Hey Ijust realized this is a perfect place to find the answer to something I've wondered about for quite some time now.
If the temp guage moves but just barely and only gets up way below normal, what other than the guage could be wrong? I pulled the themostat and put in a new one. still barely any movement on the guage. except once when a water line broke and it lost coolant. them it climbed up 3/4 of the way before i shut down the engine. Would putting the thermostat backwards do this?? Seems like that wouldn't make much diference
This is on a 92 ford van with a v8
sorry tojump rigs here but I'll bet someone knows anyway

 

You probably have a ba temp sensor.

 

You may also need to purge the cooling system of any air. If the sensor isn't in contact with fluid, it won't register. I would do this before buying the new sensor sense it costs less.

 

OKAY
I hate to admit this but I never understood howto purge the system of air. My thinking is: if I run the engine awhile with the cap off, any airbubbles will come through and to the top. At least that's all Ive ever done in the past when changing a radiator/ water pumpetc. Straighten me out please
thanks

 

Great question. I've got the same exact issue but I replaced the t-stat and it has improved the temp control. Still get a fair amount of random play with the needle though. Purging would be good to know.

 

I just remembered - one of the most annoying symptoms of my low reading temp. is I can get almost no heat from the heater as if the coolant never heats up. A blocked heater core would cause the engine to run even a bit hotter right?

 

A blocked heater core would do that but if the T-stat is shot and the fan is running continuously the engine could stay cold enough to mess with your heater. Do you get any heat at all from the heater?

 

I get a very small amout of heat from the heater if the weather is warm. If its cold outside then no heat at all.
Like I said..I replaced the termostat...no difference
Noone answered about 'purging the system. Could someone eloborate on the prper procedure

 

Sometimes there is a purge valve in the cooling system and with the engine running and hot you slowly crack open the valve until coolant comes out and then close it back up.
If there is no purge valve then you takethe radiator cap off (when cold) and then run the engine until the t-stat opens and watch the coolant level. Make sure that the heater is set to hot and the HVAC fan on low.
As the coolant level drops you add more coolant until it no longer drops.
Then drive the van for a couple of days and check the coolant level again.
Before you purge the system make sure that your overflow tank is full.
That should do the trick.
If the t-stat was in backwards the engine would overheat because the thing that gets hot and makes it open would be on the wrong side and would not get hot enough to open the t-stat.
Hope this answers you questions.

 

Thanks for addressing those things for me. I have no idea where a purge valve might be on this rig but i'll take look ( suppose that means cracking the hood and getting my hands dirty). thnaks for the walk through on the purge thing -that helps
bc