running hot?! why?

[parson2008]

my 93 4.0 is running hot it can idle for hours and be fine, but as soon as you take it down the road it begins to heat up to about halfway and slowly keeps climbing, but if i crank the heat it does not get any hotter. the truck has brand new cylinder heads upper and lower intake waterpump and what not... radiator shot? before i rebuilt the top end i had used stop leak but then found out my cylinder heads were cracked... thats when i rebuilt it. so any ideas why its running hot?

 

[zperkins12]

my guess is the thermastat or could be the gauge is reading wrong

 

[parson2008]

thought maybe the thermostat so i changed it and still the same... compression check was done and all cylinders is good.

 

[hondaxr650]

Did you change the radiator? Stop leak can clog one up. It may pass enough water to keep it cool at an idle but not when driving. That's where I'd start.

 

[legoms013]

Stop leak ruinined two radiators of mine.

Clogged the first up real bad. Truck would not run cool.

Then I put another one in, and about a year later some of the stop leak dislodged from the block walls, clogging the radiator up.

Eventually it ran hot enough, and built up enough pressure to rupture that radiator.

My advice. Don't use stop leak, its a bandaid fix with slow repercussions down the road.

Flush your system out to begin with.

It can only be a few things. Clogged radiator, shot fan clutch or stuck thermostat. Or all of the above.

 

[AgPete139]

Make sure you install the thermostat the proper direction. People overlook this in a hurry. Seriously.