I have a 95 4wd auto blazer that had the famous rusty radiator fluid. The whole system has been flushed numerous times, new radiator cap, lower hose, Thermostat, waterpump, and fan clutch. I have also checked the cat for blockage, and bypassed the heater core. Runs great and does not leak any antifreeze, but when I drive any long distance it will slowly overheat, but usually only when its working a little harder like climbing hills or on really hot days. Since I drive most of the day at work in the hills of pitt this is a major problem for me. Everything seems to be operating fine and seems to be circulating well. I hope someone out there has experienced this same issue and can help me figure out what the heck is up with this thing.

 

Is the radiator clean? Maybe take the top support off and see if you can look between the condensor and the radiator. I've had that half full of leaves and bugs on one of my other vehicles. Also when you start the engine up COLD, maybe pull the radiator cap and watch the coolant. It should appear to circulate. You will also be able to notice any harsh bubbling from something like a head gasket issue. **Keep an eye on it because it will heat up and begin to overflow very quickly.**

You may also attempt having the ignition module tested to make sure the timing is stable and correct. After that maybe verify timing with a light.

 

Yes , the trash collector between the radiator and condensor has been cleaned thoroughly. I've started it w/o the radiator cap on and there was definately good circulation. Also the engine oil is very clean, no foamy residue, or anything. The engine is running smooth, so I don't think it's a timing issue but, who knows. Might be worth checking out at least. Thanks

 

Here's some food for thought. How's your EGR valve? The EGR sends "cool" (in reality, its hot) exhaust gas into the intake to cool the cylinder heads, to reduce emissions (NoX). If the EGR is blocked, or full of carbon, it can't cool the cylinder heads, and may cause your overheating issue. The EGR is a cylinder looking module at the front most part of your engine, between the cylinderheads, on the intake. Two size 10 bolts are holding it in.

-OSS

 

Helped a friend with his 98 similar deal. Replaced the usual parts you did. Turns out the radiator it self was bad, mind you this thing passed 2 pressure check with no problems. Changed radiator, over heating gone.

 

The problem is you can't see the circulation any lower than fluid level. Anything below the very top there is unknown and a best guess can be made with an infrared heat gun. Considering gravity takes over when it comes to gunk in a tank, the lower 1/3 or more of the radiator could be plugged and you'll never know it without taking it apart. No more expensive than a radiator is, why not go ahead and change it before you cause real damage?

 

Thanks guys. I appreciate the help. going to get a radiator and see what happens. Wish me luck.

 

Radiator did it. Problem solved. Food for thought. If you ever need to check for gunk in the bottom of your radiator,run it till it gets good and warm then let it sit for asbout 45 min. After it cools run your hand down the radiator. The top section that flows freely will be good and cool, but the bottom where it is all gunked up will still feel warm. Wish I'd have known that about a week ago.Lol. Discovered that when I pulled the old one out. Thanks guys for the input, I really appreciate it.