1993 Sentra SER - Cooling system / heating woes

[elvis240sx]

Ok, so the car is a 1993 Infiniti G20 w/ engine and trans from a 95 G20T. I recently had a leaking waterpump (from weep hole). So when I was changing the waterpump, I also changed the thermostat.

After the job, the car wouldn't get up to full operating temperature and the heat seemed warm, not hot. I let it run for a long time ( about an hour) with the radiator cap off. This did not help.

The next day I had no heat whatsoever. It would warm up to just barely the cold mark on the gage, then drop way off to nothing once I started moving.

I figured this was a stuck open thermstat. I changed the thermostat in the parking lot at work. I was also able to find the bleeder screw (near the thermostat housing). I threw the new thermostat in and ran the car with the bleeder screw out. It would kind of squirt out of the bleeder screw, but never seemed to flow coolant steadily. The car got up to temperature and had good heat pretty quickly after this though! I figured everything was fine.

Unfortunately, I didn't do a good job with the RTV on the thermostat housing or it was too cold to cure properly (it was about 18 degrees F that day). I had a small dripping leak at the thermostat housing. I ran the car for about two weeks with the leak, just topping off the system as needed. The heat stayed really good and the car ran at the proper temperature.

This weekend I got my garage nice and warm and resealed the thermostat housing with RTV. I let it sit overnight this time before filling the system. No leaks. I ran the car for a while again to bleed the system.Once again, I never got coolant to pour out of the bleeder hole. It would squirt out but not alot or not steadily. The car was running just a little bit under normal operating temperature. I figured it was because the cooling system was fixed and cooling so well. LOL

Today I wake up, and no heat. Car won't reach full temp. It was very cold this morning, about seven degrees. When moving, the temp and heat drops off completely.

I got a radiator cap with a funnel on it and filled it up and stuck it on the radiator. I ran the car with the bleeder screw out and the front end up on a jack. It reached full temperature according to the gage. Still, coolant would squirt out of the bleeder screw, but wouldn't flow steadily. The heater was not putting out hot air, but it was luke warm. Lots of bubbling from the radiator cap into the funnel. Car at normal operating temp. I ran it for about 30 minutes and put the bleeder screw back in. Then really good heat was flowing from the heater. The funnel stopped bubbling so I figured all of the air was out of the system. Car is at full temp, good heat. I start to drive away, and as I reach speed the temperature and heat drop way off quickly. If I sit at a stop for a long time idling the heat will creep up eventually to almost halfway. But when I start moving, the temp and heat completely drop off and cool way down.

What do these symptoms point to? I keep thinking I have a stuck open thermostat. But both were brand new. Would air being in this system cause these problems? I would think it would make me overheat?

Am I doing the bleeding procedure wrong? Should the radiator cap be on or off when the bleeder screw is out? Shouldn't coolant pour out steadily from the hole? Do I just need to keep running it until coolant flows from the bleeder? No, this car does not have the bleeder plug in the heater hoses from what I can see.

Help! It is way too cold to not have heatThanks!!!

[Q45tech]

Nissan oem thermostats? Sure you didn't install backwards?

[elvis240sx]

Already tried that. Thermostat won't fit in backwards. First one was a Stant thermo, next one was a NAPA. I tested the Stant thermo today in boiling water and it open up beginning at 172 degrees and fully open by about 185. It closes fairly rapidly once removed from the water.

[elvis240sx]

Ok, more attempts at bleeding the system.

I put the front end up on ramps. Car is nice and warm. Remove radiator cap. As soon as the bleeder screw is taken out, coolant starts to bubble and shoot out of the radiator!! No coolant comes out of the bleeder screw.

Next method. I leave front end on ramps. Remove bleeder screw with radiator cap still on. Car gets up to temp, great heat in cabin, and coolant comes out of the bleeder port. It is not perfectly steady, but flows for a few seconds, then stop, then starts again and so on.

Still, once I hit the road for a while the temperature of the engine drops off quite a bit. Now it at least stays above the cold mark with decent heat. BUT, it has been much warmer here lately. I think that has more to do with my somewhat success.

Is there another problem here like bad head gasket? Possibly air from the cylinders being forced into the cooling system?

Am I doing this bleeding procedure completely wrong? I mean when I have a coolant leak, the system works great. Car gets up to normal temperature and heat works great. When there are no leaks in the system, I am running super cold. Low engine temp means I stay in cold start fuel enrichment mode and get terrible mileage.

Any advice / help ? I must be doing something terribly wrong here.How about a bad radiator cap? Could that be it? LOL I hate throwing parts at my problems but this car is getting the best of me. My SR'ed 240 never breaks down, my stock SR G20 has nothing but problems.

[elvis240sx]

Car is fixed !! Woot !

Here is how it happened:

I took the high pressure radiator cap from my 240 and put it on the G20. I then noticed a coolant leak. Not very large, but it was losing pressure / small coolant from a line near the intake manifold. Fixed that.

Next part. I bought a 10 degree hotter thermostat. When talking to the guy at Advance Auto, he mentioned having the same problem with his mustang. Turned out his thermostat fell out of the groove and left a gap between the t-stat and the housing. Even when the thermostat was fully closed, water could rush past it and through the radiator. Never got up to temp.

I picked up a paper gasket along with my hotter thermostat. Pulled it apart, and holy crap he was right ! I must have knocked the thermostat out of place when lining up the housing with the RTV on it. I tacked the new one in place with a small dab of super glue and bolted the housing on with the paper gasket (no need to wait for it to dry). Fired up the car, filled the coolant and let it run for a while. As soon as I started the test-drive it was clear the car was fixed. The hotter thermostat rocks too! I have never had such great heat in this car.

What a stupid problem to be hooked on. Oh well, live and learn. I bet Nissan / Infiniti put out a tech tip on this at one time haha.

[elvis240sx]

PS. I am still disappointed in the bleeder screw on this engine . Even with great heat and no air bubbles in system, coolant never steadily pours out of the bleeder when engine is running. With engine off, it does pour out steadily. Weird