Weird coolant/temp. sensor problem

[2_fast_240]

I just got my rebuilt ka in and running but my temp. gauge isnt working right. It takes a while before the needle moves at all and then when it does it is constantly moving. It never goes all the way down and sometimes it stays where its suppose to for a whole trip but its unconsistant. Also, the engine is losing coolant somewhere but its not leaking. When i take the radiator cap off theres about an inch of foam at the top. I loosened the head after I torqued it down to get that other cover on but the manual said to do that anyway. The air out of the vents actually seems to warm up with the temp. gauge but I know it doesnt take that long for the engine to warm up.

[Gnnr]

Bleed the air out the system as per the FSM and find that leak. Also your thermostat may be sticking. Change it with an OEM one from the dealer.

[prsfan01]

My temp gauge on the s13 has never seemed to work properly. I changed the thermostat a few thousand ago...no difference. I just hope someone can help it before I have a problem...Any other options for me?

Thanks

[2_fast_240]

The engines got over 2000 miles so i figured all the air would have worked its way out by now but ill bleed it anyway. I dont think its the thermostat because the temp. gauge goes down after running for like an hour. One minute it will be almost completly down, then the next it will be at the normal position and so on. It seems to me like it would just take a while to warm up if the thermostat was sticking open. And the temp. gauge has never moved past the middle.

[Gnnr]

Well, definately get an aftermarket temp guage. Analog or digital up to you. Anything is better than the stock one, that isn't very informative.

[scottyb]

The temp gauge gets its reading from the Thermal Transmitter, its a single spade connector somewhere near the Coolant Temp Sensor. The Coolant Temp Sensor only sends a reading to the ECU, its a double pin connector. Here is a pic from my RB, the connectors should be almost identical on the KA. This problem has nothing to do with your temp sensor or your thermostat, its your gauge, the thermal transmitter, or the wiring in between.
http://i88.photobucket.com/albums/k167/sbernhard83/CarStuff151.jpg

[2_fast_240]

Oh, sorry for the misuse of words. When i first drove the car after rebuild the temp. gauge wasnt working at all. The motor is a 97 and the car is a 91. So i took the thermal transmitter from the old motor and put it in the new on and it started working but not too good. I never had a problem with this before the old motor came out and its using all the same stuff. I guess theres always a chance something went bad at the exact same time I put the new motor in, so ill look into all that.

[2_fast_240]

Does anyone have any idea what would cause the coolant to foam up.

[scottyb]

This is sort of a guess, but the foaming sounds like there is air getting mixed in somewhere, like it isn't filled or bled all the way. When you initially fill it up and bleed it the FSM tells you to "race" the engine up to 4000 rpm several times in a row after the thermostat has opened iirc. This makes sure the pump builds enough pressure and flow to get all the air out of the heater core and top of the engine, you must have your heater on when you do this. I would imagine that in 2000 miles you've already worked all the air out, but maybe not.

[92FireCoupe]

I had a similar issue on my 240. I replaced the temperature sending unit and it works great. Try that it's 90 percent guaranteed to work provided you don't have any air in the system.