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Car was running hot today. Long story short, i plugged the laptop in to check and the ecu was reporting coolant temp of 223 degree's.

Yes, that's too hot. It shouldn't ever get above maybe 205 degrees Fahrenheit.

Even with the ECU reading 223, the gauge was at normal.

Story:
Driving to the bowling alley today, i look down and notice the needle awfully close to Red. I baby it down the road, the needle keeps rising. After a couple minutes, the needle plumits and returns to normal. About a mile later, the needle rises again but holds steady at about 3/4 the way up, nowhere near red but still above average.

When I reach the bowling alley, i shut the motor down and look under the hood for any signs of leaking coolant.

Then I plug in the laptop and start the car. The needle is at normal, the laptop reads 223. I let the motor idle and the laptop shows temps dropping as low as 206 but then goes back up to 223 before I shut it down and go bowl.

After bowling, I lift the hood and fill the coolant back up. It took almost a complete gallon to top it off. On the drive home, I carefully monitor the gauge and it never goes above normal.

This is the same type of shit that was happening before I pulled the motor and replaced the headgaskets. *sigh*

Hmmm I was going to say that maybe it was an air pocket, but if you had to add a full gallon of coolant I don't know...

How does your oil look?

Maybe the thermostat, did you change it when you did the head gaskets?

Gary

Yeah, new thermostat with the engine build... got the thermostat from SOA when I bought my engine gasket kit.

It seems to be a case of missing coolant. I would think it were thermostat problems too if I didnt have to keep adding coolant every 2 days.

Yeah...sounds like you were low on coolant....i've experienced air pocket issues like that.

So, Josh... when that happens... does the sensor then read the temp of the air trapped in the system instead of the coolant resulting in a spike of the temp gauge?

I cant imagine my engine actually operating with the needle in the red... and then when the needle does return to normal, it drops real fast... I dont think coolant could cool that quickly but im not sure.

So I before I left work today, i topped off the coolant. It didnt take much, maybe 1/2 a liter. Then I plugged the laptop in and kept it on Coolant Temp the entire drive home.

It stayed steady at 180 degree's most the drive. The highest it got was 199 but never passed 200. I live about 8 miles from home, i would say it was at 199 at mile 4, and by mile 7 it had settled back down to 185.

So yeah... that 223 I recorded yesterday was way high.

Whats your radiator cap look like?

Its brand new. I bought it at autozone tho, they looked up one for a '93 Turbo Legacy.

It looks like its silver with a red tab in the center you lift to relieve pressure. Been thinking of going to SOA and getting a new one from them though since it seems you can never trust aftermarket replacement parts these days.

I'd recommend getting an OEM radiator cap.

The coolant temp sensor isn't really going to read air pockets that well, at least I wouldn't think so. You probably had some pockets of hotter coolant that caused the temp spike.

The temp sensor is in a place that is not susceptible to bubbles, in the coolant crossover pipe, just before the coolant enters the engine.. The bubbles get trapped just behind the thermostat, creating a buffer from coolant and heat. Lack of heat and hydraulic pressure(from the coolant) causes the thermostat to stay closed. Because the engine and radiator are separated by the thermostat, the engine will be much hotter then what the temp gauge reads, and the radiator fails to cool the motor.

I think you need to bleed your system and try again. And get an OEM cap no doubt. Because you over-heated, you have to be uber-carefull to check for signs of headgasket failure. Our motors do not like to get hot, thats why they crack heads.

Yeah im gonna be pissed if I blew a headgasket. I just replaced the head gaskets and got the motor in and running. Havent even got a full tank of gas through the new build and im still having trouble.

I guess I gotta search on bleeding the system and see if there is something im missing.

Arctic Assassian wrote:The temp sensor is in a place that is not susceptible to bubbles, in the coolant crossover pipe, just before the coolant enters the engine.. The bubbles get trapped just behind the thermostat, creating a buffer from coolant and heat. Lack of heat and hydraulic pressure(from the coolant) causes the thermostat to stay closed. Because the engine and radiator are separated by the thermostat, the engine will be much hotter then what the temp gauge reads, and the radiator fails to cool the motor.

I think you need to bleed your system and try again. And get an OEM cap no doubt. Because you over-heated, you have to be uber-carefull to check for signs of headgasket failure. Our motors do not like to get hot, thats why they crack heads.

That's not correct, coolant flows from the bottom of the engine, through the engine, up and out the crossover pipe and then into the radiator. That is a relatively high spot where air could get trapped, as coolant flows faster it'll move the air pocket to the vent spot that dumps back into the expansion tank.

Yeah i was wondering about that. The thermostat is at the lowest part of the engine while the thermo sensor is almost near the upper most part.

I can see how when my coolant gets low it could read a false signal. However, i still dont like the thought of my engine running that high.

It shouldn't. The ECU regulates the temp between 180-200 deg F

Yep I was backasswards. So what on earth caused this? It wasn't a bubble, was there just not enough coolant?

Sounds like there just wasn't enough coolant. Especially if you initially had to add a full gallon to it.

I find myself adding about a liter every 2 days.

I brought a coolant system pressure tester home with me from work. Im going to see if I can preasurize the system and check for leaks.

when you had the heads off did you have them pressure tested?

if you are putting in a 1/2 liter every day, its obviously going somewhere. does the car smoke at all?

Pressure test the system and the radiator cap. I have the test pressures in a thread I started not to long ago in here.