Hello everyone,

I recently bought a 2000 GMC Jimmy 4.3 Vortec, 127,000 miles. The car ran great for about a week, then suddenly started to run hot (around 240 and was still rising). I noticed that while the car is running, neither of the two radiator hoses are heating up or getting hard as if they have no coolant running through them AT ALL. There IS coolant in the cooling system. I replaced the thermostat thinking that it was stuck closed but that didn't fix the issue. Anyone ever experience something like this before? Can my radiator be that clogged all of the sudden? I read somewhere that a bad radiator cap can also cause the coolant not to flow, but I'm not certain how accurate that is.

Noteable facts;
No coolant mixed with the oil
No leaking coolant or coolant smell
Fan is turning on

Thanks in advance for your help!

 

Possible bad water pump? The impeller could be broken off causing no water flow?? What color is the coolant...as in muddy looking from a clogged/clogging radiator?

 

The coolant is brownish.. and does look a little muddy. You really think it could be THAT clogged though? I would think the car would slowly be running hotter and hotter if it were clogged. It just went from running cool to running hot one day. But hey what do I know

 

In June I bought a 169,000 mile 2004 4.3 it ran hot. I had to flush/drain the rad. 10 x to get clear water. I had replaced the thermostat water pump and cap and it still ran hot with A/C on. The mud that initially came out of the petcock was incredible. My overflow/expansion tank hose was clogged and sediment was in the bottom. I replaced the radiator and solved the problem of overheating.

 

Thanks for the reply.

Would you mind telling me what steps you did to flush the system? Is it worth it for me to try to flush it first or should I just get a new radiator?

 

I would just replace the radiator. Flushing barely made any difference other than changing the fluid. I just drained from the petcock refilled drove a little drained again. Here is a good source if they deliver near you.http://radiatorwarehousems.com/ P.S. cycle the heater to flush it out also.