On Friday I was driving in stop and go traffic as usual and the ambient temp was around 105 degrees... normal for here. I heard the fan come on so I looked at my temps; coolant and oil were about 220 degrees and transmission temp was around 200.The fan cooled the temps down a bit plus I drove on a flat road without too many stop lights which brought the temps back to normal readings; EOT, ECT around 200 and tranny around 180. The same thing happened on Saturday but this time no fan. the EOT got up to around 225-230 and coolant around 220-225. Transmission was a little over 200. These temps seemed to rise all of a sudden and not gradual. I took the truck on the freeway and the temps dropped pretty quick back to normal ranges... still no fan. When I pulled in the driveway I noticed coolant dripping from under the drivers side wheel well, thats when I noticed the leak from the reservoir. Saturday night with ambient temps around 95 I was driving on the freeway and the temps were just fine. This morning driving to work (on the freeway) EOT and ECT were right around 200 after a 20 minute commute, after I parked the truck I unscrewed the cap off the overflow (rather quickly) and it *popped* with some pressure. I haven't had any puking or loss of coolant (other than after the small leak started), no wrench light or codes (no impending codes either). The wires and connector at the top of the fan shroud appear fine. Does the pressure rise in the cooling system as the coolant temps go up? No oil or diesel in the coolant either. Any help will be appreciated, thank you.

 

Fan should kick up at about 210 ECT and kick down at about 195 ECT. Check for Electric Fan Clutch: No Signal (PCM not reading fan RPM), I don't remember the code, and a second code for the fan clutch. Both codes showing could mean your EFC is failing or more common, the pig tail has come loose from its mount on the engine fan shroud, top right of shroud looking from front.

Inspect connector at that point to ensure it is tight, and pins, sockets are clean. Remove top shroud cover to be able to look at the fan clutch harness. Inspect for evidence that the harness has come in contact with the fan. Damage to the harness would prevent the fan from kicking up and down with temperature.

I have an intermittent code for no signal. Fan clutch recieves signal to kick up and down but does not talk to the PCM to tell what RPM the fan is running at. Sounds like your fan clutch isn't getting the signal to kick up with temp.

Check spring clamps at hose connections. Replace spring clamps with stainless steel screw type hose clamps as necessary.

If degass is cracked (this has happened before), remove and replace it. Do check for smooth cap rim, no burrs or chips.

Eric

 

Also check coolant level is set to 1/2 inch below minimum level mark.

 

Thanks for the reply, coolant level is fine... just a hair below the min line (new overflow with the updated sticker). I will take the shroud off when I get home and check the wires leading to the fan clutch. It was odd how quickly the TFT, EOT and ECT temps rose on Friday before the fan turned on... it was as if the coolant stopped flowing.. stuck thermostat maybe? I thought water pump but when I got home I took the cap off the degauss bottle and saw coolant flowing from one of the small hoses. Another thing, the fan doesn't spin freely (with the engine off of course...lol) it has some resistance to it... does that mean anything? I replaced the thermostat last year when I did a coolant flush so I'm thinking I may put the old thermostat housing in without the thermostat and see if I am still having issues. It's evident the fan isn't working correctly but I'm thinking something else is wrong too. Again thank you.

 

Also, I scanned it for codes and didn't get any.

 

Cooling system pressure will indeed rise with temperature, it should be regulated at 16 psi. The coolant reservoir is fully pressurized, it can be quite dangerous to simply remove the cap when the engine is warm and the cooling system is under pressure. The coolant can explode out of the filler hole and burn you pretty badly.

Brian

 

Any chance you've cleaned the radiator, condensor and IC air passages with mild water pressure lately?

Could just be plugged enough to not pull enough air @ low speeds/idle.

You'd be surprised what gets trapped in there.....do not spray it with high pressure you'll definitley bend the fins

Ofcourse the degas crack is an obvious but check out the air flow

 

Yes, I sprayed all of them yesterday, had a large moth on the lower cooler...lol. They were actually pretty clean. I'm stopping by the dealer on the way home and picking up a new Degauss bottle ($89), seems like an ok price. Other places online have them for around $70 plus 20 shipping. Should I l hold off installing it until I get the root issue resolved? The leak from the current degauss bottle is slow plus I have 2 gallons of coolant (50/50 mix) in the toolbox. Thank you.

 

I remember the old days when coolant would spew out the radiator like a geyser... lol I was watching the coolant close to see how rapidly it was rising as I was turning the cap. Thank you.

 

just a bit of useless information. 1 psi of pressure = 3*f change in boiling point of coolant

so a 16 psi cap would rasie the boiling point from 212*f to 260*f

a leak in the cooling system you might as well not have a cap

 

Your coolant degas system pressure will not typically run at 16 psig. It will only run as high as the pressure increase from the liquid expansion (with heat) will take it. The liquid expanding will compress the vapor space in the degas bottle. Normal pressures will be 8-10 psig when hot.

Also, removing the cap on the degas bottle is a LOT safer than when we had radiator caps in our vehicles. This is because the radiator was liquid full (incompressible fluid). With our systems you will be releasing a gas - do it slowly and it should never allow liquid to escape. Still, take caution when removing the cap ......... the liquid level will rise when the pressure is released.

 

Listen to these two men^^^^ or in bismic's case super computer....they know what they are talking about

 

Thank you for all the replies! The ambient temps driving home this afternoon were just under 110, which was a few more degrees then the 2 days I had issues. The ECT and EOT were fine (normal for here) right around 200. TFT was about 180. I purposely drove on surface streets in stop and go traffic.. no issues so I went home and changed the degauss bottle. The broken one, that was replaced back in 2007 was golden color on the bottom, the new one is white/clear in color. Easier to see coolant now. Anyway what I did yesterday was unplug the connector on top of the fan shroud and used electrical contact cleaner on the male parts. I also sprayed the radiator/coolers with the hose to clean them even though they were pretty clean. I pulled of the "Powerstroke" plastic piece on top of the shroud and could see the connector to the clutch. It was fine.. When the engine was running the center part of the clutch that the wire is connected to was wobbling a little... is that normal? After everything was back on and coolant topped off I took it for another spin on the surface streets... no heat issues at all. It ran normal. ?? Weird. I'll keep and eye on it over the next few days and see what happens. Again, thank you for the replies and help.

 

Ahhhh, so that tiny leak may have been the culprit, well I have the new reservoir on, so far so good. By the way, JB Weld almost plugs the crack... almost...lol. I just finished a box of Cheese Nips, I prefer Cheezits but the Nips were $1.88 for a 12oz box at the new Winco foods by my house...lol Thank you for that useful info! It made perfect sense.

 

your welcome.
to simplify it more a cooling system operates about the same way a pressure cooker does.