Thermostat Gauge Going Crazy

[JayTye4k]

95 XLT

Hello all,

For the past week I've noticed that my temperature gauge on the dash bounces around the "C". It never goes up to Hot, but it constantly bounces around the bottom of the gauge, never staying in one spot. I recently changed the sensor, but I'm thinking this may be the thermostat this time. Any thoughts here? How serious is this? Is it cheaper for me to do it myself or take it to a shop? Is it a hard project to complete by yourself?


Thanks in advance for any help provided!


Jay

 

[spta97]

I've got the 5.0 V8 so I'm not sure if this will apply but it was rather easy. The thermostat was located on the engine right within site. The hardest part was getting off the two bottom bolts - a swivle socket would have helped.

If you haven't done it within the past year, I would sugguest to flush the whole system. Drain from the radiator (into an approved container for disposal) and flush it out with a hose. Then do the same for the engine where you took the thermostat out (you'll need to disconnect the hoses for this too). Once the system is running clear water throw in a 50/50 mix of antifreeze and distilled water.

Some people here actually get a couple of thermostats and boil them in water to make sure they open when they are supposed to. I was lazy and just threw it in - temp gauge is just below the picture of the thermometer on the gauge and doesn't move once warmed up - regarless of outside temp.

****Anti-freeze has a sweet taste to it so animals and kids might drink it if left in a puddle. This will prove fatal so make sure you rinse off any anti-freeze that you could not capture in the container****

 

[EBInterceptor]

The themostat is a relatively easy job to do. The OHV, SOHC, and V8 have different thermostat locations, but the idea is still the same. Pick on up from your parts store, long with a gasket. There have been a few posts on here at least about how to do the change, but if you don't have a Hayne's of Chiltons manual, you might as well pick on of those up too. Flushing the system is a little more time consuming than just changing the thermostat. Either way, you're going to need to drain some of the fluid out when you do the thermostat, but can reuse it if it's good condition. If you don't want to go through the trouble, you might just want to bring it into a shop, but they may charge you enough that it's just better off doing it yourself.

 

[ohe_boy]

I have a temperature needle that also moves around the lower part of the gauge, anywhere from the C to the O in NORMAL. But here's the thing, I don't have a thermostat installed. Whats causing the needle to move so much?


BTW - A thermostat is not practical where I live but will it change the performance of the engine if it's not installed?

 

[mosinman]

Thermostat

ohe boy. You have some incorrect info. A thermostat is ALWAYS necessary - period. Engines are designed to run at a certain temperature, and this is what the thermostat regulates. The climate where you live has absolutely NOTHING to do with it. I don't know how to state this more plainly. Poor engine performance, poor gas mileage, and reduced reliabilty are just a few of the hazards of always running your engine too cold.

If your temp guage is always near the bottom,it is because your thermostat is probably stuck in the open position (or gone in oheboys case). It is also possible that the guage or sensor is broken - although the thermostat is the likely culprit. Wildy fluctuating readings can mean air in your cooling system, or a bad guage or sensor.

 

[TPLYNCH]

Fluctuation can also be caused by a weakened radiator cap spring. The pressure built up in the system will release thru the cap if the spring has weakened with age.

 

[ohe_boy]

mosinman - I've always wondered about that. You see, I had some overheating problems sometime last year and heard that in Hawaii, it's not REALLY necessary to have a thermostat. BTW the thermostat was bad which caused the overheating. Well I replaced it with a 180 degree thermostat. 6 mos down the road that one went bad. WTF?? ANyway, to make a long story short, I just removed that one and never put another one in. But I always wondered if it needs one to operate efficiently. Since I do need one, what is this "certain temperature" it needs to operate at? Just so that I can get the right thermostat.

Also, what is the average lifetime of a thermostat?

 

[TPLYNCH]

I think stock T-stats are 195 degree. I just replaced mine for a second time @ 130K.

 

[Brain]

Stock is 198, although 195 will do. I think anybody with the '91-'92 that have the original heads might do well by going down to the 180 model (because of the historical cracking between the valves). Going down in temp will increase the fuel consumption slightly. If your t-stat only lasted 6 months, you either need to flush and refill with new antifreeze (corrosion protection descreases with age), or quit buying the $2 t-stats and pony up the whole $6 for a better brand ; ) (just kidding)

Prestone makes a flush-n-fill kit that only costs about $4, and it gives you a good way of fully flushing the whole cooling system (not just the radiator).

 

[dreamr]

I was just going to post a question that is very likely related to this very thread. Since it is only a couple days old, hope you don't mind if I revive it.

Yesterday I went and played a bit. Some pretty rough roads due to recent mudslide and washouts.

Toward the end of the day I noticed that my temp gauge that is normally hovering right in the middle is down to about 25% of the gauge, med-low shall we say. It has not risen much past there at all today. Though it is fluctuating mildy which it has never really done before once warmed up.

My question is did I damage something, get to much water or mud somewhere, or did my T-stat decide to go bye bye and it is just a coincidence?

 

[TPLYNCH]

How many miles you have on it? They only seem to last ~ 60K. I've just replace the T-stat for the second time on mine @ 130K. Chances are it decided to pick now to just crap out on you.

 

[dreamr]

a touch over 90,000. I was pretty sure that's what happened, and have since confirmed such by it's actions over the week. Ya never know though when you are bouncing around and what not and suddenly a gauge starts reading funny.

Purchased a new T-Stat on Sunday. Hopefully I won't freeze too bad till the weekend as the heater won't get hot enough for my taste. I suppose at least it still runs slightly warm, and I should have time tio install this weekend.

Thanks for the response!