88 Suburban over heating stumps all

[jcphphy]

Originally Posted by 84fiero123

replace clutch fan with regular. if that doesn't wprk remove thermostat.

Try to do what 84fiero123 suggested, or try this, take of the thermostat and try to drive it and see if doesnt overheats, if it does check the water flow

[redwheeler]

did u change anything on the front of ur truck valences grills brush guard any thing if the air flow is changed it will over heat

[joelseeley]

Hey, put a supercool radiator in there. they make them for the diesel suburbans, it will fit, guaranteed not too overheat then

[Ryan685]

Once a thermostat has gotten hot, it's bad. A wax pellet inside the thermostat expands and opens the thermostat. When it gets overly hot, the wax leaks out and the thermostat will not be able to open as far as it should. What caused the initial overheating in the first place could have been a bad fan clutch or a clogged radiator. I'm not sure how the garages could have checked the head gasket but it sounds good..... Radiators over five years old don't cool as well. Make sure the fan shroud is still in place.

[Jeff406cid]

This post has been around awhile but I just came across it, so in the intrest of helping anybody with a similar problem in the future:

I there is a pocket of air trapped in the cooling system it will cause violent temperature fluctuations. The temp can rise to extreme heights only to magically come crashing back down to below normal temps, only to repeat the cycle. ususally in cold weather it's more pronounced, in warmer weather less so.

I had this very same problem and suffered with it for years. Only after working on later model vehicles that have air bleeds in the systems did I finally realize what was going on. If any part of the cooling system is higher than the pressure cap, it will cause air to be trap. This can be as simple as a radiator hose, whose curve is above said radiator cap! As was the case with my car!!! This is also why a pressure test doesn't reveal this problem. All that it took to correct the problem was to push the radiator hose down below the level of the pressure cap and vent it. This in effect purged the offending air and returned steady temps for me to enjoy! To permanently correct this, turn the radiator hose, or get the correct one, or find the cause of air to ge trapped in the system.

Hope this helps.

[Elbert]

IF all the parts have been repalced as you say and they are correct. THen I would look at the radiator fan clutch. THose metal radiator fans seldom wear out...but the fan clutchs do wear out over time and miles. I too wonder if it has the correct water pump? If the head casket is ok and no-one suspect a cracked head or cracked block. One assumes the thermostat is installed correctly? How many miles on truck? So it passes the pressure check with no problems? IF my truck I would be tempted to replace the waterpump myself to make sure its the right one. Trucks with the serpatine belt (large single fan belt that drives all the accessories) take a different water pump than those with the old style mult-belt setup. I beleive that year model truck was one of the first with the serpatine belt system? Car repair shops should know this.

DO a simeple check yourself..... Engine cold, open radiaotr cap and check fluid level, make sure full or and inch or two full from radiator top. Start engine and leave radiator cap off. Monitor guage and coolant flow throug radiator....when truck reaches operating temp you should see the coolant flow increase when the thermostat opens (verifies the thermosat operation) and also water pump operation.... you should be able to feel air being pulled across the radiator fan. Take a look at the radiator fan to make sure its moving properly and you don't notice it "wobbling" around.

When truck is hot and you driven it...do you ever hear the fan clutch engage? you 'll notice this by the large increase in fan noise when you start from a dead stop or at slight increases in rpm at lower speeds. At higher speeds and higher rpm level its a little harder to determine when the fan clutch engages. YOu ususally feel a little power drop in the engine too, when the fan clutch engages.