Random overheating
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Trailering
Joined: Mar 2024
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Random overheating
Hey guys I got a 98 f150 lariat with the 4.6 it has about 280k it has a new Three core radiator water pump OEM thermostat hoses it's even had a full system flush of Blue devil cleaner but I still run into the problem and it doesn't matter the speed it could be 30 it could be 70 and it'll just start getting hot it'll get about 3/4 on the gauge it won't touch the red but gets a little hotter than I like it but comes right back down 10-15 minutes later it'll do the same thing and it does it randomly yes I have burped the system done did that twice there is no air pockets there's no head gasket failure I have a kit to test that in the passed only thing I haven't done was replaced a radiator cap after I run it and it's still very hot I'll undo the cap and it makes a hissing noise and kind of pops I believe that's normal is there anything that I'm missing it doesn't use any coolant and it has good brand new coolant in it as well little confused I don't want to hurt my engine
Fleet Mechanic
Joined: Jun 2023
Posts: 1,352
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From: WA
Hey guys I got a 98 f150 lariat with the 4.6 it has about 280k
it doesn't matter the speed it could be 30 it could be 70 and it'll just start getting hot it'll get about 3/4 on the gauge it won't touch the red but gets a little hotter than I like it but comes right back down 10-15 minutes later it'll do the same thing and it does it randomly
it doesn't matter the speed it could be 30 it could be 70 and it'll just start getting hot it'll get about 3/4 on the gauge it won't touch the red but gets a little hotter than I like it but comes right back down 10-15 minutes later it'll do the same thing and it does it randomly
There are basically two cooling conditions - one uses the fan to push air through the radiator, the other uses vehicle speed. It helps to separate those two.
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Trailering
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It'll just rise up to like 3/4 thought or a little more. But It will only sit there for a few seconds and slowly easy way back down few minutes later it'll go back up a couple seconds it goes back down now on top of that I lose all heat the moment it starts
Fleet Mechanic
Joined: Jun 2023
Posts: 1,352
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From: WA
Does OEM mean Motorcraft or MotoRad? Did you mean OE or OEM? Not the same thing.
Not an expert but that looks like the air pocket or bad thermostat problem.
https://www.rockauto.com/en/catalog/...hermostat,2200
Not an expert but that looks like the air pocket or bad thermostat problem.
https://www.rockauto.com/en/catalog/...hermostat,2200
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Trailering
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Fleet Mechanic
Joined: Jun 2023
Posts: 1,352
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From: WA
Again, not an expert, haven't even changed the thermostat on mine yet, but I've read quite a bit across the internet about the thermostats. Usually it's with the newer models though.
But, here's a 97 story -
https://www.expeditionforum.com/thre...problem.56413/
"16. All that I can tell him and you is that in my case, two NAPA thermostats that test good in boiling test could not handle hot weather in my 5.4l, and when replaced with Motorcraft works perfectly. That's not a guess, that's a fact."
You should be able to get Motorcraft at Oreilly's.
https://www.oreillyauto.com/detail/c...at/mot0/rt1254
But, here's a 97 story -
https://www.expeditionforum.com/thre...problem.56413/
"16. All that I can tell him and you is that in my case, two NAPA thermostats that test good in boiling test could not handle hot weather in my 5.4l, and when replaced with Motorcraft works perfectly. That's not a guess, that's a fact."
You should be able to get Motorcraft at Oreilly's.
https://www.oreillyauto.com/detail/c...at/mot0/rt1254
Last edited by BareBonesXL; Jan 30, 2025 at 12:34 PM. Reason: Errors
More Turbo
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Trailering
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Brand new thermostat I did two of them just to make sure I didn't get a faulty one and I drive an hour one way each day to work if it was that bad I'm sure it wouldn't get a couple minutes down the road before I complete overheat and as I said this is on and off randomly throughout the drive. This is very confusing because everything is flowing smoothly radiator flows good and the block as well I can stck a water hose in the thermostat hole and water will flow right through the block to the lower rad hose
Fleet Mechanic
Joined: Jun 2023
Posts: 1,352
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From: WA
It's the design of the MotoRad's that seems to be a problem. They're not faulty, manufacturing-wise, they just don't work well as designed. Don't know why, it just is. For all of the work that you're doing, throwing some money at a Motorcraft thermostat might be worth the gamble.
I don't know if you read the thread I posted above but the two NAPA T-stats were MotoRads.
"3. Bought NAPA recommended thermostat (NAPA branded, but motorad 195F, ..."
I don't know if you read the thread I posted above but the two NAPA T-stats were MotoRads.
"3. Bought NAPA recommended thermostat (NAPA branded, but motorad 195F, ..."
Hotshot
Joined: Jul 2020
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From: Near Salt Lake City
Try raising the front of the vehicle to add more coolant, or take a heater hose off and fill the motor with coolant
Classic sign of low coolant is an overheating motor with a cold upper hose
Cross-Country
Joined: Aug 2024
Posts: 89
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From: Northern VA
While I agree with @manicmechanic007 , I recently replaced mine with a Murray from O'Reilly. It was all they had in stock. The one that was in it would not let the motor get above 160. It was a 192 degree Motorcraft. It may well have been stock from 2003 though. Who actually makes the Motorcraft one? U.S. company? Canadian, Mexico, China, the UK? Who knows these days. I am willing to bet it is the lowest bidder each year when the contract is up for renewal. Probably never even heard of the actual manufacturer's name that stamps Motorcraft on them for Ford to sell at an obscene profit.
Honestly in my many decades of driving, this is the only thermostat that I have had fail. I have had more vehicles than I can count. I have replaced many thermostats because when working on other things, if the housing came off or the system opened, I just replaced it as best practice. I never really thought about the brand, just what the parts store had since this goes back much further than Amazon and the internet.
Honestly in my many decades of driving, this is the only thermostat that I have had fail. I have had more vehicles than I can count. I have replaced many thermostats because when working on other things, if the housing came off or the system opened, I just replaced it as best practice. I never really thought about the brand, just what the parts store had since this goes back much further than Amazon and the internet.