My 95 is running hot. Quircky hot. Gauge sits at 200 most of the time. Then suddenly jumps to 280. Sits there a minute or two, then instantly jumps back. Other times it will creep slowly up into the red zone, then fade slowly back down to 200. This has been going on since last summer but rarely in the winter with outside temps cold. Now it'* becoming a big problem. Car has never overheated, boiled over.

Last fall I just thought the gauge was acting up, the way it was going crazy, but I don't think so anymore.

Here'* the dirt.
> I'm original owner, flushed and filled the car many, many times over the years.
> I change the water pump two years ago. Big PITA. 10 hours in freezing cold weather.
> Radiator is original. Never had issues. Everything flushes clean, fins, tank etc.
> I decided to change thermostat, rad. cap, and CTSs, even though they were not old. They had no effect.
> Cooling fans don't come on properly, I have manual override switch but it does not change the fluctuating temp one bit. Sometimes engine gets hotter when I turn the fans on.
> No leaks, no coolant loss, no weep hole drip, and water pump pulley is tight & smooth spinning.
> Upper rad. hose gets hot, but not too hot. Lower rad. hose stays cool most of the time... every once in a while it gets really warm. Radiator stays cool, never getting really hot to the touch.

I think I have a flow problem. Comments appreciated here.
I don't have a scanner, but I don't really think the CTS and PCM numbers are all that relevant, considering the lower radiator hose is often cool to the touch.

The questions.
> I can check the flow through the radiator without much hassle, but the only other component to screw up the flow is the water pump. Right? Is there a way
to check its flow production without removing it? I hate that darn thing.. PITA.
I know the impellers can come loose etc. but I want to be sure before I go through that again. :(
> Would a head gasket issue stop all coolant flow? I do have a little bit of oil appearing
around the head gaskets, but not enough to drip or even smell.
> Is there something else I'm overlooking?

Kind of long explanation. I've done searches, most point to WP or radiator if it'* a flow problem.

This may be way too simple to fix your problem, but are you sure you bled it properly? My car did the exact same thing once when I refilled the coolant and didn't follow the proper bleed procedure.
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When I did the recent thermostat and CTS change I was really careful about getting out any air. A lot more careful than other times. I've never had issues in the past. The bleed screw on top of the thermo housing has always worked well for me.
Are air pockets something that an old car can develop when it never used to?

Are you certain you don't have a ground problem that'* affecting the gauge? Before my 93 got wiped out I was fighting similar problems. I never found the problem before the car got crunched, but the temp gauge was doing crazy stuff and the car was not overheating. Can you install an aftermarket gauge or something like that to verify your temp is really staying constant? If you can isolate the fault to the gauge, at least you won't have to worry about the WP volume or anything else in the cooling system...you'll just need to find the source of your electrical problem. I suspect with my car it was probably hidden corrosion in the battery cables.

The lower radiator hose should be really hot to the touch after an hour on the road, should it not? Or is the radiator in the SSEi'* that good.

Motorhead, I did notice one time the gauge did not start all the way to the left, ( I think it'* about 100 degree F) but it started at about 150 degrees when the engine was cold after initial startup. It only did that once, however.
If the ground is going bad to the gauge, would it ever read below normal operating temp as well as above? Because now it only reads normal warmup, then normal operation, then sometimes too hot, but never too cool.

Do after market gauges just tap into the CTS circuit or do you intall another sensor somewhere?

I may take it to a shop to scan the PCM temp if you really think the car is not actually hot, but knowing my luck the gauge will read perfect that day, and I will waste $50.

How about removing the thermostat so you can see if the coolant is constantly circulating?
Did the thermostat get installed correctly?

Changing the thermostat last week had no effect. I assume both the old (not really old) and new one are working / installed correctly. I'm pretty good at simple repairs.

How could I see the circulation of the antifreeze. Maybe some clear hosing to replace the upper radiator hose. I couldn't allow it to get too hot, but then again it may not get hot if it'* flowing properly without a thermostat.

I think I read that waterpump impellers can come loose when the pump gets hot. That'* what I'm really trying to test, I think. Impossible, I know.

Maybe the air pocket thing warrants some more investigation also.

Without a thermostat the coolant should always be moving. Just leave the radiator cap off and you'll see the coolant moving if the pump is working.

Sorry, I thought of that after posting. I will work on the air pocket possiblity first, because removing the thermo will put MORE air in the system when I replace it. But thanks for the insight, it will be my next step, if the air idea can't be resolved.

Is there any other tricks to removing air other than the bleed screw?

You can grab the upper hose and give it some gas. You should feel a slight decrease in pressure if the pumps working wright. Bleed it per the Technifo article.
A lean 02 and an EGR valve thats not working could also cause cylinder temps to spike up rapidly.