Motor Getting Hot

[Justin Fleming]

So last night I notice that when driving down the road for about 10 minutes at 50ish I noticed the temp gauge creeped over 210, so I pulled into a sub division and drove around and it came right back down around 180. Got back on the road and with in 10min it was up or 210 again. I pulled over and it appears that everything is in tack, both heater core hoses were hot, cab was blowing hot, there was reserve fluid in the over flow bottle, belt connected, no known leaks etc.

Do we think possible thermostat sticking, possible fan issue, etc

any thoughts....

 

[scottystills]

Fan, fan clutch, water pump would be my first targets.

 

[dyeager535]

I'd say probably a sticky thermostat, cooling at 50MPH should have nothing to do with the fan.

210* is nothing to worry about. Most thermostats now are pretty much junk in terms of out of the box working right (even high end aftermarkets aren't a guarantee), unless it gets worse I'd probably not worry about it.

Does it do it at any other times, sitting idling, etc.? Could be an airflow issue, not a bad idea to check the radiator fins to make sure they aren't all clogged up (especially if there is an AC condensor in front of it). Still not as likely as a sticky thermostat.

 

[Justin Fleming]

The only thing that worried me is that the truck always runs at 180 and to see it jump over 210 was kind of a red flag. Radiator and condensor are new within the last year, does not seem to be a issue at iddle. I really dont drive the truck much so I am not certain what happens if I were to drive it for say 1/2hr at 50ish, my assumption they way the needle keeps creeping is that it would over heat....I guess I should also at the it is only 20 degrees in michigan at this time...

 

[6.2Blazer]

As mentioned above, the symptons of getting hot at higher speeds and cooling down with slower speeds and stop and go driving should eliminate anything related to the fan. You haven't been out in the mud recently have you? Is the truck warming up in a reasonable amount of time when you first start it? A thermostat that was stuck halfway open could cause this condition, but you would probably notice the truck taking longer to warm up also.

 

[dyeager535]

Ahh. If you stopped to keep it from climbing higher, then you've probably got a real issue. I'd let it go higher if it will, at least a bit to confirm it won't stop climbing. I understood that it just got to 210* and stopped. Cooling fine at idle should indicate the fan/shroud are ok.

Never dealt with a blown head gasket, perhaps someone can clarify how that would act. Seems a bit odd that removing the load on the engine lets the temp go back down, I'd think a stuck thermostat would tend to stay stuck. It's obviously closing if the temp doesn't go real low.

 

[skunked]

I have the same issue with my truck if I go over 50 mph, whole cooling system is brand new.

I'll be checking the thermostat first it sounds like.

 

[diesel4me]

I've seen the lower radiator hose get sucked shut at high rpms or speeds and cause overheating...most had a spring inside them to prevent that,but some dont,and if you dont transfer it to the new hose from the old one,that can happen..if the hose is old it might be collapsing inside and blocking flow at higher speeds or revs too,even with a spring..

If the water pump is old,it might be losing it's ability to pump--seen the impellers rust away,or come loose on the shaft and free wheel at higher speeds..

Usually a blown head gasket will make excess pressure in the radiator and make the upper hose swell up like a balloon...but a slight leak might just put air in the water and make it foam up and less efficient at cooling...
The thermostat is the cheapest thing to replace first..I'd try that and see if it improves it any..

 

[dyeager535]

Spring is there so they could vacuum purge/fill the cooling systems on the assembly line without requiring the engine to run.

System is pressurized, I've yet to see one suck shut. I hear they can, I've not seen it, nor do I understand how it's possible. If there is a flow restriction anywhere (such as the thermostat being closed) there is no way to generate suction, as the fluid can't go anywhere.

Perhaps with a failed radiator cap? My lower radiator hose is solid as soon as the engine starts, hot or ice cold.