Rushifier

I've got a 1992 EG sedan with a D16Y7 swap. Automatic.

Anywho, the check engine light was on for the coolant temperature sensor, so I went to AutoZone to pick one up. I go in and ask the lady and she gives me the part, I go home and replace it. Start the car and I still have the CEL even after resetting the ECU, so I double check and it turns out the lady gave me the coolant temperature sending unit instead. That's fine except when I pulled off the little connector that goes over the end of the sending unit, it sort of cracked. No biggie. Seems to work anyways. I go replace the ECT and boom, no check engine light, but now my car seems to be overheating.

The gauge seems to rise to about 2/3 to 3/4 of the way to the H mark and hang out at that point, and no the fans weren't kicking on. I go ahead and check the connector to the fan switch and bridge it, boom fans come on. So I replace the fan switch and the thermostat and try again, now the fans kick on but the temp still hangs out at 3/4 of the way up. It then crosses my mind that I need to bleed the coolant. So I go ahead and do that for friggen hours and I think I got it pretty well bled, so I take her for a test drive. Now the gauge is in the half way mark but slowly creeps to 3/4 and then back down below half and it doesn't seem to have a pattern. It'll do it sometimes when at idle, sometimes when driving, other times with the heater on/off. Sometimes it just sits where it's supposed to.

What I'm wondering is if maybe the broken connector on the wire that goes to the sending unit could cause this fluctuation? If the car is at 3/4 to H and I unplug the sensor and plug it back in, the gauge will read right below half where it's supposed to for about 20 minutes and then creep back up. Also, it seems like the fans wouldn't kick in until the gauge was at 3/4 but after disconnecting and reconnecting the sensor they are on even when it's at half way. Basically this doesn't make any sense and I can't tell if my car is actually running hot or if the gauge/sending unit is just eating my lunch. Any help is appreciated.

Wankenstein

OP..do you take a breath when you talk? Insert some spaces and exhale.

Did it ever overheat or run hot recently before the CEL came on? From cold start how long does it take to get to the halfway mark on the temp gauge?

Maybe the thermostat is stuck halfway open/closed. Another possibility is a weak (failing) waterpump. From cold start remove radiator cap and run the engine until operating temp..watch the coolant inside the radiator for movement (rev engine). Coolant should be moving swiftly at top of radiator when revving engine and if not could be a weak waterpump. Would be a good time to check coolant temp with a hi-temp (above 200 farenheight) thermometer in radiator.

Whenn you bled the coolant did you have the front end up on jack stands as high as possible, climate control on max heat, blower fan off and rev the engine intermittenly to help bleed out bubbles/air?

Rushifier

Sorry, was typing all of this on my phone last night and it kept deleting it so I just ran through it quickly.

No overheating until I broke the connector to the sending unit. I already replaced the thermostat and the behavior is the same. And when idling and revving the engine, coolant gets pretty agitated in the radiator and spills over.

I haven't had a chance to time it from a cold start so I'll do that today and report back.

Rushifier

Here's a picture of the connector that broke, I am sorry if the picture is huge, I'm doing all of this from my phone and it doesn't allow me to change the picture size.

https://imgur.com/gallery/vgzo1

Rushifier

Update: just timed the gauge from start to correct temperature and it took 3 minutes and 10 seconds, it's 50 degreees outside here and the car has been sitting for 12 hours. That seems pretty damn fast to warm up. There is oil leaking from the dizzy onto the sending unit and connector though. I'll clean that up today.

ezone

Pretty much sounds like this is happening to you. You didn't have an obvious high temperature gauge problem UNTIL
It's pretty likely you now have a wrong, or poor quality gauge sending unit.

Reinstall the original unit and see what happens?


Also note, gauge is 25 years old, and old electronics can get flaky.
Looks like a lot of oxidation or corrosion in that terminal....might lead to high resistance in the connection which leads to incorrect gauge readings (lower than it should). Need clean shiny metal and a tight fit, for a good electrical connection.




Assuming you have a working stat and working fan switch and the system is completely bled of trapped air pockets......After warmup, the engine operating temp should stay in the range of 180F (or whatever temp the stat opens) to around 200F (fan runs).
You could verify actual temps with thermometer or infrared thermometer if you wish.

Rushifier

I threw the old sensor away, I know, bad move. Anyways, today the car seems to be at normal temperature all day so far. I did take off the connector and clean it up and put it back on, but like I said the plastic is all cracked and maybe it's not making good connection.

If I have a infared thermometer where's a good place to aim it? The block? Radiator? The sensor?

ezone

The plastic shell is just a protector. The terminal inside it is important.

Wankenstein

My 98 EX's similarly cracked (plastic) three years ago I cleaned the metal terminal and it's been fine since.

Wankenstein

Please get that O-ring replaced and oil leak stopped as soon as possible. Besides leaking oil on the ECT sending unit it's also leaking onto the heater hose underneath it and can degrade it and potentially cause bulging or tear in that hose that could lead to an overheat situation. Pull the distributor and check that hose.

Rushifier

Update:

I haven't had a bunch of time to work on the car until the last few days. I was able to previously replace the thermostat and the fan switch. I am still getting a mild overheating issue. No coolant in oil or signs of blow head gasket. I've bled the coolant constantly for days, there is never ending amounts of air when the fans come on, it sucks a bunch of coolant in and I have to add more. I literally did this for hours yesterday.

When the heater is ON, There are no bubbles and the fans don't come on. But when it's off, and I rev the motor, I get some bubbles for a minute. Also, the top radiator hose is VERY hot and the bottom is slightly less hot. I am really at a loss as to what's going on. The car drives no different no matter the temperature and the needle never reaches H, just about 3/4 of the way up.

Rushifier

Could there really just be that much air in the system? Even after bleeding for hours and hours?

Edit:

I've noticed that the system isn't pressurized, meaning I can remove the cap when the engine is hot and coolant doesn't shoot out. I am going to replace the radiator cap today. I am thinking that's where my endless supply of air bubbles is from.

ezone

This is NOT how you find a blown head gasket.
A head gasket can fail in any of a dozen (or more) different ways. You're only looking for one or two of those dozen+ ways.

THIS would make me think it's a blown head gasket.

I'd then run a test that would prove it.

Rushifier

I'm going to do a compression test today as well as replace the radiator cap.

ezone

I suppose your compression test shows all is well?

That probably needed done just to see what's good, but that''s not how I'd prove the head gasket problem.
This one sounds bad enough it would show up in a block test (blue or yellow fluid?) but I don't use that either.

If it's leaking combustion pressure into the cooling system, I pressurize the sealed combustion chamber and watch for evidence of leakage in the cooling system.