I know it's said that a 15+ degree delta is bad news. Mine have been ranging from 7-13 so far this summer. Should one always expect the coolant to be lower than the oil? I figure since it flowing through the radiator it should at least be a couple degrees cooler. What are you all seeing?

 

Until the engine is fully warmed up, the coolant is usually hotter than oil. Once your coolant reaches 190 (assuming properly working tstat) the coolant will stay about 190 and the oil will catch up and then go hotter.

The 15* test is done at cruising speed 65-ish on flat hiway not towing for 15 mins, ONLY after temps are 190.

Sent from my Sprint PC36100 using IB AutoGroup

 

Ok! I've got some flat terrain coming up once o get out of this construction area, so I'll give it a test. So if my coolant was 190 and the oil sat consistently at 205+, that is indicative of a failing EOC. Right?

 

Sounds like a partially clogged oil cooler.. doesn't mean immediate doom. Originally the spec was 20*.

You should also verify your oil and coolant temps read close to each other after sitting for a day or two. Compare them to the transmission temp in the AM before you start. You want them to be "close" depending upon your overnight temperatures they might not be the same as ambient temp, but they should be 1-2 degrees apart (oil, coolant, trans) thus giving you some confidence the oil/coolant sensors are accurate.

 

Alright. What's interesting is that my Transmission Fluid Temps have been no higher than 165 during this entire trip. Perhaps I'm reading the wrong PID? Can you remind me exactly how the thermostat works again? It's activated after the coolant or oil temp reach 190?

 

In the summer heat, the sat SHOULD be running @ 190-194 with no load.If your going lower than 190 running and have higher than usual deltas your sat maybe weak and that is what makes the oil temps higher.........understand?

 

Your coolant Tstat will start opening at around 192*f. ECT

Your tranny also has a Tstat in it. And it opens at about 172*. If the trans temp is below this, the Tstat will still let about 10% of the fluid to still go to the trans cooler. There fore your tranny will still be cooling fluid. That is why you will read 165* tranny temps.

 

Ah, ok. My coolant temps range from 186-196 during a a usual trip down interstate with no load. Oil is 198-205 on that same trip. Temps are nearly identical at idle. If I had to guess, I'd say it's a weak thermostat. Oil cooler is new as of 2 years ago when it and the EGR were replaced. Would it make sense to go ahead and swap the water pump while I'm working on the thermostat?

 

I'd replace the stat with a FOMOCO one and go from there,sounds like the same problem I'm having right now.I'm due for a coolant change and flush, just need some time to do it

 

Absolutely! Time to google videos on replacement of the tstat. I'm in the exact same boat, coolant is pretty new (final charge), but I need the time to change the tstat and perform a full flush with VC9.

 

So, if ECT (Engine coolant temp) was 196 at the same time your EOT (Engine Oil Temp) was 205 you are 9 degrees apart and that's fine.

My TFT temps runs 156-165 most of the time on the hiway also.

 

Yeah, but the ECT is usually sitting lower. I had to push pretty hard to get it above 190, which makes me feel like the tstat isn't letting coolant into the block. Since it is one of the parts most likely to fail and i'm nearing 200k, I might as well
go ahead and change it for peace of mind. Along with the serpentine belt.

http://www.powerstroke.org/forum/6-0...placement.html

 

Gotcha, many 6L struggle with even a 3 month old T-stat for some reason.

 

I would not flush anything with a 9 deg delta. The flush will break loose stuff in the cooling system all at once and plug your cooler. I would drain in a clean bucket enough to change your stat, and install a coolant filter at the same time.

 

X2 on this, mine was at the same level ,did the flush and started seeing over 25 deg diff that little flush cost me 2300 in new EGR and oil cooler part of $ was the external coolant filter, save your penny's up for the big move ( Bullitt proof ).