Just so you have the details on the car. It is a '90 GT with 43K original miles and the car is stock except for 40 series Flow Master, NGK plugs, MSD cap/rotor/wires and now a high flow water pump.

Yesterday I decided that I should replace the water pump because the one on the car was obviously the stocker, especially with the ordeal I experienced trying to remove the water pump gasket once I removed the pump. The coolant was not disappearing but the weep holes (both of them) were a little wet and I thought it was only a matter of time before complete failure. I found a high flow GMB reverse rotation pump at Checkers and it was a good price and included a lifetime warranty so I went with it. I also bought a replacement 180* thermostat (Prestone). After I got the pump and thermostat installed I was curious to see the temp difference if any. I started the car and let it idle for about 25 minutes in my garage and the temp never passed the 1/3 point with the headlights on (hahaha) I believe that is around the letters M and A. So this morning I wake up early so I can stop to get gas and Starbucks on the way to work to only experience three spooky but similar events. After driving about 5 miles the temp gauge (stocker) climb past half and went to the line above - I have never seen it go that high since I have owned the car. The typical level is half way unless headlights were on then it would get as high as two needles widths above mid-point. I did some reading and found that the headlights being on does affect the reading on these POS gauges. So, after the first incident I pulled over with the fear that I was going to over heat but I was surprised. I found that the radiator and hoses were hot but touchable engine was not ticking like it was too hot and I did not notice a drop in coolant (overflow), see any coolant or smell any coolant. After about five minutes I start the car back up and the gauge is below half. To make this longer story shorter, this happened two other times before I got the car back to the house but the final two times I stopped, turned off the lights and let the car idle and the temp eventually dropped below half each time. So after I got the car in the garage I jumped in the Sentra (I know - shut up) and headed to work.

After work I immediately assessed the coolant level and found that everything appeared normal. I removed the cap and started the engine so I can monitor the situation a little more. I did not find any other issues that I did not see the night before while the car was idling. I had a friend rev the car to about 2k rpms and I did see the coolant flowing in the radiator. After being scared three times this morning I decided to replace the Prestone t-stat with a 180* Mr Gasket (it came highly recommended). After replacing the t-stat and topping off the coolant I decided to take another drive. It was dark and the temp was about 75* outside. I noticed that there was a similar pattern but I refused to stop or turn off the car. I noticed that it would go to the line just above half then drop below half - cycle taking about 5 minutes each time. I also noticed that my oil pressure appeared to be higher than normal on the stocker gauge - it was about half way during idle after the car was warm. The volt gauge has always read slightly above half since I have the 3G 130 amp alternator installed.

So, the question is do you think that the problem is really a problem (i.e. wrong direction flowing water pump) or do you think this could be as simple as the gauge voltage regulator?

Oh, I used an infrared thermometer on the valve cover, t-stat housing, upper/lower intake, upper hose, lower hose and various points on the radiator and never received a reading above 220*.

Please help I am getting desperate and don't want to replace the pump again.

 

as long as you installed the pump according to the instructions than you should be ok. I installed a Mr gasket 180 degree thermostat and they act funny in the beginning. the temp will go up to 2 lines real quick and then the needle will drop suddenly to the first line. this is normal because the thermo is opening up and you will see fluctations. as long as your temp stays below 3/4 you are ok. headlights will not cause your system to heat up, only A/C does this because it robs lots of power. anyway, as long as you installed the componented Correctly than you should be ok. i hope you installed the thermo with the right orientation and not reversed. hope it helps.

 

Dbeck002,

Thanks for the input. I did install the pump correctly and the t-stat was installed the correct way with the point facing the radiator. I was thinking that the t-stat may act a bit funky for the first few drives but I was not sure how credible that idea was. Oh, I did not mean that the lights were causing the car to get hotter. I was referring to the known gauge issue that when the lights are on the gauges seem to read a different value from when the lights are off. I am going to look for a new after market gauge today and see if I can get it installed.

Aloha

 

get a mechinal gage and install it ...and see what happens

 

This morning I went out to the garage to look at the radiator level and found that it was to the top. I also glanced at the level in the over flow bottle and it was in the middle of the high and low lines. So, I decided to jack up the drivers front side to make the filler neck higher than the rest of the system and ran the car until it got up to running temp (radiator level dropped some) then I pinched off the over flow hose and filled the radiator with distilled water to take up every possible space that air could remain then quickly placed the cap back on.

I think I have the problem resolved. I drove the car again today during the day with temp outside near 80*. I tried driving with and without the headlights on and with A/C running and without. The temp remained a few needle widths beneath the middle line but once it went up to between the middle line and the line above it but it quickly returned to the below middle position where it remained.

Now, what size gauge is recommended to place them in the area just beneath the stock stereo? I was thinking 2". That should be a good location for a mechanical gauge for cooling temp and oil pressure. I really like the brackets that use the air vent but I do not want to obstruct the flow for the A/C because it gets too damn hot here.

Mahalo and Aloha.

Scot

 

wholeeeeeeeeee lotta reading... did you run your car for a while and let it get to operating temp WITHOUT radiator cap on? so when thermo opens up, coolant drops, then you can refil it.... so no air is in system? .... you could try and back feed it.... either way if you instaled the right pump for the car then there should be no problem there... as for headlights makin your temp go up, ive never heard of that.... dont do that for me

 

nemethjames1 - If you read all the "wholeeeeeeeeee lotta reading" you would find out that I did this not once, not twice but a total of three times. I do believe the issue is now resolved. I may just bleed the system one more time for good measure.

Aloha

 

go to www.autometer.com and look at the different gauge mounting methods they have for installing various gauges. you can get mounts to go on the A pillar using smaller gauges or you can go with 2-5/8" gauges mounted in the center AC vent which is what I did on mine. you still get plenty of air out of the other vents to keep your cool! and you can mount two or three gauges in this area also. I think, but not positive, that the two gauge pod lets you still have air blow out the vent too, but you need to double check this.

 

I am having a very similar problem with my stang. I pretty much know I don't have the reverse rotation water pump on mine.The guage goes to about 2 lines under overheating while driving.When im sitting in traffic the guage drops 1 to 2 lines while sitting idleing.When I start driving again it raises again.It really doesn't really matter whether my electric cooling fan is on or off.I mean with the fan home when I turn off after pulling in the driveway. I turn it off and roll the windows up and turn off lights and stuff.Then I look at the guage and it dropped 2 lines just from sitting at idle.If i left it running to long at idle with no fan it would overheat.

 

mustang8719 - you have to try bleeding the air from the system. It worked for me but I had to do it four times. Try jacking the driver front and with the cap off run the engine until the stat opens. Once the stat opens the coolant level should drop some. After the level drops some you can pinch the overflow hose, add some coolant as close as you can to the filler lip and while holding the overflow hose pinched replace the cap to prevent the level from dropping from the coolant that you just poured in from escaping too soon down the overflow hose.

After doing this take the car for a drive and it should be somewhat better, unless you are certain you have the incorrect pump. Also, what t-stat are you using? Has it been tested or replaced recently?

I hope this helps.

Aloha