Runs hot/oil gauge acts funny

[Jason in LA]

‘96 GT, 160,000 miles on it.

The car just had a lot of work done on it. I got a good deal from a neighbor of mine that has worked on Mustangs. The car had a blown head gasket. Oil mixed with water was everywhere. He took everything apart, changed all the gaskets, changed the intake manifold(the old one was cracked), new water pump, and a new oil cooler adapter. The engine was cleaned up pretty good. The coolant reservoir still needed more flushing. He flushed it about 4 times. I decided to take over because I could do the rest myself. I flushed it out 3 times, and it was pretty clean. I then filled it up with coolant, and the car seemed to run a lot better than it was before he started working on it.

Here’s the two problems.

1. The car is running hot. It would go to the far side of the “M” in NORMAL, and the coolant light came on a couple of times. It was only on for a few minutes though. The coolant level in the reservoir was fine. I didn’t have the thermostat changed, so I thought that may have been the problem. When I went to change it I noticed that the old one had not been re-installed. I’d been driving around for about a week without one. I installed a 195f/90c thermostat, but that didn’t fix the problem. Today it went to the “A” of NORMAL when I was at a stop light. It went back to the “M” when I started to drive. One thing that I noticed that may be the problem, when I pulled the car over today, I popped the hood with the car still running. The fan was not on. I don’t know when the fan is supposed to come on, but that would seem like a good time for it to be on.

2. When I am fully stopped, with the car in drive, the oil pressure gauge drops to low, and the needle starts to bounce around on the low end. This only happens after the car has fully heated up. When the car is still cold the gauge reads normal. Also, when I put the car into park or neutral the gauge goes back to normal. When I start to drive the gauge goes back to normal. This problem only happens when I’m completely stopped and the car is fully warmed up. This problem was going on before I installed the new thermostat.

 

[Rerun]

I had similar issues. I've come to learn not to trust the stock guages, I invested in a water temperature and oil pressure guage from autometer. I had a lot more oil pressure than I thought.

I hot wired my electric fan so when I turn the key it comes on, it helped my heating problem. From what I understand, if you get hot while sitting at a stoplight and it begins to cool down when you're driving you're having problems getting air across the radiator. There's a sensor that's supposed to kick the fan on after your temp gets to a certain point, you might want to replace that.

I don't know, just some food for thought. Hope this helps in any way.

 

[Jason in LA]

Thanks for the advice. Do you mean replace the sensor or the fan?

Can I get the oil pressure and the engine temperature checked at a local shop?

 

[Jason in LA]

I let the car idle for a few minutes after I had driven it for a little while. At first the fan wasn't on, and the car was pretty hot. But after a few minutes it came on. I guess that might not be the problem. Or the fan is coming on too late.

 

[COramprat]

Mine always runs around the m on normal...It is...well...normal. Now if your coolant light comes on then you are low on coolent. Try adding water/coolent. Maybe flush out the system.