Here is the situation: 1995 4dr 4x4 4.3L automatic A/C When I drive with A/C off temp runs just below 210. When A/C turned on temp creeps up to 235 (think it's 235, big mark between 210 and 260) when I get into stop and go traffic. After getting back up to highway speed i.e. 65 it takes a long time to get back down towards 210 (sometimes it never does) What has been done to fix problem: New Stant 195 thermostat (2x), system flushed 2 times using Prestone back flush kit, new water pump, new fan clutch and new serpantine belt. All idler pulleys seem fine. Only thing left is radiator. Is there any difference between Stant thermostat and GM unit? i.e. does GM unit have a bleed hole? Any help appreciated as I sure don't want this thing to go into full blown overheat while driving family to Ocean City over the Chesapeake Bay bridge.

 

In all of that replacing of parts, did anyone ever suggest just cleaning the exterior of the radiator? I know I have to do this on a yearly basis or the bugs plug up the condenser, making for the exact same issue. I would remove the upper fan shroud and take a garden hose to the radiator and condenser. Soak it down really well and let it sit for a bit, then really blast away at it until you get water shooting through the condenser pretty evenly over the whole surface of the radiator.

I actually made up a little wand out of some flexible copper tubing with a fan nozzle on the end of it. If you have a power washer, leave it in the garage, you can destroy a radiator with that much pressure. The pressure from your garden hose should be sufficient to clean it out.

Hope this helps!

 

Swartlkk,
When I had it apart I did blow through the radiator and condensor with compressor. I will try giving it the hose job.
BTW I had family in Waterloo (grew up in Rochester). Used to go there for family picnics in the summer.

 

Ok, I just always think to clean the exterior of the radiator first as it is one of, if not the most, overlooked aspect of the engine cooling system. And it's relatively cheap and easy to do.

Yeah! I grew up just south of Waterloo in Romulus, but my cousins were in Waterloo.

 

This is a good thread because I just replaced the water pump and fan clutch on my 99 4.3 2WD last night. I was concerned because it runs normally just under the 210 mark but has never gone over. Is just under 210 wher it should be? My K-5 has always run at the 1/4 mark. So am I just paranoid?

 

Well, the problem is solved. New radiator did the trick. Now it stays below 210, usually on first small mark before 210 (I think it's about 195). I've attached a picture of the Trans cooler, cooler fill, exit to engine side of the radiator. I have others but, this is probably most dramatic. This Blazer has never had DexCool as far as I know. It had green when I got it as a used vehicle. A little other background: a couple of years ago the trans cooler split putting water in trans and trans fluid in cooling system. I did a flush at the time before replacing radiator but, not good enough. I remember shortly after replacement I was seeing oil residue in recovery bottle again so I did a quick flush again. (I now have one of the Prestone backflush kits on it which does a better job of flushing it out). I tried putting a light at the other end of the cooling tubes and only the top 5 or 6 were clear, didn't see any light through most of the lower ones. Lesson learned: if you get a major contamination of cooling system use back flush kit, good cooling system cleaner and flush, flush, flush.
Thanks to all those that offered assistance,
Dave
p.s. to swartlkk my last duty station was Seneca Army Depot

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