Bad Coolant temp sensor?
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Bad Coolant temp sensor?
2002 E350 with a 5.4L. I have the van built out as a camper, but haven't been out in it much last few months so I usually start it an let it idle for half hour or so every week. last week I came back to turn it off after idling for 30ish min and the temp gage was pegged in the red and it was showing a CEL and a P1299.
turned it off, let it cool down and came back the next day. Next day cleared the OT code, started and let it comes up to temp normally, but once the gage gets close to normal temp, it shoots into the red and declares the code again. I replaced the thermostat just cause it was $10, but same scenario repeated with a new thermostat.
the speed at which the gage goes from a little below normal to pegged makes me think its an electrical issue. the block isnt heating up that fast.... is this a common failure mode for the sensor?
thanks,
E
turned it off, let it cool down and came back the next day. Next day cleared the OT code, started and let it comes up to temp normally, but once the gage gets close to normal temp, it shoots into the red and declares the code again. I replaced the thermostat just cause it was $10, but same scenario repeated with a new thermostat.
the speed at which the gage goes from a little below normal to pegged makes me think its an electrical issue. the block isnt heating up that fast.... is this a common failure mode for the sensor?
thanks,
E
Fleet Mechanic
Joined: Aug 2004
Posts: 1,276
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From: NE Tennessee
I think there are 2 temp sensors. One for the computer and one for the gauge (maybe I'm thinking of Chevy)? They aren't expensive so it may be less hassle to just replace them. BTW was the coolant boiling or the motor seem excessively hot? Have you checked your water level just to be sure? No good way to test them unless you can bring water to a known temperature and do an ohm test on the leads. Most sensors will fail to the bad side instead of the good. Cautious over no-info or low reading. Its why the fuel level gauge fails on E instead of F. I'd drive on F all day and never realize it wasn't reading correct. lol
Hotshot
Joined: Dec 2012
Posts: 11,267
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From: Las Cruces New Mexico
Its the cylinder head temperature sensor, its common for them to fail. In order to get to it you will need to remove the alternator and loosen it up with an open ended 3/4" wrench. Its a pain in the **** but doable. Make sure the connector is in good shape as rodents love wire insulation especially that particular wire since it resides underneath the intake manifold front driver side.
One more thing if you have an OEM intake manifold theres a chance you are going to have to remove the intake manifold as they have cover underneath them blocking the CHT.
One more thing if you have an OEM intake manifold theres a chance you are going to have to remove the intake manifold as they have cover underneath them blocking the CHT.
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Replaced the coolant temp sensor (one by the thermostat/upper radiator hose outlet).
problem seemed to go away for 2-3 starts. Third start the problem came back slightly modified. Gage pegged again, CEL did NOT come on, no code, but the oil temp idiot light came on.
Still thinking it may be the CHT sensor, but the Oil Temp light makes me think it might be some more complicated electrical issue.
any way the CHT sensor would give these symptoms?
also of note, I did check the coolant temp sensor that I replaced in boiling water on the stove. Resistance did seem to be really erratic at about boiling...
problem seemed to go away for 2-3 starts. Third start the problem came back slightly modified. Gage pegged again, CEL did NOT come on, no code, but the oil temp idiot light came on.
Still thinking it may be the CHT sensor, but the Oil Temp light makes me think it might be some more complicated electrical issue.
any way the CHT sensor would give these symptoms?
also of note, I did check the coolant temp sensor that I replaced in boiling water on the stove. Resistance did seem to be really erratic at about boiling...
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Started on the CHT yesterday. Harness looks ok (not rodent chewed). I think I do have the OEM intake. It’s pretty tight access in there. I can barely get an open end wrench on it at all. Tried a Ritchie ratchet but there’s not enough clearance on the sensor to get the box end around it.
Any tips or tricks to get it without pulling the intake or should I just bite the bullet? There’s a coolant transfer pipe that looks like it goes between the heads and also holds the thermostat/upper radiator hose. Is that thing removable? It looks like that would open up a lot of space and looks quite a bit easier than pulling the intake.
Any tips or tricks to get it without pulling the intake or should I just bite the bullet? There’s a coolant transfer pipe that looks like it goes between the heads and also holds the thermostat/upper radiator hose. Is that thing removable? It looks like that would open up a lot of space and looks quite a bit easier than pulling the intake.
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Started on the CHT yesterday. Harness looks ok (not rodent chewed). I think I do have the OEM intake. It’s pretty tight access in there. I can barely get an open end wrench on it at all. Tried a Ritchie ratchet but there’s not enough clearance on the sensor to get the box end around it.
Any tips or tricks to get it without pulling the intake or should I just bite the bullet? There’s a coolant transfer pipe that looks like it goes between the heads and also holds the thermostat/upper radiator hose. Is that thing removable? It looks like that would open up a lot of space and looks quite a bit easier than pulling the intake.
Any tips or tricks to get it without pulling the intake or should I just bite the bullet? There’s a coolant transfer pipe that looks like it goes between the heads and also holds the thermostat/upper radiator hose. Is that thing removable? It looks like that would open up a lot of space and looks quite a bit easier than pulling the intake.
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