If the outside temp is in the 60-70 degree range may ECT will be 190 and my EOT will be 200.

A 10 degree differential at 65 MPH fully warmed up, unloaded on flat ground.

If the outside temp is 90 degrees or higher my ECT will be 205 and my EOT will be 215 under the same driving conditions.

Same 10 degree differential but 15 degrees higher for both readings in hot weather.

Is it normal for this much of an increase based on outside temperatures or could this indicate a radiator or water pump issue?

 

doesn't sound right.

The motor and water pump are controlled by the thermostat. It shouldn't matter the outside temperature. At 190*, the t-stat should open, if its 65* outside, then it would just take a little longer to get to 190*.

Is the fan working correctly?

 

Hi WatsonR,

Not sure what you are asking.

My ECT temp always reach 190 fairly quickly but I noticed when it is hot outside the my temps on both ECT and EOT will be 15 degrees higher than at cooler outside temps.

My fan RPM vary according to the ScangaugeII and the fan will kick in full bore when the ECT gets to around 215 or so if pulling.

The fan will occasionally roar when leaving a stoplight in hot weather for a few seconds too, then drop back to normal levels so I think the fan is working properly.

 

what I'm saying is that it doesn't matter about outside temperature.

100*outside temps get you 190* coolant and 200* oil.
65* outside temps should get you 190* coolant and 200* oil.

Your thermostat may be going.

 

Hi WatsonR,

Now I get what you are saying.

I replaced my thermostat about 3 months ago as preventative maintenance and the readings are the same with the new one as the old one.

On both thermostats the same scenario occurred in regards to ambient temperatures.

Both thermostats were OEM Ford replacements.

 

why I asked if the fan was working correctly.

Just doesn't add up, warmer days make the truck hotter.

It's 90* here today, my truck hits 200* because of the thermostat I have installed, it hits 200* every day even when it was 50* outside. Yesterday 89* outside, 200* on the way home for coolant.

 

Towing will increase the temps of the truck, the overall temps are a little higher when working it. When I tow, I see 207* for coolant instead of the normal 200* coolant unloaded. For me, this is normal and may be what your asking?

This number could increase if your hauling a bigger load.... then yes, its normal. The motor generates so much heat and the coolant is only so efficient.

 

Do you think that a radiator blockage or failing water pump could cause this scenario?

It has been this way for quite a while and it never gets any worse so I have always left it alone but I have been curious as to whether this is normal for a while.

Truck runs perfectly otherwise.

 

The numbers I mentioned were when not towing, driving 65 on flat stretch after truck is fully warmed up.

When towing the same scenario will occur but the temps will rise a bit.

Differential is never greater than 10 degrees or so but operating temps will always be higher (unloaded or towing) if the outside temp is over 90 degrees or so.

 

if radiator is blocked, then yes, efficiency would be down... could be a dirty radiator from bugs or as you mention, pump could be going out. How does it do towing?

You could wash the bugs out from the inside>outside (reverse flow) and see what happens.

 

The radiator doesn't look like it is clogged but I'm sure the inside/outside flush can't hurt!

I believe the water pump is the original.

When towing the temps will rise by an additional 10-12 degrees but the delta will remain at around a ten degree differential.

 

Been thinking since I left work. Ambient temp increase would effect the radiators ability to disperse temerature to the atmosphere. Go after the radiator first by cleaning the bugs and then see what happens. New Mishimoto is around $300, all aluminum and has good rewiews.

It's got 220k miles and bugs on it, not bad.

 

Thanks for your input Randy.

I will give the radiator a good cleaning this weekend and post any changes or observations here.

If that doesn't help I guess I will go for a new water pump to eliminate that as a factor (at over 220K miles it can't hurt to upgrade the pump).

Probably go with the BPD machined one so I won't have to worry about it in the future.