engine temperature droping during starting

[pszczepan]

Hi !

Jeep Cherokee 1989 4.0 l automatic

Recently I noticed something strange.

When the engine is hot the engine temperature is correct (205 F) - quite constance.
When I stop f.e. because lights are red still temperature gauge shows OK, but after that when I accelerating the gauge is droping to 104F and moment later it is once again 205 F.

Do you have any idea what is the reason of that?


Hmm

Pawel

 

[TiRod]

Possibly, the thermostat is wide open at the light, on acceleration, the radiator gets extra cooling from movement, and the engine sucks in a slug of colder water. Temp goes down until the extra engine heat warms it back up.

I'd say your radiator is working ok.

 

[Slo-Sho]

Check your coolant level.

 

[xj88superjeep]

When you accelerate, the clutch fan speeds up, and sucks ALOT of air through the rad, and the water pump is gonna suck all that cool water into the block. That's my take, unless it is overheating, then cooling, which would be low coolant level, or air in the system. How's the plastic overflow bottle? any cracks or leaky cap?

 

[pszczepan]

When the engine is not overheat the coolant level looks OK, but I also noticed that during the hot day when the tempeerature is going really high the coolant level is going up to the top of overflow bottle and I saw there small crack. High coolant pressure going throw it.

Do you think that my problem lies in cracked overflow bottle?

Thanks for reply
Pawel

 

[old_man]

My bet is a corroded connector on the back of the gauge cluster.

 

[xj88superjeep]

When the engine is not overheat the coolant level looks OK, but I also noticed that during the hot day when the tempeerature is going really high the coolant level is going up to the top of overflow bottle and I saw there small crack. High coolant pressure going throw it.

Do you think that my problem lies in cracked overflow bottle?

Thanks for reply
Pawel

That pressure bottle is under a vacuum when the engine is cool, and under pressure when it's hot. If you have a crack in the coolant bottle, you will lose your fluid when it overheats instead of it being forced back down into the radiator. Then when it cools after you shut it down, the vacuum will suck air because the coolant blew out the crack when it was under pressure causing constant air bubbles in your cooling system even if you add more fluid before every trip... You may have an additional problem causing the hot temps that put extra pressure on the bottle, but you won't know until you replace the bottle (mandatory) and see if she still acts up.