Inliners International Forums General Discussion Engines engine temp

i have a 250-6 cyl in my 40 panel truck.it is a used motor, not much knowledge on the history of the motor.it runs good and i have the original radiator i ran it at first without the thermostat and it was fine it would just run at 190. i thought i would put in a thermostat now that i have a heater but it instantly started running upwards of 220-230 and even short 10 minute drives causes it to lose a bit of water after i shut it off . this leads to needing to add water after every 2 0r 3 times that i drive it . i went with a 190 thermo thinking it stays at 190 without it ., why not . should i go back to no thermostat or use a lower temp? we hardly need a thermostat here in california.who can help me.

It is not unusual to get a thermostat that is defective from new,I would try another thermostat and see what happens first,then if it works properly, return the other one,if not then start checking other areas.....jimm

Dr.Tile,When you say you're using the original radiator are you referring to the 1940 one or the one that came with the 250? If it's the 1940
radiator maybe it's cooling capacity isn't sufficient with the 190 temp thermostat after it opens. Also, how about the cooling fan? Is there space for enough air flow between the engine and radiator? If it ran well without a thermostat why bother now unless you'll need quicker heat from your newly installed heater in the winter.
The worse scenario is that the block is partially plugged from rust and the thermostat
worsens the problem.

a good way to clean out the block and heater if they're plugged or dirty is to stick a hose on one end and have the other hose pointing towards the ground...i had heating problems before..i used some radiator drain cleaner which sorta helped but not for long...so then i just took a hose to it...u shoulda seen the crap that blew outta there.

To test the thermostat, just drop it in some water on the kitchen stove and see at what point it opens up.

Generally speaking, you're not supposed to run without a thermostat or restricter plate. The reason being that if the water is allowed to go through the radiator too fast, the radiator won't have time to pull the heat out of the coolant, and you will overheat, or at least run hotter. The rate of flow is often overlooked. A huge radiator may not help, if the flow rate is all wrong, for example. If you are running fine without a thermostat, then I would suspect that possibly there is allready a restriction of some kind at work?? and that adding another one in the form of the therm. is putting it over the top. Of course, I could be totally of base too...

Are the belt pulleys the right size?
How close is the fan to the radiator?
Does the lower radiator hose have a spring in it to prevent it from colapsing?
What shape is the radiator in?
Check the thermostat. Make sure it's installed the correct way. Add a small hole in the flange to allow air to escape for when you are filling it up.

You may want to add an overflow tank to the system. I have used those stainless ones from the magazines before, but have found them to be too small. If you have the room, a large factory plastic one mounted out of sight under the fender would be cheaper/better, in my opinion. Make sure you are using the right kind of radiator cap also.

thanks for all the great input . i think you are all right in some ways. the radiator hasn't been redone . it is the original for the truck . probably is some restriction there,and maybe the motor ,too . the hoses are new but this radiator has a one and one quarter inch upper inlet. i won't be driving it much and it seems to run just fine since i have now gone back to no thermostat. in the future will do the radiator when i use it for a daily driver . overflow tank is in the future ,too , though it seems that it only goes into the tank never back in the motor...you know what i mean!

Dr Tile, what about the condition of the radiator cap. I think the stock one was only about 6psi--- why not go up to 12-14 psi cap ---that would probably stop the fluid dumping. Also adding the close cooling resvoir asap wouldn't hurt. If coolant is 190 when the motor is running when you shut the motor down the temp will go temporarly maybe as much as 15 degrees, so the added pressure will help raise the boiling point. 50/50 antifreeze is a must here in Texas year round because of the added boil point increase. Just some thoughts ---Paul

There are 2 kinds of radiator caps. Ones that allow coolant to be pulled back into the system, and ones that don't.
Like Paul says, a higher cap pressure would slow down the overflowing. A word of caution, adding more pressure to these older radiators and heater cores may result in a trip to the radiator shop because of leaks. At any rate, 7 lbs. would be the minimum that I would run, more if it can handle it.

On my '46 GMC pickup w/ 302, I was told by the radiator shop not to go over 6 or 7 PSI on the older radiators. Getting your radiator overhauled is cheap insurance and saves a lot of fooling around later.

When you find the thermostat you like, I'd also rig up an overflow bottle to keep from having to top off all the time. Also I wouldn't run 100% coolant, just minimum amount for corrosion protection, water acutally transfers heat/better than coolant.

The idea that water can flow too fast through a radiator and not cool is false. There is no thermodynamic basis. I've tried this on my 302 and it runs COLD, it overcools. The original poster said that it ran cooler without the thermostat (190) compared to the thermostat (220). I'm not trying to be critical, but where does this notion come from?

Jason, I agree with you EXCEPT Dr.Tile is using his original 1940 radiator which could be smaller capacity and less cooling rows to efficiently cool the 250 he is using.The removal of the thermostat allows the coolant to circulate in the radiator and airstream quickly whereas a thermostat may allow the temp to raise sufficiently enough that cooling becomes a problem.