High Temp Problem

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Apr 4, 2020 | 10:01 AM

ScotF150

Thread Starter

Mountain Pass

Joined: Aug 2007

Posts: 245

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From: Atlanta,Ga

High Temp Problem

2004 Excursion, 6.8L w/215k miles running OE cooling system. Driving down the interstate yesterday @ 75 mph and gauges indicated an over temp condition. Engine went into limp mode, AC compressor went off, CEL came on and dash temp gauge pegged out hot. I pulled over, shut down and checked the engine compartment. Belt and hoses were good, coolant level was good and not boiling over. Everything appeared normal so I started it back up and headed out. I kept the speed under 70 and the coolant gauge was normal but as soon as I run it up above 70 the gauge started bouncing around and then pegged hot. I slowed back to under 70 and gauge returned to normal. I cruised on back home for almost 2 hours @ 70 mph without any issues. I suspect the temp sensor is the problem and will change it first. I have about 60k on the coolant and thermostat and will change both while I’m at it. Any suggestions on other issues that would cause this? Thank you for any input.

Scott

Apr 5, 2020 | 05:36 AM

JWA

Fleet Owner

Joined: Aug 2010

Posts: 21,253

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From: Reynoldsburg, Ohio

I had a similar issue with a 5.4 in an E250---turned out to be the radiator, about 264K miles at the time. I too went through the entire system, did find a leaking under pressure degas bottle however that was easily spotted from the tiny geyser.

There were no leaks, no water/oil mixing and the transmission fluid also coolant free. I did a half-assed flow test with upper and lower radiator hoses disconnected running water from a garden hose---there seemed to be no restriction. I did replace the fan clutch and serpentine belt for grins but kept original water pump. Since that swap all has been good even on the hottest days with A/C running full time, speeds typically 70 MPH and I do not tow anything.

I hope this is only a sensor but would be good to check the radiator too

Apr 5, 2020 | 02:58 PM

krewat

FTE Leadership Emeritus

Joined: Jul 2002

Posts: 42,561

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From: Long Island USA

There have been reports over the years where the PCM thinks the engine is overtemp and goes into limp mode. This might count at around 5 or 6 times I heard of this over the years I've been in the V10 forum. It could be the CHT (cylinder head temperature) sensor, but it could also be the PCM itself not reading it correctly requiring a PCM replacement.

Get a Bluetooth OBD-II dongle, Torque app on Android, and read the actual temps the computer is "seeing".

Apr 7, 2020 | 07:39 AM

ScotF150

Thread Starter

Mountain Pass

Joined: Aug 2007

Posts: 245

Likes: 3

From: Atlanta,Ga

Thanks for the replies! I’ve ordered the temp sensor and it should be here in a couple of days. I’ll get it replaced and see what happens. We want to keep the Ex a few more years so I’m going to rework the cooling system. After 16 years and 215k miles I think its time.

Scott

May 11, 2020 | 03:55 PM

ScotF150

Thread Starter

Mountain Pass

Joined: Aug 2007

Posts: 245

Likes: 3

From: Atlanta,Ga

I replaced the radiator, t-stat, water pump, degas bottle, cap, fan & fan clutch, temp sensor, belt and hoses. The temp sensor fell apart as I was removing it and the fan clutch appeared to be weak but everything else was OK. Took a long drive on the interstate (after a few trips around town) and everything is working ok for now. I'll update in a few weeks.
Scott

Last edited by ScotF150; May 13, 2020 at 08:28 PM. Reason: added t-stat

May 11, 2020 | 05:41 PM

krewat

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Joined: Jul 2002

Posts: 42,561

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From: Long Island USA

Thanks for reporting back, Scott

May 13, 2020 | 05:25 AM

JWA

Fleet Owner

Joined: Aug 2010

Posts: 21,253

Likes: 1,656

From: Reynoldsburg, Ohio

Good news indeed---glad its sorted out now.

I myself think you did the right thing replacing what you did--at that mileage hard to know what might have been next to fail. I did much the same on my own E250 at about 263K miles, been trouble free for about 30K miles and a few years now.

Indeed thanks for the update!