Temp. Question?

[mercury]

Could someone please help me. I just bought a 91 X. I noticed when I drive it the Temp. gauge cycles between the "N" in "NORMAL" and the "M" pretty regularly.
It does not seem to matter weather I'm in the city or on the highway. I have already changed the thermastat and flushed the the system. Can anyone please tell me if this is normal. Thanks.....

 

[88vert]

Did you test the new one before you put it in?

 

[mercury]

yes I did.

 

[88vert]

I had a bronco 2 that used to do that all the time it ended up having air lock in the system

 

[PekingMan]

I have the same problem and I was going to do some things to fix it as well, but what and where is the "air lock" that 88vert talks about?

 

[88vert]

It is when you get air in the cooling system and it messes with the thermostat

 

[racerat94]

Me three

I have the same problem in my '92. I replaced the stat and the same thing happens in a little warmer range. I posted this question before (you can find it by doing a search for "racerat94") and a guy said he put a temperture gauge on the "pipe", I guess he meant the upper hose and it stayed at 195.

Temperture fluctuation is a very bad thing for an engine. It stresses the metals especially cylinder heads (an aluminum head would probably have warped and melted the head gasket by now).
I also worry that this will cause inconsistent oil temperture which is critical to a long lasting healthy engine.

I've never heard of "air lock", sounds odd.

My next step is to somehow check or just replace the temperture guage sensor in the block. I'll keep you informed...

 

[88vert]

Have you tried running the system with your heat on full with the radiator cap off then topping off that way if you have air in it that is the way to get it out

 

[racerat94]

No, come to think of it forgot about the heater core when I refilled. I'll try that when I get home if it aint raining.
Thanx man.

 

[Ross-N-Chicago]

I had the same thing happening to me on my 91. Replaced the stat 2x with Motorcraft, still cycled. However, when I put a new water pump on it totally solved the problem. Now every once in awhile it will move off the N to the O or R and then settle back down for a long time on N. Hope this helps.

 

[MyExp]

I had the exact same problem. I replaced the old T-stat with a Jet T-stat from performance products. Problem solved.

Btw, the old t-stat was sticking.

Brian