I have a modified 351W which has a new water pump, aluminum heads, aluminum intake, and a large cam, all of which would have an effect on the engine temp in one way or another. I also replaced the radiator recently and upgraded the alternator to 160 amp. so I could switch to an electric fan, which is said to produce much more CFM of air than the stock fan.

When I start the truck from cold and let it idle, it comes up to temp as I expect it would, but since this is a new motor I don't yet know what the max temp should be. I have a digital water temp gauge (installed a new sensor today thinking the old one was bad, no change) that I have used for years and before I rebuilt the motor, the gauge would read ~220. My new motor should be around 400 hp now but I haven't even got farther than a block or two and the temp spikes to over 260, so I shut it down and wait for the electric fans to cool it off. It seems to cool off fast when I don't have the truck running. The coolant I have is about 75% anti-freeze/25% water.

I am not sure if there is air in the upper radiator hose or not when the motor is on but something tells me that the coolant isn't circulating as it should. So I was going to take out the thermostat and test it. Can I run the truck w/o a thermostat just for the short term to test? Can I run it that way long term? What could I expect to see the temp do if I don't have a thermostat?

Any other thoughts of what I might do to test the system and figure out what is wrong?

Also, one strange thing is if the temp is at 220 and I put it in drive (E40D) with my foot on the brake so I don't go anywhere, the temp immediately starts rising about 2 degrees a second until it gets above 260, then I turn the motor off. But that isn't 100% consistent, if I let the motor cool for 10 min. and then do the same where I put it in drive, the temp starts moving up but then it will go down slightly and then up again where it'll eventually go above 260. This is sort of why I can't figure this out, I don't know what putting the gear into drive has to do with the temp jumping that high. Does the computer put more fuel into the motor when I am in gear even if not moving?

 

What is your timing set at, too gfar advanced can cause over heating. bad T-stat, yes you can run with out it for testing purposed. Electric fans do not move as much air as a mechanical fan with a properly functioning thermostatic clutch. Are the fans wired correctly, i.e. pulling from the front not pushing out the front? Why are you running your anti freeze 75/25, instead of 50/50? No added benefit.

Matt

 

Timing is set at 14* BTDC and that is what Comp Cams told me for the custom grind I have. The timing is now set at what seems to run good, I adjusted it by ear mainly. The fans do push air from the front to the back (firewall). I was running 100% anti-freeze just because that is what I had run for years but today, when it was having this problem, I drained some out and replaced it with water. Didn't seem to make a bit of difference.

Could it be the radiator? This one seems the same size as what came out of the truck: Murray 432183 - Radiator | O'Reilly Auto Parts

 

I would say the only way the radiator is the issue is if a couple of rows are plugged, you can use an IR thermometer to check by compating the temperature on the to row to tthe temp on the bottom row they should be relatively close.I would check to see how much the ignition module is advancing the timing

Matt

 

100%, or even 75% antifreeze is way too much. 50/50 max for cold climates, and 25% would probably do for most people. Ethylene Glycol can not transfer heat as well as straight water can.

220*F at idle is way, way too hot. You should be ~208*F max at idle, probably closer to 190*F. It sounds like your cooling system is barely coping with the engine heat at idle, and just the load from the torque converter is enough to send it over the edge.

Have you tried replacing the thermostat? New ones can be bad. Did you change the water pump? If so, are you sure you got a pump designed for a sepertine belt system? - they spin the opposite way.

 

A block tester will check for combustion gases in the cooling system. Usually when an engine gets hot that fast its a head gasket... you may have damaged one without knowing it. I've seen head gaskets put on backwards or upside down and cause leakage but I'm not sure if thats possible on a 351w

 

Thermostat sticking?

I replaced mine recently with a brand new one and the new thermostat was worse then the original one I was replacing it with... Even though a part is brand new there could be a issue. It happened to me it could happen to you.

 

It is possible, and I think you installed one of your head gaskets backwards, or upside down.
They are marked "FRONT"
Had these symptoms in a buddies Bronco.
Nothing else makes sense.

Go ahead and remove the thermostat.
See what happens.
If there is flow from the bottom of the radiator then you know you have the wrong pump.
Belt routing on my Lima is the same for V or serpentine, but Windsors are different.

 

Will a water pump for a v-belt equipped engine fit on one with a serpentine? The water pump for a serpentine engine is referred to as "reverse-flow". The impeller runs in the opposite direction.

 

50/50 is a better coolant mix.
As soon as you shut off the engine, coolant is no longer circulating.
The radiator may get cool, but the block is hot as ever.

 

Sounds to me like you may have the wrong water pump..

 

Thanks everyone for the questions and suggestions...


Forgot to mention, the older motor had a blower on it, the new motor will after I can put 1000 miles on the new motor. I have a new thermostat installed but my plan is to check that first, since it is pretty easy to get to and check. The water pump that is on there I got from Pep Boys, these motors (351W) and my year only had serpentine belts AFIK so I can just assume they have that in their system to give me the right one. They have in the past.

It is possible to put this head gasket on backwards if you have that type, some are made so it doesn't matter. The ones I have used have all had FRONT stamped on them and I am sure I put them on right.

going to check next

I thought I could remove one of the hoses that come out of the left (while looking from front towards firewall) of the water pump and turn the motor over to see of fluid comes out of those. I think one of the inlets is marked with an arrow for direction.

 

Just turn the engine on with the thermostat open and the cap off.
You will see water flowing across the top of the core if the pump is working correctly.
If the pump is trying to suck water out of the block it should be coming in through the lower hose.

 

Yesterday I had the cap off and saw coolant shooting in from the tube that connects just behind and below the cap. Is that what you mean?

 

The tube behind and below the cap?

Do you mean the overflow tube in the filler neck?
Or one of the radiator tubes inside the radiator?