Engine cooling problem

[Mistral150]

Hi !
First I think I have a bad T-stat because when pulling my camper (over 5000 lbs) on highway, my ScanGauge showed up 182° so look at the needle and it was 2 ticks lower off center.

Today I started the truck to make the temperature rise and see how far it would go. The temp rised up to 199 at max but on my scan tool (with graph) I saw 2 sudden drops in temperature, strange.... Could it be the cooling temperature sensor failing ?

When on idle I went uder the hood to watch the hoses pressure (looked ok) but the fan kicked on at low speed on idle and it was'nt overheating (under 199° and A/C was off and finnaly the air coming out the shroud was cool, no heat, so no reason for the fan to come on ?

Your advise would be great before I start changing things.

Sorry for my bad english, hope you understand !

 

[McGMT]

Hi !
First I think I have a bad T-stat because when pulling my camper (over 5000 lbs) on highway, my ScanGauge showed up 182° so look at the needle and it was 2 ticks lower off center.

Today I started the truck to make the temperature rise and see how far it would go. The temp rised up to 199 at max but on my scan tool (with graph) I saw 2 sudden drops in temperature, strange.... Could it be the cooling temperature sensor failing ?

When on idle I went uder the hood to watch the hoses pressure (looked ok) but the fan kicked on at low speed on idle and it was'nt overheating (under 199° and A/C was off and finnaly the air coming out the shroud was cool, no heat, so no reason for the fan to come on ?

Your advise would be great before I start changing things.

Sorry for my bad english, hope you understand !

I can tell you that the fan does like to engage at idle even when it is not needed. Mine does that alot even when it is cool as a cucumber. Might be time to play it safe and replace the thermostat and sending unit...

 

[Mistral150]

1- So why the fan engage if it does not need to ?

2- Here is the situation update: I plugged a scanner to watch the temp while driving and on the highway with the heater blower at max, the temp was reading Highest 199° and lowest 197° so thats ok for me. Went back home by a secondary road and same mesurement except when stoping to a red light the temp would rise to 201°, that looks fine too so I guess it only appened once. I oppened the coolant cap and there was a little white sludge in the cap (very little) and inside the colar looking like a white jello and last, coolant level seems to be fine and not leaking.

3- while I thing about this... if the fan makes the TICK TICK TICK does it mean I have a bad fan clutch ?

Thank you very much.

 

[Wooluf1952]

The fan will turn as long as the engine is running just from friction.

The ticking may be because you need the PCM up-grade.

 

[McGMT]

The fan will turn as long as the engine is running just from friction.

The ticking may be because you need the PCM up-grade.

I was taking it that he was talking about the very low speed engagement the fan likes to do when you idle them a bit... The infamous "my fan sounded like a jet when I set off, is it going bad?" bit...

And +1 on the PCM update

 

[Mistral150]

My PCM is a PCM FORLESS and the fan was really engaged on idle, it engaged while I was looking at my hoses for pressure. I know when the fan runs free on idle.

I think the TICK TICK TICK was with the old PCM (my mistake)

Thank you.