Coolant temp pegging out ???

RLSmith · 08-07-2012, 04:18 PM

I have a 2008 6.4 4x4 and while running down the interstate between 80-85 mph the coolant temp gauge pegs out and then it says reduce engine power. Slow down to 70 and it's fine. So I figured I wouldn't run that speed anymore but the other day pulling my airboat down the interstate it did it again and I was only going 70. The boat is light weight but it does hav some wind drag. Need to get tuis fixed before my next trip with my cattle trailer from Florida to west Virginia. I know it won't handle pulling thru the mountains. Looking for any advice.

Thanks
Ryan

**Eazydeezy** · 08-08-2012, 02:10 AM

Is the truck stock or tuned? Have you noticed any coolant under (puking) under the hood. The first place I would check is your degas botttle cap. If the system is not holding pressure, it will cause the coolant to boil before the fans turn on.

RLSmith · 08-08-2012, 06:11 PM

Yes the truck is tuned with a sct livewire. No custom tunes just canned tunes. It stays on max setting. I also have a aftermarket intake and I have deleted the burner. Just a straight pipe exhaust. I'm not losing any coolant anywhere and both egr coolers were replaced about 16,000 miles ago along with head gaskets all under warranty an while truck was still stock. As soon as the needle pegs out and it says reduce power you let off the pedal for about 15 seconds an it will drop right back to regular temp. I had my live wire plugged in to watch the temp and the hottest I seen was 200. It runs around 194 to 196

**Eazydeezy** · 08-08-2012, 09:31 PM

Try changing the degas bottle cap. It's a $5 part at any parts store. My truck was doing something similar and the cap fixed it.

**neeltburn** · 08-09-2012, 03:18 AM

I am not sure if the 6.4L has a similar Degas bottle but I know that some 6.0L Degas bottle cracked. You can rent a pressure tester from autozone I believe that have one that has the correct adapters. The other option is to do a hydro-carbo test on the coolant, it tells you if there are exhaust gasses in the coolant. O'Riely Auto Parts can order this kit you just have to specify diesel to get the correct fluid.

pyro2nite · 08-12-2012, 06:35 PM

If your temp was only showing 200 and the message center says reduce engine power, sound like a bad sensor. 200 degrees will not boil the coolant.

RLSmith · 08-15-2012, 05:27 PM

thats what i was wondering if it could be a bad sencor. my degas cap was replace when i was having all my coolant issues before. Its just strange to me that it only pegs out when it has some what of a load on it.

pyro2nite · 08-15-2012, 11:07 PM

Also, if the temp was high enough to have a CEl on, the fan should have been running. Was it?

sprayerjake · 11-01-2012, 02:05 PM

If the temp gauge maxs out then goes back to normal right away that is telling you your oil is getting to hot compared to coolant temp. This happened to my brothers truck last winter and thats what ford told him. The oil cooler ended up getting changed out.

broth · 11-02-2012, 07:26 PM

I lost an oil cooler on my truck as well but my coolant temp was never high just my oil temp. Maybe check out what your oil temp is at when it does this. Anything over 230-240 and you have a problem oil cooler wise. 200 on engine temp is not bad so it could be a sensor sending it into limp mode.

08-07-2012, 04:18 PM	#1
RLSmith Junior Member Join Date: Jan 2008 Location: Vero Beach Florida Posts: 79 Points: 13,569 Thanks: 24 Thanked 0 Times in 0 Posts	Coolant temp pegging out ??? I have a 2008 6.4 4x4 and while running down the interstate between 80-85 mph the coolant temp gauge pegs out and then it says reduce engine power. Slow down to 70 and it's fine. So I figured I wouldn't run that speed anymore but the other day pulling my airboat down the interstate it did it again and I was only going 70. The boat is light weight but it does hav some wind drag. Need to get tuis fixed before my next trip with my cattle trailer from Florida to west Virginia. I know it won't handle pulling thru the mountains. Looking for any advice. Thanks Ryan

08-08-2012, 02:10 AM	#2
Eazydeezy Let it all Ride Join Date: Jul 2007 Location: Denver, CO Posts: 1,306 Points: 30,859 Thanks: 178 Thanked 121 Times in 101 Posts	Is the truck stock or tuned? Have you noticed any coolant under (puking) under the hood. The first place I would check is your degas botttle cap. If the system is not holding pressure, it will cause the coolant to boil before the fans turn on. __________________ Dominic '12 PSD F-350 SRW Lariat Ultimate and chrome package, FX4, moonroof and nav.

