Thread: Overheated last night - doesn't want start today

Did the cold compression test last night. Held the gas pedal down and cranked the engine 5 times for each cylinder. Did I do the test procedure correctly?

cylinder 1 - 190
cylinder 2 - 190
cylinder 3 - 170
cylinder 4 - 190

I'm going to do another test tonight. Just to back up these numbers.

I also ran self diagnosis on the ecu to see if there were any other codes besides code 95. The check engine lights always on due to the wrong Fidanza flywheel on my b14 that always throws a code for the crank Position sensor (code 95). Code 32 (EGR) also came up - 3 long flashes followed by 2 short flashes.

Yuadman

Did the cold compression test again. Held the gas pedal down and cranked the engine 3 times for each cylinder and hear are the results?

cylinder 1 - 148
cylinder 2 - 152
cylinder 3 - 130
cylinder 4 - 160

Cylinder 3 is lower than the rest once again.

Yuadman

The plugs have about 30,000 km (18,500 miles) on them. I was getting good fuel mileage out of these plugs. I usually get about 7.5 litres per 100 km - 80% highway.

Yuadman

I usually crank the engine until the pressure on the gauge stops rising. You need two people usually for that, one to watch the gauge, one to crank the engine. Your 5 crank numbers are probably way more accurate and reliable than your 3 crank numbers. There's something going on with cylinder 3, but it doesn't look nearly bad enough to be causing your starting issues. It looks like your engine is at least okay. It's not great, but it doesn't warrant replacing or anything if you ask me based on the compression numbers alone.

Time to start diagnosing other things that would cause the problem and assume the engine block and head are in good shape. (Although maybe there is a little issue with cylinder 3.)

I changed the plugs, connected a egr tube that had become unconnected, changed the T-stat, flushed the coolant out with tap water and added new coolant & distilled water.

When I started it up yesterday afternoon it need some throttle to get it going. Once it got warmed up it idled as usual. The temps on the Nissan dataScanner read 217 after 5 minutes with the engine running with the rad cap off. The temp gauge in the instrument cluster indicated that car had not reach normal operating temperatures. I'm starting to think that the main problem is a bad temp sensor as a few of you have suggested. Why else would the data scanner reading be that off.

Later in the evening I decided to take the car for a 5 minute test drive to see how it would run. It started on the first crank with a ruff idle that became smoother as it warmed up. Once again the Nissan data scanner temps rose quickly and the temp gauge in the instrument cluster read normal. Drove the car to the gas station, shut the car off, added some air to all 4 tires, started up with no issues and drove home. Nissan DataScanner was reading 230 - 235 and the temp gauge in the instrument cluster was reading normal. Car seemed to be operating normally. When I got home I opened the hood to see if I had any leaks. NO Leaks.

After this test drive the odd thing is the upper rad hose is warm but the lower rad hose was barely warm. Should the lower hose be somewhat warm if the new t-stat is working correctly? I tested it in boiling water before installing it and it opened up. I also tested the old T-stat last night and it opened. So there goes my theory that the t-stat had failed and was stuck closed and caused the overheating.

Yuadman

Yes as long as you're up to temp.


It sounds like the coolant temp sensor that feeds data to the ecu (not the one that feeds your dash gauge) is reading too hot. That could cause your starting issues as you wouldn't be getting enough fuel during start-up while cold.

You've probably figured that out already though. If you can spare the time and money, try replacing the coolant temp sensor (the one with multiple wires, not the single wire one) with a new OEM unit from Gspec.

How long do these temp sensors last? Should they be replaced every 50,000 km? I know I've replaced it a least once or twice over the last 4 years. Where can I buy the sensor - Dealership or auto store?

Yuadman

I think they are supposed to last a long time. 100k+ miles or so. But they go bad seemingly at random. You should get a new one exactly where I told you to in my last post.

Took the car for another short 5 minute test drive. It 23 degrees Celsius outside so the car should be reaching normal operated temps in a short time period. Well the upper rad hose is nice and warm and the lower one that goes to the T-stat is not warm at all. What da @#$% is going on.

Could the rad be cogged? The thermostat is brand new oem and I tested it before installing. Anyone have an idea what's going on?

Yuadman

When you changed the thermostat, did you make sure the jiggle valve/air bleeder was up?
Did you bleed the system properly?

If there's an air pocket trapped around the thermostat, and the air bleeder
is installed down, it might not be transerring enough heat to the tstat to
make it open?

With the system cooled down, remove the air relief plug on the tstat housing,
just above/right of the water inlet. You'll have to take off the water inlet to
see if the tstat is installed with air bleeder up. If you do that, make sure to
bleed the system.