Losing Coolant, can't figure out where!

[seibman]

91 Nissan 240sx, I keep losing coolant but can't figure out where, I replaced the water pump and thermostat, the temp gauge goes up and down, sometimes I have heat and sometimes I don't even with the temp gauge pegged at hot. Funny thing is that the engine doesn't act like it is overheating. Also there isn't any coolant leaking under the car at all, whether it is under pressure or not....go figure!!

[evmal613]

im having the same problem right now. Most likely due to air bubbles. air bubbles can definitely cause overheating. It will take awhile for it to get out, if it gets hot, just let it chill for a bit, then check the temp and it should be ok. I just replaced my thermostat and water pump just yesterday, i hear ya man

[pj]

going into your oil or out the exhaust maybe? i dunno, just a thought

[jr_ss]

You've got a leaking HG or a cracked head... Do a coolant pressure test and see if you can figure out where it's going. You can also charge your cylinders with air and pull your rad cap and see if you have bubbles coming out of the coolant. One cyl at a time of course.

[seibman]

Hopefully thats it...as far as i know its not going into the oil or out the exhaust, possibly a good sign.

[Fibre guy]

Are you sure it isn't pumping into the coolant overflow while your driving? mine used to do that back when I had my KA.

[seibman]

never did before...although my tank does have a crack in it...but it does not leak out anywhere...I even put cardboard under the car and it comes out clean.

[Fibre guy]

Whats your coolant mix? If its just water it might be boiling out. Coolant normally flows into the tank while your highway or city driving with the change of engine rev and load.

[seibman]

I use the normal 50/50 mix...never just water, is it possible my engine has air trapped in it due to changing thermostat and water pump?

[LayNLow240]

Fix the leak and bleed your system using the bleeder screw. Take it out, let engine idle, when coolant flows out with no bubbles plug it up and top off rad and overflow tank.

[JS13240]

You should pull the spark plugs and check to see if there is water in the cylinders. Coolant runs through your intake manifold so a leak in that gasket could be making you burn the coolant off. It would also let air build up in the coolant lines and cause the car to overheat even after you bleed air out.

[Guappone240]

I had the same problem with mine. Check your oil and make sure it's not the head gasket. After that check your radiator. I spent a month and a half trying to figure out why my gauge was showing I was over heating, and I found out after it dumped all my coolent that my rad was missing the bottom 3rd of it. I was convinced that my rad was fine and the problem was else where that I completely over looked it.

[seibman]

Well, I bleed the air out and added more coolant...then took it for a nice long drive, so far so good...seems to have taken care of the problem..knock on wood... thanks for all your help everyone!!

[evmal613]

Tell me whats happening, i would really like to know if you are still overheating or not. Also, where is the bleeder screw located?

thanks

[seibman]

The car has been working great!! No overheating at all...the bleeder screw is located on top of the intake manifold in front of the engine, just follow your top radiator hose to the intake and you'll see it.

[Guappone240]

Good to hear. My problem got worse. Now I need a new head

[seibman]

That sucks dude...I wish you luck!! Let me know how you make out.