My vehicle:
2001 GMC/Chevy 3500 'Express RV' Van
Vehicle is a 21.5' motorhome manufactured by R-Vision/Trail-Lite
Current mileage: 49,300
5.7L Vortec V8 engine
4-speed automatic transmission
4.10 diff ratio / dual axle
DESCRIPTION OF PROBLEM:
From June 2001 (new vehicle) to July 2009 (8 YEARS), when driving up a long hill and the temp got close to 1/2 (at around 205(?) Deg F.) The fan clutch would engage.
SINCE THE RADIATOR TANK AND END-TANKS WERE REPLACED ON 7/16/2009, and WHEN DRIVING UP A LONG HILL, the FAN CLUTCH DOES NOT ENGAGE UNTIL THE TEMPERATURE GAUGE REACHES 3/4, at around 235(?) Deg F.
It shuts off when the temp is just above 1/2, at around 210(?) Def. F.
The truck's temp gauge shows 160 deg F. As the low point, 210 deg F. As the half-way point, and 260 def F. As the max.
The normal running temp on the truck is between 1/4 and 1/2 on the temperature gauge, usually just above 1/4.
THE THERMOSTAT AND FAN CLUTCH HAVE BEEN REPLACED AND THE PROBLEM PERSISTS.
The latest opinion by the shop that replaced the original radiator is that I should try a COOLER THERMOSTAT. But I am reluctant to deviate from
Vortec (GMC's?) Original specs on the engine's optimal running temperature since the vehicle's
computer expects the engine to be running within that temperature range. Furthermore, UNDER NORMAL HIGHWAY DRIVING CONDTIONS (NO HILLS) THE
THERMOSTAT WORKS FINE AND THE TEMPERATURE IS NORMAL; THERE ARE NO PROBLEMS.
- At what temp is the fan supposed to engage? Around 220 deg F? At around what temp should it disengage?
- Will it harm the engine to go up to 235 def F. (3/4 pt) as long as the fan clutch brings the temp back down to around 1/2?
- Why would using a cooler thermostat help? When going up a long hill with the engine/coolant hot, the thermostat would be wide open anyway. What I need is for the fan clutch to engage at that point.
ITEMS REPLACED SO FAR:
- Aftermarket radiator tank and end-tanks that match GMC's specs for size/capacity; bottom-radiator hose, radiator-cap
- Coolant: was refilled w/ 50/50 DEXCOOL/water
- GMC thermostat (original specs: opens @ 195 deg F.)
- GMC fan clutch (matches original specs)
The cooling area of the radiator was cleaned to remove dead bugs, etc.
A DIAGNOSIS WAS DONE @ 2 DIFFERENT SHOPS AND 1 GMC DEALER:
- there are no leaks in the cooling system
- under normal conditions (no hills), temp is normal
- performed engine block test; everything normal (head gasket, etc.)
- the coolant/thermostat/radiator is circulating/cooling properly
- their OPINION (and mine also) is that the temperature gauge and sensor are functioning properly
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Sunday, September 6th, 2009 AT 1:13 PM
