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Stump Jumper · 05-10-2016, 08:01 PM

Hello,

My Uncle has a 2001 Class A motorhome with a Ford V10. On a recent trip, he started having problems with the motor going into limp mode. When the temp gauge would get near the normal operating range, it will suddenly spike and the computer will go into limp mode. After cooling down, it will run fine until it gets near normal temp and then do the same thing all over again.
I have read about the problems with the cylinder head temp sensor and the crossover tube fix. (TSB 06-21-15. However, I thought that this usually affected later models.
He replaced the cylinder head temp sensor and the problem is still occurring. He has a scheduled trip coming up in 2 weeks. Any ideas?

mrt_1111 · 05-11-2016, 01:07 AM

Have you tried using a OBD scanner to pull any codes? If you dont have a scanner some places like autozone will do it for free.

Check for coolant.

How do you know the overheat is false? Is the fan clutch working. Put a thermometer is the recovery tank. The guage in the dash is for entertainment purposes, it will only give a general idea of the temperature.

Check for a stuck thermostat.

Could be a collapsing coolant hose.

Stump Jumper · 05-11-2016, 07:12 AM

He has already replaced the thermostat and put a new Ford cylinder head temp sensor in it. Scanned it last night and the scanner is still saying it is the cylinder head temp sensor. Could be a bad sensor from Ford, but with all of the posts that I have read about the later year V10's with the same problem, it has me wondering...

GBRG07 · 05-11-2016, 07:32 AM

Sounds more like a coolant temp sensor. It is beside thermostat.
Would be nice to monitor it while going through the warmup.
Could be an open at certain temp. Have seen lots of trans temp sensors do that.

Codes would be a good place to start for sure but if the sensor is cheap?

Stump Jumper · 05-11-2016, 08:35 AM

Might replace the coolant temp sensor as well, but the code reader pointed to the cylinder head temp sensor...

TeJay · 05-11-2016, 09:03 AM

Diagnose, diagnose, diagnose. Determine if you really do have an overheat issue or just a false reading going into the computer.

Try an infrared temperature gauge and shoot it all down and around the hot stuff to get an idea of the exact temps. Thermostat housing before and after the thermostat. Check hoses, everything to get an idea.

You should be able to duplicate the happening setting in the drive.

Some have told me that those temp gauges are not very accurate. Verify if and how much the temps are off. Boil some water. Insert several thermometers and establish your water temp. Now shoot it with the infrared gauge and if it's off 5#'s so what. Just adjust your readings by 5#'s

TeJay

winnie32v · 05-12-2016, 04:52 AM

I use an OBD reader (eBay) and read the actual temp from my smartphone using the Torque App. This might let you know what the computer is "reading" and using to regulate the many engine functions.
The IR "gun" is a good idea for actual on-the-spot temp readings.

Keep us advised.....Thanks.