temp gauge would not even get up the line before the n, so I got a 203* from diesel site and now it stays in the middle of normal. Nice to have heat in the winter. As far as I know, diesel site is the only place you can get a long stem 203* thermostat.
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Freshman User
Joined: Mar 2008
Posts: 42
Likes: 0
From: lowell oregon
ok took all the info you guys gave me and this is what i did . took off the top radiator hose , started it up , let it warm up until the t stat opened hooked hose back up , 1000 miles later an no problems guess i wasted all the t stats i changed, i did learn my lesson COME HEAR FIRST WITH MY PROBLEMS thanks especially to pjwoolw