1995 Chevy 454 P30 overheating

Never chase a problem until you double check the reading with a different gauge. Gauges go bad too.

The water pump is a real pain to replace with the radiator in the rig.
I would suggest taking the AC condensor bolts loose,(don't disconnect coolant lines) pull the radiator, replace the water pump and all the belts. Belts are very easy especially the second power steering/brake pump one. It will take a little longer but you will be more confinent that the problem has been resolved. I replace my radiator a few years back with on from O'reilly's. It helped the cooling better then when it was new. The core was much thicker. It used the same bolt holes so it was a direct replacement.
Radiator

Thanks guys you all the thoughts. This is a MH we bought strictly to rent it out, so I need to get this right. It comes back Sunday from a 4 day rental and I am going to take the time to get it right before it goes out again! I will start with a complete flush and pressure test, then to the thermostat and finally to the water pump, it is debris free even behind the condenser. So I should come to a conclusion soon. I will post back as to my outcome and/or progress on the way.
Again thanks so much for the input, it is really appreciated!

My 92 was overheating and I replaced the thermostat and that didn't fix it. I thought it might be plugged also, but it turns out that there was too much debris between the condenser and the radiator. Took the radiator out and had it flushed since I was that far into it and the shop said he got a little gunk out of it, but that it wasn't that bad. He also pressurized it to some crazy pressure just to see if it was still solid on the inside. It held and now I'm back in business. No more overheating. The thermostat is about a 15 minute job on my 454. Easy to get to, easy to replace. I'd try that first since it's cheap. Let us know what you find out. BTW, those aren't cheap radiators and having one replaced was going to cost me close to $1500. That's why I tore into it myself.

Tom

Radiator, Radiator, Radiator, At that age, Radiator. Once you get past the denile it's time for a recore.

I would not think the waterpump would be the issue as the first thing to usually give on a waterpump would be the seals or bearings and it would leak. You say you don't believe it is the thermostat since it works at speed but maybe it only opens up when the engine is hitting a much higher temp only achieved under load and not reached when idling. You should be able to see when the thermostat opens while idling by watching the temperature gauge. When it opens (about 195 degrees I beleive) the gauge shuld lower a few degrees. If that is not happening the thermostat is not working or the coolant is being prevented from reaching the thermostat someway. I would have the radiator professionally flushed and replace the thermostat. Also check your primary cooling hoses from the radiator and make sure they are not collapsing.

vegasfoodguy wrote:
Fan clutch.

I replaced the fan clutch with a direct drive spacer and a six-bladed fan, no change. The thermostat seems to be working as it runs about 200* while cruising at 65 mph. That's why I'm thinking water pump. Is there any way to test the pump?

Vegasfoodguy has it right. If it overheats at idle, there isn't enough air moving through the radiator. Once you get above 30mph, you have enough ram air effect to force air through the rad without a fan. Get a working fan clutch and also check for obstructions in the radiator core i.e. bugs, dirt, leaves, etc. and give it a good cleaning as necessary.

Fan clutch.

I just got done replacing all of my cooling components on my '94 georgie boy pursuit. This was a water pump, all coolant and heater hoses/clamps, coolant, radiator flush, thermostat, fan clutch and all belts also. This thing runs like a dream and has never overheated. I wouldn't say I run it hard, but I don't drive like grandpa either. If you have a hanging or bad thermostat, it will overheat. Sometimes it will open, other times it won't. And when it hangs open the water all gets to the same temperature, never getting a fair shot at the radiator to get cooled off. It was a pretty involved job with all the brackets and stuff having to go on and off in the correct order, only fits one way. Your rib cage and stomach will be sore for a few days after the job, from laying on your stomach and chest for hours on end cussing & sweating...That said, i'm glad it's all done.