08-08-2012, 09:31 PM	#4
Eazydeezy Let it all Ride Join Date: Jul 2007 Location: Denver, CO Posts: 1,306 Points: 30,859 Thanks: 178 Thanked 121 Times in 101 Posts	Try changing the degas bottle cap. It's a $5 part at any parts store. My truck was doing something similar and the cap fixed it. __________________ Dominic '12 PSD F-350 SRW Lariat Ultimate and chrome package, FX4, moonroof and nav.

08-09-2012, 03:18 AM	#5
neeltburn ADMIN/MAFIA Join Date: Dec 2008 Location: Evansville, IN Posts: 4,594 Points: 29,593 Thanks: 293 Thanked 650 Times in 566 Posts	I am not sure if the 6.4L has a similar Degas bottle but I know that some 6.0L Degas bottle cracked. You can rent a pressure tester from autozone I believe that have one that has the correct adapters. The other option is to do a hydro-carbo test on the coolant, it tells you if there are exhaust gasses in the coolant. O'Riely Auto Parts can order this kit you just have to specify diesel to get the correct fluid. __________________ When written in Chinese, the word "crisis" is composed of two characters. One represents danger and the other represents opportunity.- John F. Kennedy 2012 Ram 2500 Crew Cab Big Horn 6.7L 68RFE 4wd Yeah its stock. Edge Insight CTS / Line-X / Access Bed Cover B&W Turnover Ball THE RULES Support the Vendors who Support TDG 9-11-2001 NEVER FORGET

08-12-2012, 06:35 PM	#6
pyro2nite Senior Member Join Date: Dec 2008 Location: Sacramento CA Posts: 601 Points: 32,677 Thanks: 52 Thanked 64 Times in 63 Posts	If your temp was only showing 200 and the message center says reduce engine power, sound like a bad sensor. 200 degrees will not boil the coolant. __________________ 2008 FX4 3:73 ZF-6 SC SB Transfer Flow Singles club member 166 H&S Mini, KEM Tunes, S&B intake

08-08-2012, 06:11 PM	#3
RLSmith Junior Member Threadstarter Join Date: Jan 2008 Location: Vero Beach Florida Posts: 79 Points: 13,569 Thanks: 24 Thanked 0 Times in 0 Posts	Yes the truck is tuned with a sct livewire. No custom tunes just canned tunes. It stays on max setting. I also have a aftermarket intake and I have deleted the burner. Just a straight pipe exhaust. I'm not losing any coolant anywhere and both egr coolers were replaced about 16,000 miles ago along with head gaskets all under warranty an while truck was still stock. As soon as the needle pegs out and it says reduce power you let off the pedal for about 15 seconds an it will drop right back to regular temp. I had my live wire plugged in to watch the temp and the hottest I seen was 200. It runs around 194 to 196

08-15-2012, 05:27 PM	#7
RLSmith Junior Member Threadstarter Join Date: Jan 2008 Location: Vero Beach Florida Posts: 79 Points: 13,569 Thanks: 24 Thanked 0 Times in 0 Posts	thats what i was wondering if it could be a bad sencor. my degas cap was replace when i was having all my coolant issues before. Its just strange to me that it only pegs out when it has some what of a load on it.

08-15-2012, 11:07 PM	#8
pyro2nite Senior Member Join Date: Dec 2008 Location: Sacramento CA Posts: 601 Points: 32,677 Thanks: 52 Thanked 64 Times in 63 Posts	Also, if the temp was high enough to have a CEl on, the fan should have been running. Was it? __________________ 2008 FX4 3:73 ZF-6 SC SB Transfer Flow Singles club member 166 H&S Mini, KEM Tunes, S&B intake

11-01-2012, 02:05 PM	#9
sprayerjake Junior Member Join Date: Jun 2009 Location: Vegreville Posts: 23 Points: 3,550 Thanks: 1 Thanked 2 Times in 2 Posts	If the temp gauge maxs out then goes back to normal right away that is telling you your oil is getting to hot compared to coolant temp. This happened to my brothers truck last winter and thats what ford told him. The oil cooler ended up getting changed out.

11-02-2012, 07:26 PM	#10
broth Member Join Date: Jan 2009 Posts: 278 Points: 15,199 Thanks: 33 Thanked 10 Times in 10 Posts	I lost an oil cooler on my truck as well but my coolant temp was never high just my oil temp. Maybe check out what your oil temp is at when it does this. Anything over 230-240 and you have a problem oil cooler wise. 200 on engine temp is not bad so it could be a sensor sending it into limp mode.

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