Engine cooling problem

Mistral150

Original poster
Member
Dec 7, 2011
24
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

Member
Jun 17, 2012
621
Mistral150 said:
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

Original poster
Member
Dec 7, 2011
24
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.:thumbsup:
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
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

Member
Jun 17, 2012
621
Wooluf1952 said:
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

Original poster
Member
Dec 7, 2011
24
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.
 

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