Engine Lazy T Stat ?

[TOOLOW91]

Driving last night . Do a small pull with the car no big deal car is running 178-180 . It has a 180 stat the air was real Crisp and cool last night . Get off highway cruising through The streets back to my garage . I notice the temp creeping up . Creeps To 200 on the gauge . My Pms is reading 200-206 at the temp sensor . Never over heats . Fan working fine

This morning I get up change the oil to make sure everything was ok . Coolant is clean . Run the car it creeps up again on me and then is fine . I drive the car all day never goes over 190 . Leave work tonight and it does the same it did to me last night after I get off the highway temp wise except I didn't do any pull . Didn't last as long this time and went right back to normal temp .

Am I wrong in saying Maybe the thermostat is closing with how cool engine temp is getting and then it's partial opening until it eventually comes back all the way open ?

It's also drilled at 12 and 6 to allow coolant bypass all the time . This was to help aid in any air pockets and also in a situation if it ever got stuck shut .


Sent from my iPhone using my fingers while my auto correct makes me seem illiterate

 

[Davedacarpainter]

For what my opinion is worth, sounds like a bad thermostat to me.

 

[TOOLOW91]

Still in for any one elses input but i went ahead and ordered a Motorcraft OE 180 stat. I read many similar experiences with peoples stants doing the same thing mine was doing and having the same temp fluctuations.

 

[Noobz347]

It sounds to me like your temp sensor is getting the occasional steam bath.

Purge your cooling system and see if that helps.

Edit: If that doesn't fix it then pressure test the cooling system. Your water separator amounts are still a bit suspect to me.

 

[TOOLOW91]

It sounds to me like your temp sensor is getting the occasional steam bath.

Purge your cooling system and see if that helps.

Edit: If that doesn't fix it then pressure test the cooling system. Your water separator amounts are still a bit suspect to me.

As in between the sensor and gauge ? They are always only a few degrees apart .
I have the mechanical gauge plumbed in the old stock gauge location.

Also ill add i got on the car yesterday during the day and had no issue with it either temp was perfect.

 

[Noobz347]

As in between the sensor and gauge ? They are always only a few degrees apart .
I have the mechanical gauge plumbed in the old stock gauge location.

Also ill add i got on the car yesterday during the day and had no issue with it either temp was perfect.

No, as in an air bubble in the cooling system is finding it's way to your temp sensor. It just so happens that steam is 212*F.

 

[TOOLOW91]

No, as in an air bubble in the cooling system is finding it's way to your temp sensor. It just so happens that steam is 212*F.

I had this thought too . I had it running yesterday for a bit cap off. I topped off the coolant in the rad it didnt take much either. Ill start there and see what happens.

The thermostat is also drilled at 12 and 6 to try to alleviate any type of trapped air pockets.

 

[Noobz347]

Probably fall between the 10 and 15 range.

I've had it happen to me in the 86 before. It was so long ago that I don't recall the events leading up to it but it drove me bonkers for a couple weeks.