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Old 12-03-2007, 10:57 AM   #1
madmatt2024
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Temp Gauge Acting Weird

My friends mom has a 95 Windstar 3.8L. She bought the van with the engine freshly rebuilt with the revised head gaskets about 6 years ago It has been parked for about 2 years because of an "overheating" issue. It has been moved several times throughout the 2 years so it does still run and drive. The drivers side rad fan didn't work so I replaced the fan motor with one from the junkyard and now that works. The dropping resistor was also bad but I repaired it so now the fans come on. I also replaced the thermostat. However it still has the same problem. The temp gauge will rise to the middle of normal, pause, then keep rising to H or around there, the radiator fans come on, it will stay there until the fans turn off. The instant the fans turn off it plunges to the middle of normal in 1 sec. It sometimes will also rise about 1/4" in under a sec when its on its way up to H. It will do this at Idle but the temp comes up faster if I rev it. The heater blows hot through out all of this as well. It did this before and after I replaced the t-stat. The temp gauge will also start going up if there is a current draw. For instance, if I push the power window button it will move up a small amount only to go back down when I release the button, the heater blower will do the same thing as will the headlights and pushing on the brake. Given all of this I don't beleave its actually overheating, I think there is a problem with the gauge. The question is what? I am planing on replacing the temp sender for the gauge but what else could be wrong? Should I be on my way to the junkyard to get a new cluster or is there some ground that could is bad?
The overheating/temp gauge issue needs to be fixed before we move on to other issues, like the brake lines and getting a new battery. There is no since doing them If the motor is going to be a problem.
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Old 12-03-2007, 06:08 PM   #2
wiswind
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Re: Temp Gauge Acting Weird

Air in the cooling system will cause the temperature to fluctuate....and even overheat.
The air could be in there from when the head gasket work was done....
If there is a leak in the cooling system.....it will enable air to enter....and cause temperature issues.
There ARE other places for air to enter......lower intake manifold gaskets, loose hose clamp, etc.

By the way, were NEW lower intake manifold gaskets installed?
They are NOT re-usable.....so they MUST be replaced during the head gasket job....as you have to remove the lower intake manifold to remove the heads.

It sounds like you may have a electrical issue......which could be the battery and/or alternator.....as well as dirty/loose connections.
I would start at the battery, if unsure....replace it.
Remove and clean the inside of the battery terminal cables as well as the surfaces of the battery terminals....they can build up oxidation.....looking good, but not making a good connection.
Sitting around is a prime situation for bad electrical connections as well as draining the battery.

You have 2 temperature sensors, 1 for the temperature gauge, and 1 for the PCM.
I show them in one of my photos, in the pictures that the link in my signature takes you to.
They sit right next to each other.....above the thermostat that you changed.
I do not think that they are interchangable....as they are listed as 2 separate, and different parts in the part ordering information that I have seen.
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Old 12-03-2007, 08:40 PM   #3
madmatt2024
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Re: Temp Gauge Acting Weird

Other than the head gaskets I have no idea what was done when the engine was rebuilt. I do know that the work was done by a well known local shop. Besides his mechanic business the owner goes to the auction and buys cars to sell. He bought it, rebuilt the engine, and put it for sale. I do know he has a full machine shop and that they do engine rebuilds. It never had an overheating problem until two years ago when it was parked. I need to ask her how the problem started but I think it might have been a thing that just started happening. The weird way the gauge is acting is leading me an electrical problem. The battery was replaced a few months before the overheating problem started. All that sitting ruined the battery so I got a temporary replacement from work, a used CAT battery. Needless to say I had no problems starting it. I know about the two temp sensors, I unplugged the one for the gauge and it dropped, I plugged it back in and it went back up. The gauge seems to want to stay around the middle of normal but then it keeps climbing and falling. Despite the temp gauge reading beyond normal the system never overflowed or started to steam while I was testing it. When I replaced the t-stat I blew into the top rad hose and could easily blow through to the other side so I know thats not clogged.

What is the normal operating temp range on the Windstar? I might have access to an IR thermometer to get a true reading but I will probably have to wait until next month because her money it tight this month and I had to return the battery.
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Old 12-03-2007, 09:45 PM   #4
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Re: Temp Gauge Acting Weird

Since it has never steamed I think you are on the right track looking for an electrical problem. I would be looking at engine to frame grounds, If I remember correctly there is a jumper from the negitive battery cable to the radiator support. Make sure it is there and the connection to the radiator support is clean and tight.

