*Another* EA82 Cooling Sensor question....

[Tmckinl1]

Still tinkering away on this 85 DL with an EA82 and a Hitachi carb. To date, I've replaced half shafts, strut mounts, struts, sway bar bushings, plugs, wires, rotor, cap, fuel pump and filter, along with a new compressor and accumulator for the a/c. I ran the car that way a week or so (77k miles on it now) and I started getting an ECS Code for temp sensor. It also would cut out on me occasionally around 70 mph on the interstate acting like it was starving for fuel.

 

Today, I rebuilt the carb and swapped out the temp sensor. She started up and idled pretty good, but I noticed the temp gauge was climbing rather quickly, and after just a few minutes, it was in the "red" zone (no temp numbers on my gauge). The aux fan did not kick on either. I shot the temp sensor with my laser thermometer and it was about 190F. According to the cheapo Haynes manual I have, normal operating temp is 212F. With that in mind, I decided to take it for a test run. Runs much better at highway speeds with better acceleration on the top end, even made 75 mph with the a/c running. The temp needle never moved any higher (or lower for that matter), and I didn't get an ECS code, so I drove on home (approximately 20 minute drive). When I got there, I popped the hood and noticed the aux fan running as it should. I shot the temp sensor base and it was 202F.

 

All that being said, it appears to me that the "new" sensor for the gauge might not be working properly. It is the two spade connector, and with no ECS code, I'm leaning toward a faulty sensor. Temp needle rode just north of center with the old sensor, but of course it would end up throwing a code...

 

Anyone else have this happen? Also, am I incorrect about the operating temps?

[DaveT]

I can't be sure, since you have a version I have never seen.  I had an 86 with a carb, no ECU.  All of my others were & are SPFI.

 

On the SPFI, the ECU uses a 2 wire sensor for engine temperature.  It will cause all kinds of drivability issues when failing.  Often, without triggering a code.  The temperature gauge uses a 1 wire sensor.

 

On any of the Subaru engines, it is VERY important to fill and idle and check and recheck the coolant level before driving.  Often refereed to as burping the system.  Any time the coolant system is opened and partially drained, an air pocket can end up in the thermostat housing and or the water pump.  This can cause an overheat, which is risky for headgaskets.

 

Check the coolant level in the recovery tank AND the upper hose frequently, at least until you are sure that things are normal.  Don't open the radiator cap, as this introduces air into the system.  Sharply squeeze the upper hose, and listen for air / gurgling and the giggle pin in the thermostat.  Only open the cap to add coolant if it sounds like the upper hose is mostly air.

[Tmckinl1]

Thanks for the advice, I'll do those recommended checks as well. Did have a little verification that the sensor is off. After letting the engine completely cool, I turned the key to run without starting the engine. Temp gauge climbed steadily up to 3/4 hot mark with the engine cool, so I'm guessing the new sensor resistance value is not correct. I am going to order another sensor and I think I'll run this one for now. It's either run this one, with faulty indication but no ECS code or reinstall the old one, which seemed to give accurate temperature indication but throws a code. Car has ran better with the new one, but that most likely has much more to do with rebuilding the carb vs. swapping the coolant temp sensor.

[Gloyale]

Sounds like you put a fan thermoswitch in instead of a Sender.

 

IIRC, temp Sender should have only 1 spade.

 

Thermoswitch in the trans controls fans, noit teh ECU.

 

In fact, those old Feedback ECU's don't really do spoob other than vary the mixture by opening/restricting the air bleeds for the emulsions.

 

Disconnect that stupid ECU.  it will run much better.

[Tmckinl1]

Thanks. This particular coolant temp sensor is a two spade that drives the temp gauge, which seems to be different than a lot of information I've read. Unless the PO went to the trouble of replacing the single plug and sensor with the two spade plug and sensor (highly doubtful given the general condition of the car when I bought it) or maybe they ran the two spade plug on a single spade sensor??? Either way, I am a bit confused. Wiring and original sensor were both two spade, but everything I've read and heard says the gauge is driven by single spade sensor. Got me to doubting myself so badly, but I finally applied a little common sense and just unplugged the darn thing. Sure enough, I loose temp indication with it unplugged.

 

I'm with you on the aux fan, used that little fact to help me feel better about the false indication of an overheating condition. No fan running while gauge pegged high, ran her for a while and verified fan working.

 

I certainly will look into unplugging the ecu, maybe just reinstall original sensor and do that.....

[Gloyale]

So I just looked at the FSM, and apparently the California model 85 EA82's do use a 2 wire sensor.  But the 2 spades are not connected so to speak.

 

What I would do is turn the key on, and ground each of the wires in the connector one at a time.  Which ever one results in the gauge pegging to hot, is the gauge wire.  the other one goes to the ECU.

 

So you can install a standard 1 spade sender and just run that one wire to it and leave the other disconnected. 

[Tmckinl1]

Update: new *correct* sensor arrived yesterday....plug and play, so all is well with the temp gauge. Now I'm going to tackle the erroneous fuel indicator! I have a new tank to install, this weekend, along with rack and pinion and new cam belt set. Currently fuel gauge indicates 3/4 when full and 1/8 when it's really half full. When I swap the tank I'll work over the sending unit as well...

 

Thanks for the help/suggestions.