It won't stay cool!!!!! :(

[motormayhem]

How much does your trucks temp fluctuate during regular driving and up hills? Mine bounces around in the range of 180-190 but as it has gotten hot out (mid to upper 90s ) it has gotten to 195-200 doing 50Mph up hills. I just replaced the water pump, fan clutch, had the radiator cleaned out by a rad shop and it still seems hot hills to me at least. What do most peoples gems go between? How much does it fluctuate while driving? If I let the truck sit idling it drops to 180 but if it gets up to 200 it takes a while to start dropping. Gonna try some prestone flush to
tomorrow as my coolant is always rusty.

Also is there supposed to be a valve on the heater core hoses? Mine is running hot water through it all the time which seems lime a lot of water bypassing the radiator and possibly contributing to the problem.

 

[cjtroutt]

Flush your system out with vinger 50% with dis warter no coolent at all it will remove lime & rust it realy cleans out system Drain after 2hr running flush & dump antyfreez in, wa lol.
it will run cooler we did this every year on my S60 14L 515HP Detroit Diesel in M915A3.
Hope this help also I done to My M1009 M1028A3 (M35A3 bober Sold).

 

[motormayhem]

Ran prestone flush througt it with no result. Pulled a 2500 lbs trailer today and up hill it went to 210 * I just pulled the t-stat out and with no t stat it ran about 185* after 3/4 mile of 3/4 throttle on a 6% grade. That mean it was the t stat or should it be cooler than that without a stat?

 

[Jones]

Thermostats do two things;
They open and close to let water circulate through or by-pass the radiator.
But they also control flow so that the coolant stays in the radiator long enough to transfer some of it's heat to the core tubes and fins.
If your engine runs cooler then the thermostat may have been stuck closed.

Do you know your temp gauge and sending unit are telling you the truth? Stick a mechanical gauge in there and see what it tells you.

How's your radiator cap? Radiator shops can pressure test them for you.

New thermostats can be bad from the box. The opening temp is marked on the"pill" in the center of the stat, most easliy viewed from the bottom. If you want to make sure it's working right; put it in a pot of water with a candy thermometer and bring the temp up. Watching the thermometer and the thermostat you'll be able to tell if it's opening at the correct temp..

Fan clutches can go out and replacements aren't always trustworthy-- especially the aftermarket ones. Run your engine up to operating temp pop the hood and watch how long the fan continues to spin after you shut off the engine. It should only free-wheel for a little bit. If it seems like too long-- it probably is.

When your cooling suystem is cold do these checks;
How are your hoses? Soft and spongy? Flattened out? Older ones can collapse, or de-laminate on the inside letting a layer of rubber act like a flapper valve.

Trapped air is a problem on some cooling systems and that'll give you fluctuations in your gauge. When an air bubble goes by there's no temperature for the sender to detect. If there's no "bleed screw" then pick the highest point in your system and break loose a hose clamp to make sure you're getting coolant and not air out of there. Tighten everything down when you're sure you've "burped it".

Hope this helps.

 

[motormayhem]

Thermostats do two things;
They open and close to let water circulate through or by-pass the radiator.
But they also control flow so that the coolant stays in the radiator long enough to transfer some of it's heat to the core tubes and fins.
If your engine runs cooler then the thermostat may have been stuck closed.

Do you know your temp gauge and sending unit are telling you the truth? Stick a mechanical gauge in there and see what it tells you.

How's your radiator cap? Radiator shops can pressure test them for you.

New thermostats can be bad from the box. The opening temp is marked on the"pill" in the center of the stat, most easliy viewed from the bottom. If you want to make sure it's working right; put it in a pot of water with a candy thermometer and bring the temp up. Watching the thermometer and the thermostat you'll be able to tell if it's opening at the correct temp..

Fan clutches can go out and replacements aren't always trustworthy-- especially the aftermarket ones. Run your engine up to operating temp pop the hood and watch how long the fan continues to spin after you shut off the engine. It should only free-wheel for a little bit. If it seems like too long-- it probably is.

When your cooling suystem is cold do these checks;
How are your hoses? Soft and spongy? Flattened out? Older ones can collapse, or de-laminate on the inside letting a layer of rubber act like a flapper valve.

Trapped air is a problem on some cooling systems and that'll give you fluctuations in your gauge. When an air bubble goes by there's no temperature for the sender to detect. If there's no "bleed screw" then pick the highest point in your system and break loose a hose clamp to make sure you're getting coolant and not air out of there. Tighten everything down when you're sure you've "burped it".

Hope this helps.

The system was burped. The hoses were good. I have a mechanical temp gauge where the dummy light sensor used to be and I think it is working as the temps only spike on hills and if I accel hard off a light or two, not just showing hot all the time. It isn't getting hot unless I get on the gas. That also leads me to believe the stat was working as if I just sits it cools to like 180 (180*) stat and only heats up when I stary driving it. It has been fine for the past 3 months and after 3 trips on the highway it started running hot. It gets to 190 easily now (used to be the top of its normal range) and I can get it to 200 pretty easy if I try to accel on a hill or floor it off a few lights.

 

[motormayhem]

Ok so I have discovered that the t-stat that I put in from autozone was WAY to small to let it flow and got a stant 190* one and it runs about 190 on level ground and 195 up good size hills. Does that sound about right or should it stay at 190* the entire time. Gonna be pulling a 1500lbs car this weekend for about 10 miles and dont want it getting hot. Also the new fan clutch seems to slip more than the old one. When I shut the truck off it freewheels about 2 revolutions when the truck is at 190*. Is that to much?