Grounding issues between the engine (where the alternator is grounded) and the frame (where all the accessorys are grounded) will cause the gauges to vary with the voltage diffrence. You may even want to put an extra jumper between the engine and frame to see if it fixes it.
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Old 12-03-2007, 10:12 PM   #5
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Re: Temp Gauge Acting Weird

When I replaced the t-stat in my 2000 Winnie, the original had a small
bleeder hole located in the top with a brass rivet to act as a check valve
I assume. The replacement T-stat didn't have this bleeder hole so I drilled
one with the smallest drill bit I had. This would prevent any air from being
trapped at the t-stat. You mentioned that when wire was pulled from sender
that gauge would drop. Try grounding the sending wire, gauge should peg the other way, if it doesn't stay pegged the guage may be at fault. If you can obtain an IR thermometer you can also get
some idea of radiator efficiency by comparing temp readings on the inlet at outlet.
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Old 12-04-2007, 07:34 PM   #6
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Re: Temp Gauge Acting Weird

When I have my scangauge connected, the engine temperature stays at a steady 192-193 degrees while cruising down the highway.
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2003 Toyota Sienna pictures (not much there yet)
http://www.flickr.com/photos/4157486...781661/detail/
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Old 12-04-2007, 09:45 PM   #7
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Re: Temp Gauge Acting Weird

All indications appear that there is a problem with the instrument cluster voltage regulator. It it used so that fluctuations in electrical system voltages won't cause erratic gauge readings such as you're seeing. When you put more load on the system, the alternator is forced to increase it's output. During this time, the output voltage in the wiring from the alternator to the battery will be higher, which is why you're getting the temp gauge to rapidly rise. The temp gauge has a very narrow range of current flow in it to cause it to read from cold to overheated. Therefore, if the IP voltage regulator is faulty, your gauge will follow the electrical system's highs and lows, which you also have seen by changing your engine RPMs. In any case, check your battery voltage with all fans off, when possible, and make sure it is not too high. Depending on underhood temperature, the voltage should be around 13.8 volts. Higher if temps underhood are cold, lower if hot, such as in the summertime. When fans, accessories, etc., are on, the voltage should remain very close to the no-load voltage, with very little added engine speed needed to sustain it. If all this doesn't hold true, the alternator is failing. Of course, make sure belt is tight also.
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Old 12-05-2007, 05:29 PM   #8
Greg W
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Re: Temp Gauge Acting Weird

My 95 Windstar does the same thing on occansion. There are two different temp sensors one for the gauge and one for the fuel injection. My dash gauge would go to full scale sometimes but if I hooked up a Scantool the temp was normal. The sensor for the gauge is near where the upper radiator hose comes into the engine and a little beyond the EGR valve. It uses a 90 deg. push on connector. Mine was loose and wobbly. It can just barely be reached with two fingers to pull the rubber 90 deg connector off to check it for a good fit. If not then maybe the sesor itself is bad.
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Old 12-05-2007, 05:47 PM   #9
madmatt2024
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Re: Temp Gauge Acting Weird

Ok, makes sense to me. I'm good with electronics but cars are so complicated that troubleshooting can be difficult Were might this cluster regulator be? I'm sure this will be a dealer only part.
I am going to try replacing the sensor first, its only about $5 so its no big deal.
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Old 12-05-2007, 10:09 PM   #10
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Re: Temp Gauge Acting Weird

I checked my ALLDATA diagrams and test procedures and the bottom line is that if the temp gauge is not reading properly, or any other malfunction of the various readouts, the entire instrument cluster must be replaced. Of course there is always a possibility, however remote, that there may be a wiring problem associated with the cluster.
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Old 12-05-2007, 11:09 PM   #11
tripletdaddy
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Re: Temp Gauge Acting Weird

Replacing the instrument panel is a last resort to me. I haven't heard if you have ruled out the coolant temp sending sensor. Someone else had mentioned the test, but I will repeat it from my Haynes manual. First, turn on the ignition to run with the engine cold to see if it works at all. Next, disconnect the terminal connector from the unit and connect a jumper wire that is red/white to a good ground. This should make the temp guage go to max temp. If not, then the problem is in the circuit from the connector to the instrument panel. If the temp sender does seem to work reasonably. check its resistance. 10 ohms for hot and 74 ohms for cold. Outside this means its no good. You could stick in hot and cold water to measure its resistance change.
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