Normal Running Temps?

[WRB Diesel]

Last summer on a trip to Bend, OR I had an overheating problem when going up a steep grade outside of The Dalles. The AC was on, and EGT were ~ 1,000, temps got to 250 pretty quickly and we pulled over, let things cool, turn off AC and continue on. The rest of the summer when travelling over the pass in WA (mild grade) temps seemed to get up to 210 - 220 pretty easy without AC on. Now that summer is in full effect and I use the Burb to travel over the pass to eastern WA every week (yah, I finally got a job after 5 months of searching) where the temps are 95-105 in the summer, I want to be able to use the AC and keep up to speed. I assume I should not have any problem with operating temps becuase I am travelling with no load, just me and maybe two dogs. I have a 3" DP, 4" exhaust, high flow air filter so EGT's never really get above 950 when travelling around 65-70mph. I also have the dual thermostat, High flow water pump, and just before the last trip over the pass I installed a new radiator, all additional coolers and spaces between are cleaned every spring so air flow is not a problem. What I notices yesterday on my way home to western WA;
65mph on flat ground, EGT 600-700, AC on temps around 195-200. As soon as I would hit some short grades here and there temps would creep to 210 then back down to 200 once things leveled off. On the down grades while coasting things seem to cool off to 180 pretty easily (dual 180 stats). My concern is that with the upgraded cooling system in place and no real load should my temps really be varying this much. I guess I assumed that with the new radiator I would see temps stay around the 180-190 ranges. Am I being overlly cautious or am I seeing normal operating temps?

Thanks

[rustyk]

A couple of things to check would be the lower radiator hose - water pump suction can cause a partial collapse of an old hose.

The thermostats also would be suspect, and they're easy to test.

Another thing to check is the air filter. I don't know the grades you're climbing, but I just got back from a trip in my 8 ton motorhome, where it ran a 5-mile, 9% grade at 850°F EGT and 12 psi boost with OAT at 92°F, coolant temp, 215°F. Normal level cruise @ 65 mph is 500°-550°F, boost @ 4.5 psi.

Obviously my engine's different, and the radiator on my diesel pusher is enormous, and other folks with more equivalent trucks can be of more help, but the hose, thermostats, and air filter are pretty generic.

[DaveNY]

At 65-70 My EGT will be at 400-450 tops and boost around 5-6 bs Temp gauge never moves. Start checking for air flow between AC condensor and radiator or intake air. Sounds like something is clogged up?
Dave

[JohnC]

How's the fan clutch? My '95 used to run up to about 230 then the fan would start roaring and it'd come back down to 200.

[WRB Diesel]

Dave - airflow is good, when new radiator was put in I took the oil cooler down and blasted everything with air, some water and more air and got things pretty clean.

Rusty - Best way for checking stats is to remove them and run with no restrictions to see if they are not allowing the proper flow, correct?

John - I believe the fan is in ok working order, I am assuming my clutch is old and worn but the fan is always on pulling some pretty good air through the coolers and rad.

I think the termostats could very well be the cheap low flow 180 stats when I purchased the upgraded cooling package, do no remember if I took a real good look at them to make sure there were either the robertshaws or GM high flow stats.

Thanks

[a5150nut]

Instead of running with no stats, pull them out and drop in a pan of water and heat until they start to open and check temp with a thermometer. :D

[rustyk]

Instead of running with no stats, pull them out and drop in a pan of water and heat until they start to open and check temp with a thermometer. :D

Exactly. No sense opening up the housing, removing the thermostats, buttoning up, opening again, reinstalling, buttoning up, and it's not a good idea to run with no 'stats.

And running with no 'stats generally won't indicate if they're bad or not.

[DaveBr]

I'm thinking it's your clutch fan getting old. You also may have an old 5 blade fan. I upgraded to Kennedy diesel's 180 calibrated clutch and 9 blade fan. I run a single 180 T-stat and custom 5 core rad. I never go over 210*pulling. I know I should upgrade to dual T-stats but the system works so it is a little lower on my to do list. You should be able to tow with air on with these upgrades and what you've already done.

[JohnC]

... I believe the fan is in ok working order, I am assuming my clutch is old and worn but the fan is always on pulling some pretty good air through the coolers and rad....


If the water temp is up to 250 and there is not a NOTICABLE change in the ROARING noise from the fan, then it ain't workin! First time it happened to me it was saying "what the he|| is that!"

[WRB Diesel]

Yeah, I have never fully seen the workings of a new or well callibrated clutch and fan as all the GM trucks I have owned have been hand me downs or purchased with high miles. With a new clutch, does the fan turn at all, just slightly, or is it moving pretty good and then takes off when the clutch kicks in? This weekend I have got a long list of vehicle repairs, T-stats on this rig along with rear drums, shoes and seals. Then the '96 Tahoe needs a new fuel pump (gotta love the design of the fuel pump is the gas rigs, this will be the forth pump in 200K) plugs, wires, cap and new o2 sensors. Then the '90 GMC work truck needs need head gaskets at a minimum because the block heater fell out with a crew in it on the way to a jobsite and overheated. And to top it all off the garage door came out of the tracks and is jammed.

I post what I find out with the stats

Thanks

[DmaxMaverick]

The fan clutch should begin to engage, and be fully engaged (fan turning at engine speed) within a few seconds of thermostat opening. It shouldn't "spin up" too slowly. It should also be engaged (noisy) during most cold starts, and remain engaged for a couple minutes before disengaging. If the engine is hot (above thermostat temp), and you can't hear the fan at mid to higher RPM's, either the clutch, stat, or radiator is bad. Most often, it's the thermostat(s). The fan clutch reacts to the temperature of the air passing through the radiator, which is controlled by the stat(s).

[JohnC]

My experience is that it will not engage until the radiator temp climbs noticeably above the thermostat setting. It is noticeable on a cold day when the RPM's are up around 2000, although it's not actually "engaged" then. It locks up for a different reason under those circumstances.

It's sort of like a "lock up torque converter". Under normal circumstances it drives the fan with some (a lot of) slippage. When the clutch "locks up" it's pretty much direct drive. If you've never noticed it, it's not happening.