My 93 4.3 runs warm for some reason. It runs at about 220 - 240 at all times. It has a new waterpump, flex fan (no clutch), temp gauge sending unit, thermostat, and fresh coolant. It used to get up to about 260 and the check gauges light would come on and it would cool down to 220 - 230 very fast. I figured it was a the thermostat that was replaced in August so I replaced it again and now it doesn't do that check gauges light thing anymore but still runs warm. Before I changed the thermostat the radiator and cap were always cool to the touch but the coolant in it was alway semi hot, not really hot but semi. I haven't checked since I changed the thermo I'll do it soon. Someone suggested to me that there isn't enough presure in the cooling system but that would mean a leak and it doesn't leat and the coolant level statys where it is at all times. What I think it might be and this is far fetched but when I bought the truck, I did my routine, all new fluids and all small maintenance and when I changed the thermostat for the first time there was green crystally stop leak junk all over it. Could this insulate the radiator and limit it's cooling ability?
I had problems with both of my 4.3 blazer's (past and present) I had done the thermostat, radiator cap, etc.. I finally had my radiator flushed, and tha seemed to do the trick. Just my 2 cents.
Good Luck no one likes to see 240 on there temp guage, I now I don't!
<font face="Comic Sans MS"> On that new thermostat did you make sure to drill a hole in the flat part? I think it should be a 1/16 to 1/8" in size. It's purpose is to let air out of the system. Air insulates the thermostat and prevents it from opening until the air is the temperature that the thermostat is supposed to open at. Also, that flex fan isn't necessarily the best item for several reasons. First reason is that it's completely useless when the engine is revving up even if you're driving at low speeds. That can cause it to warm up on the trail. Another reason is that if you happen to get into somewhat deep water and it hits that fan it's likely going to cause that flex fan to bend and scrape the radiator. How long did you run it at 260°? Hopefully not long and not many times.
When the guage is reading hot, go out and feel the upper radiator hose. If it's cool/cold then you have a sticking thermostat or air pockets getting trapped between the thermostat and the coolant. If it's hot then the problem is elsewhere.
Have you checked up your temp gage or sensor. because if you ran it for a long time at high temp (like 250-260) and the engine still runs good, the engine might be at the right temperature but have a bad sensor or gage. Otherwise, you're gonna start having problems if you keep running it like that. I had the same problem on a 350 and had a valve job to do after running it high like that [img]/wwwthreads_images/icons/frown.gif[/img]. And it can get worse if you run it a long time (complete rebuilt[img]/wwwthreads_images/icons/crazy.gif[/img]).
Have you checked your timing. The timing of a vehicule might make you run hot like that if you got too mutch advance. Drag racers like that [img]/wwwthreads_images/icons/smile.gif[/img] but then again, they only use there motors for few minutes and rebuild them again afterwards [img]/wwwthreads_images/icons/wink.gif[/img]. Hope this helps
1999 Zr2 4.3L 31x10.5 BFG M/T's
Stuck in the snow
(figuratively speaking of coarse[img]/wwwthreads_images/icons/wink.gif[/img])
Tomorrow I have the day off so I'll warm it up, check the uper radiator hose, drill the hole in the thermo, and if that doesn't work I'll make an apointment to get the timing checked and flush the cooling system. It might be the timing now that I think of it because I did remove the cap, mark it, and reinstall it. I thought I did a good job, it doesn't backfire and idles at about 700-800rpm (so says my cheap $40 tach). I'll let you guys know what was wrong sometime tomorrow.
I drilled the hole into the thermostat and that seemed to do the trick. It ran cool at about 190-200 and then after driving for a while it gets to about 220-210 and stays. It rarely gets hotter now. I guess my only option now is a flush. We'll see what happens now.