overheating/ cooling problem

[quote:3d4d0674ca="hardie775"]this concerns a 91 comanche. inline 6. automatic with about 150, 000 miles. 4.0 liter. same a a cherokee.
yesterday i stalled from overheating and the overflow of the overflow resevoir was overflowing. i topped off the water and shortly their after, 5 minutes maybe, same thing.
the upper rad hose is hot, so i thought not the thermostat, but when i pinch it, i do not feel a surge of pressure upon release. so i replaced the water pump. still the same. and still no surge when i pinch the hose.
the radiator was replaces about 3-4 years ago, so was the water pump. other than the new water pump installed this morning. new rad cap about 2 weeks ago and a new transmission filter about a month ago.
all help appreciated[/quote:3d4d0674ca]

Double check the thermostat could be a bad new Stat again. Never know

Could be air lock in the cooling system, try bleeding it for start see below.

Always bleed air from cooling system after replacing coolant. Set heater for maximum heat. Remove radiator cap. Loosen drain plug and remove drain bolt (if equipped) from engine block. Drain coolant reservoir. Fill coolant reservoir to MAX mark with 50/50 water-coolant mixture. Loosen bleed bolt and fill radiator up to base of filler neck. Close bleed bolt when coolant flows out without bubbles. Tighten bleed bolt. With radiator cap removed, start and operate engine to normal operating temperature. Add coolant if necessary and check for leaks

From: hardie775
To: rasmataz
Posted: Thu Sep 20, 2007 5:47 pm
Subject: overheating/ coolant issue
thanks for the quick responce to my problem. tomarrow i'll bleed the cooling system, but tonight before dark i changed out the thermostat. i still don't feel much of any water pressure in the upper rad hose and the heater while on full is only blowing cold. could the heater core cause my issue? and if so is their a way to bypass it rather than replacing the whole thing, or is my best bet still to blled the cooling system........thanks 4 the assist

Is the thermostat installed properly-sometimes a Stat has to be postion that has jiggle valve-does yours has that. or could be installed upside down.

Heater core will not cause the issue. Bypassing it disconnect the hoses join it together-plug the heater core openings.

Double check radiator for clogging-if not might be a blocked coolant passages in the engine.

Reverse flushing the engine it might break thru.

Good Luck

I rebuild my jeep a500 tranny put a new fron cluth and ckikdown band, pressure sensor and control valve, works a few days good, but yesterday the second gear upshift begining a osilation at low gas, if open the thortle work normal way.