Guage Problems?

**RagTop** · 06-13-2012, 08:45 AM

My 2000 Z28 has 135K miles on it and is still strong. The other day I was driving about 100 miles in low 90s temps and I noticed that that the temp gauge was sitting just at the 210* mark. The car normally runs about one needle width below that mark. During the course of the trip I stopped and added some water to the expansion tank, but that didn't help. In fact the temp gauge went up beyond the mid point mark toward 260* at one point. I ran home with the heaters going to drain heat, and that seemed to work. I also noticed that the oil pressure was sitting at 40 psi when running at 75 mph on the highway. That seemed sort of low. The car normally idles at about 40 psi. I took it to my trusted mechanic and he diagnosed it as a leaking water pump. $1,200 later I was on my way again (water pump, new irridium plugs and wires). Yesterday the car did the same thing with the temp going all the way up to about 225*, and, significantly, I noticed that the ammeter was showing serious discharge at idle way down to the red area. I have the rotten problems with my radio and power windows caused by GMs crappy solder joints on the internal control box circuit board. Is it possible that all these problems are driven by some stupid electrical problem and are not real at all? The car shows no other symptoms. BTW, we moved those 100+ miles since the problem reared its ugly head, so I can't practically go back to my mechanic, who I am not feeling really warm about anyway. Help! I bought this car new and I still like it a bunch. If this is a real problem it could be fatal to my engine.

**FinZ28** · 06-13-2012, 10:12 AM

Sounds like you might have a few things going on, maybe. If your oil pressure is good enough to drive it, I'd drive the car to the nearest auto parts store and have them test the alternator. These cars start doing weird things when the voltage starts getting low. Any flickering of the headlights or dash lights at night when you're, say, stopped at a traffic light? As for your oil pressure, I'd stick a mechanical gauge on it to see what's going on with the oil pressure. Remember, the gauges in the '99-'02 F-bodies are electrical and not mechanical, so the readings aren't precise. As far as your car running hot, I would go back to the mechanic who changed your water pump out and take it up with him. If he didn't flush all the old coolant out you might have an air pocket somewhere. I would also think he would have changed your thermostat out, which is something else to check.

**RagTop** · 06-13-2012, 11:26 AM

I forgot to mention the thermostat. That was changed out too, as were the belts and plug wires. I've got a call in to the mech, but he's about 130 miles away now. Thought he might help out with the trouble shooting.

**JayTA98** · 06-14-2012, 05:47 AM

See if the mech or someone that has a scanner with live data can check the temperature with the scanner. If the scanner show different temp you might have a bad gauge or sensor. Have you checked the level in the radiator and coolant reservoir? Are they going down? If the radiator is low you could have a small leak or bad radiator cap. Make sure the mech does a pressure test on the system and flushes all the old coolant out if it hasn't been changed lately.

**RagTop** · 06-18-2012, 06:44 AM

I solved the problem. Last fall I lost the right front factory ground effect on the freeway. When I priced them they were $750 from GM. I replaced the whole front ground effect with an RKSport unit for less than $200. It is a one piece with a narrow center section rather than the open area that the factory two piece provided. It actually looked better than the factory parts. I finally realized that the temperature and oil pressure readings I was seeing were consistent with a hot engine. In addition, the ammeter going strong discharge was being driven by the computer, which was sending an overboost message to the electric fans to try to save the motor. Then I remembered the RKSport front ground effect and realized that, at high speed, it was causing so much turbulence in the front center of the car that it was denying air flow to the air dam that provides air to the radiator. I yanked off the RKSport piece and my Camaro returned to absolute normal. BTW, RKSport does sell an extended height radiator air dam, but they don't say it is necessary with the spoiler that I put on my car. Besides, because of the long overhang ahead of the front wheels, the stock height air dam hangs on every curb, concrete tire stop and sidewalk where I park the car. I can't imagine how annoying the RKSport extended unit would be in normal use. I'm glad I sorted this out before it destroyed my LS1. Thanks for you help and comments.

**FinZ28** · 06-18-2012, 09:16 AM

Glad to hear you got it sorted out. Crazy how things like that can cause issues.

**Smittro** · 06-18-2012, 03:20 PM

Originally Posted by FinZ28

Glad to hear you got it sorted out. Crazy how things like that can cause issues.

figures,,, the one post i deside to skip is the one where it's already fixed.. DERP!

**FinZ28** · 06-18-2012, 03:57 PM

Yeah, I was wondering about that lol.

**Smittro** · 06-18-2012, 04:17 PM

Originally Posted by FinZ28

Yeah, I was wondering about that lol.

It's all good I pulled the post..

**FinZ28** · 06-18-2012, 06:27 PM

You should have just edited it. The info about the coolant was actually pretty informative!

OP, did this by chance resolve your oil pressure readings? I know you said it was running around 40psi while you were driving at 75mph (my gauge indicates closer to 60-65psi at that speed). Like Smittro and I previously stated the gauges in these cars aren't exact, so it would be good to know everything is okay before something else crops up.

**RagTop** · 06-19-2012, 08:37 PM

Originally Posted by FinZ28

You should have just edited it. The info about the coolant was actually pretty informative!

OP, did this by chance resolve your oil pressure readings? I know you said it was running around 40psi while you were driving at 75mph (my gauge indicates closer to 60-65psi at that speed). Like Smittro and I previously stated the gauges in these cars aren't exact, so it would be good to know everything is okay before something else crops up.

The oil pressure is still on the low side. Once the car is warm it runs at about 40 psi no matter what speed I'm driving at. My car is an A4 car with 2.73 gears, so the rpm at highway speed is pretty low, but I am kind of concerned about the low op. Perhaps it is reflecting worn bearings. I'm thinking I should step the viscosity up to maybe 10W40 synthetic. I'm running 5W30 Mobile 1 now.

**Smittro** · 06-19-2012, 08:48 PM

Originally Posted by RagTop

The oil pressure is still on the low side. Once the car is warm it runs at about 40 psi no matter what speed I'm driving at. My car is an A4 car with 2.73 gears, so the rpm at highway speed is pretty low, but I am kind of concerned about the low op. Perhaps it is reflecting worn bearings. I'm thinking I should step the viscosity up to maybe 10W40 synthetic. I'm running 5W30 Mobile 1 now.

I would seriously consider checking the actual oil pressure with an after market guage..

These gauges only has the accuracy up to mearly letting you know you have pressure and should never be counted on as accurate.

The non-fluctuation is a common issue in these cars, and happens to the 3800 v6 models as well as the LS1 models.

Mine used to hold exactly 40 psi on the stock gauge at any given rpm..

I used an after market analog OP guage added before the factory sending unit and quickly found I had a useless factory guage.

The second guage showed full movement and also shown to have prefect OP operation.