Water Temp Gage Erratic???

[dwbailey]

Thanks for the info mightymoose! I was noticing yesterday that it isn't bouncing around with acceleration like it had a time or two before. Sometimes it sits right where its supposed to and right when I think maybe its corrected itself, walla! It starts jumping around again. The heater works fine so I don't know where to start that would be the most likely thing to do first. I had hoped that the wire that was loose in that 2-pin connector that is next to the one that only has the threaded pin sticking out of it would have fixed it. It was pretty loose and it doesn't appear there is anyway to fix it since it looks like a gel type of stuff that holds the wire in. I jammed it back in and then stuck some electrical tape on it to hold but that didn't fix it. Of course it may still not be connected good inside the connector but who knows if that would even cause the guage to jump around. I just hate to start shooting darts in the dark.

[mightymoose_22]

You are not as much in the dark as you might think.
I believe you said you already replaced the sensor and had no change. That was the most likely culprit. It seems all your connectors are fine, and the odds that the gauge itself is bad are very slim.

What would cause the gauge to fluctuate? When the thermostat works right and holds the water back, the temperature should rise steadily until the thermostat opens. The temp should then remain steady. If that does not seem to be the case, then what you may have is coolant getting around the thermostat, either due to a leak or a bad valve in the housing.

This problem is best described as "overcooling", and you can find some lengthy threads about it in this forum.

Having done what you already have, the next logical step is to replace the thermostat and inspect the bypass valve in the housing at the same time. If the valve is bad, replace the housing and thermostat, slap it back together, and that's that.

With the symptoms you give, there really isn't anything else that could be the problem.

[mustang302]

Mine was acting very similarly, especially with the gauge bouncing around when I accelerated. The coolant hose and those two sensors are held by a bracket connected to near the engine / transmission junction by one bolt. That makes the ground connection for the coolant temperature sender. Try taking that bolt out and cleaning up the bracket and where it attaches, it fixed mine.

[Davescort97]

Clean up the ground. Whether you have gauge trouble or dim lights etc. it is almost always the ground.

[dwbailey]

Originally Posted by mightymoose_22

You are not as much in the dark as you might think.
I believe you said you already replaced the sensor and had no change. That was the most likely culprit. It seems all your connectors are fine, and the odds that the gauge itself is bad are very slim.

What would cause the gauge to fluctuate? When the thermostat works right and holds the water back, the temperature should rise steadily until the thermostat opens. The temp should then remain steady. If that does not seem to be the case, then what you may have is coolant getting around the thermostat, either due to a leak or a bad valve in the housing.

This problem is best described as "overcooling", and you can find some lengthy threads about it in this forum.

Having done what you already have, the next logical step is to replace the thermostat and inspect the bypass valve in the housing at the same time. If the valve is bad, replace the housing and thermostat, slap it back together, and that's that.

With the symptoms you give, there really isn't anything else that could be the problem.

I actually haven't replaced the sensor yet. Just looks like a new one so didn't change it. I would think that if the valve in the thermo housing was bad that when it opened when its not supposed to that the temp of the water in the system would not be so cold that the guage would go from around a quarter or so up the guage to all the way cold and bounce around would it? Isn't the water in the system when driving along pretty hot?

[dwbailey]

I do like the idea about the ground. Will try that. Hopefully the bolt is loose or something simple like that!

[tripletdaddy]

I didn't read earlier how fast your guage is bouncing around, but if it is really moving around a lot, even a slow temperature change over as long as say ten seconds, that's an electrical problem, either a ground or hot contact issue.

The response time of the electro-thermal conductor is not that fast. It isn't, because it doesn't need to be. So it isn't made to change much faster than coolant would when being heated and cooled in the engine. So any jumping around has to be by an electrical electrical problem.

[dwbailey]

Took a look and the temp sensor that is in-line in a hose doesn't appear to "bolt" to anything. It's just hanging in-line. Where would a bolt be that has anything to do with the ground?

[tripletdaddy]

If it has two wires instead of one, then one of the wires provides the ground. So, other than for stability, a bolt and bracket is not needed. It sounds like you described it as the one wire unit with a threaded stud to which the wire goes. This unit would require some means of an exterior method of grounding. I still believe your erratic guage problem is electrical in nature if the temperature swings are fast and great and will go totally to zero like it's off. What I could find in the Ford FSM and the Autozone.com repair photos, is not very clear. The temp unit screws into a metal pipe, but I can't tell if and how it's grounded. The FSM would make you think it is grounded through the pipe to the block, as indicated in the wiring diagrams, but from what I could tell, the pipe is connect to the block with a rubber hose, so no grounding. Try to figure out how it gets metal to metal contact for grounding. Try wiggling wires and other related things to the temp unit while testing for continuity to try to find the bad ground connection.

[zzyzzx2]

Originally Posted by tripletdaddy

If it has two wires instead of one, then one of the wires provides the ground. So, other than for stability, a bolt and bracket is not needed. It sounds like you described it as the one wire unit with a threaded stud to which the wire goes. This unit would require some means of an exterior method of grounding. I still believe your erratic guage problem is electrical in nature if the temperature swings are fast and great and will go totally to zero like it's off. What I could find in the Ford FSM and the Autozone.com repair photos, is not very clear. The temp unit screws into a metal pipe, but I can't tell if and how it's grounded. The FSM would make you think it is grounded through the pipe to the block, as indicated in the wiring diagrams, but from what I could tell, the pipe is connect to the block with a rubber hose, so no grounding. Try to figure out how it gets metal to metal contact for grounding. Try wiggling wires and other related things to the temp unit while testing for continuity to try to find the bad ground connection.

It's the single wire sensor that goes to the gauge. Therefore the bolt is part of the grounding, and could easily cause the problem.

[Intuit]

Originally Posted by dwbailey

.......... The car really cranks long when it is cold like it doesn't want to start and a couple of guys have said that maybe that sensor is telling the computer that the engine is warm when really it is bone cold and that could cause a hard start when its cold. Have replaced the plugs and wires and confirmed that the coil is hot hot. Any ideas guys? Thanks guys and Happy Thanksgiving!

Long Crank Time - Had the same issue with cold starts. I actually liked it because it gave the engine a good priming. To get an immediate start, try simply turning the key to the forward position right-before crank, then *immediately* after the you hear the fuel-pump quit, crank it. Should start right up.

Cause of the issue was the fuel pump allowing the fuel to run back into the tank when not powered. They normally keep the 30 or 40psi or so in the lines. Nothing to worry about really as this alone is not a sign of impending failure.

But if insist on repair, it's good to know that it's a simple job to replace the fpump yourself. (with a Haynes manual, common sense around fuel and basic tools) TIP: If it's in good shape (which there's no reason it shouldn't be,) hold on to the original rubber gasket that seals the tank and do a direct comparison for proper thickness, fit and size. If there is even the slightest mismatch, use the original instead of the replacement. Otherwise you might wind up with a fuel leak when you fill the tank back up. (there are some bad replacement seals floating around out there)

'94 Escort LX 225k