My truck has been running a little warm over the last few months, but only while driving and it seems to happen during both highway and stop-and-go situations. If I start it up and just let it idle it won't go over 195 (using a Autometer coolant temperature gauge), but while driving around it will creep up to ~205-210 depending on the ambient temperature. My old radiator had a lot of buildup (I would be surprised if the PO ever flushed it) so I replaced it with a two-core unit recently and I hoped that would help. I checked the water pump when I replaced the radiator and the fins all looked good and it spun freely. Unfortunately, it didn't appear to make much/any difference. The only thing that I can think that might be causing this is that I increased the spark plug gap to 0.055" and advanced the timing to 12 deg. Its also got an MSD coil and 8.5mm wires on Motorcraft copper core plugs. Would that lead to the engine running warmer? Any thoughts?

Thanks!

 

The old Hanes manual I keep in the bathroom says the stock wax pellet t-stat begins opening at 170° and is fully open at 210°. Did you replace it with a cooler t-stat when you did your other rad work?

 

There's nothing wrong with those temperatures. The warmer it runs, the better & more-efficiently it runs. I'd check that gauge against an IR thermometer.Are you saying you pulled the WP out of the engine block to inspect the impeller? Or are you talking about the fins on the fan clutch?Not necessarily, but I don't think you're doing the engine any good changing those settings. And MSD coils have a reputation for catching fire, so keep an eye on it.

BTW
Your signature would be more useful if you decoded those VC label codes. But you already have the transmission listed, so there's no need to repeat it.

 

Steve83,

that is untrue. The warmer an runs is not better nor more efficient. The hotter the coolant temp the more fuel the engine needs to make the same power. On the fuel mapping it starts adding fuel to the multiplier over 140 degrees. If you take 2 identical engines and run one with a 160 degree thermostat and another with a 195. The engine with the 195 stat will require more fuel at any given rpm across the board.

The engine with the higher thermostat will have cleaner tailpipe emissions with all sensors in the correct range but ONLY do to the added heat of the cylinder temps and the catalyst action. An engine with a 160 degree thermostat can actually be tuned to have better tailpipe emissions than the engine with a 195 stat and in most times the engine with a 160 stat can have the fuel trims set to cut 5%-10% fuel..... done it many times myself

Engineers will tell you the only reason for high coolant temps is for super heating the convertor quickly for EPA emissions.... most of their toys and other stuff use 160 stats

 

You should study physics, thermodynamics, & mechanical engineering. The higher the peak temperature of an Otto-cycle engine, the more-efficient it is. It has nothing to do with emissions - it's complex (but still basic) physics.

 

I've studied all that and have been building engines since the 80s... dyno results say different....

 

Then you should be familiar with the good old P-V diagram:



And you should know that any dyno that disagrees with it is defective. The larger the area inside the power loop (minus the area of the pump loop), the more power the cycle produces. And higher temperature means higher pressure. Lower temperature means more HC being wasted out the tailpipe.

 

I'd say the fan clutch isn't working 100%. Back before I had an e fan I replaced the clutch a few times. The aftermarket units either locked to early or didn't lock at all. Working properly our heavy duty clutch should run the fan at 60% of rpm and go up to 90% of rpm when locked. The clutch fan should always be pulling a lot of air across the radiator. The timing advance could also be playing a part.

 

I replaced the thermostat a few months ago. The PO had a 180 degree unit in there and I replaced it with a 195 degree to return it to the factory spec. The coolant temperature holds very nicely at 195 degrees if I just fire it up and let it idle.

 

Should I check the temp with an IR unit on the radiator or somewhere else?

I pulled the water pump out and checked the fins. I removed the fan/fan clutch and replaced with e-fans, which come on at 195 degrees. I was having the same problem with the old fan in there and was hoping that it would have been resolved after replacing the radiator and fan.

So, should I not be concerned with coolant temperatures in that range? If not, at what coolant temperature should I start getting concerned?