Help! 1993 Overheating and "rattle"

[Vetteman-93]

I have recently purchased a 1993 Convertible 6 speed with 62000 miles on it. Car runs great except for two things.

1. When I am in heavy stop and go traffic or stopped and just idling, the temperature gauge climbs to a very high level. I can bring it back down by turning on the heater, revving the engine a bit, or moving the vehicle. I have had the thermostat replaced and the cooling system checked and all seems OK but it is not. Any ideas?

2. I have a heavy sounding rattle when I hit a bump or manhole cover in the road. It sounds like it is coming from the passenger side, just to the rear of the door and in the upper area of the rear quarter. I have had three shops looking for this noise but they all say everything looks tight. The noise from the "rattle" is ear piercing and I am concerned driving at high speeds.

Any comments are appreciated.

 

[2VettesMike]

Temp

If the AC is on or the temp will run 195-200F most of the time when moving. In traffic it can climb to 200-210. If the AC is off the fans don't run full time only when temp switches indicate. I am pulling from memory but the first temp switch doesn't turn on until 228F. These cars run hotter than small blocks you may be used to and it is normal. One other area to check is in front of the radiator at the bottom for leaves and higher up in front of the fans for grass, debri, etc. The upper part can be reached with a long brush from the right side of the radiator. These cars are bottom feeders for air and the radiator front needs to be cleaned every year or two.

As for the rattle that is hard to tell in a forum setting. Could be loose bolts, bad wheel bearing, worn ujoint, loose inner fender panel.
You will just have to tap around and see what you find.

Good luck,

Mike

 

[Tuna]

Please quantify the temps you are seeing.
Coolant temps up to 230-235 while sitting in traffic on an LT1 are not uncommon so long as they drop once the car is moving again.
Also, check for plastic bags and other debris on the radiator. They get sucked up there pretty easy and, if at the very top, they can be hard to see.

The rattle is hard to comment on in a forum. I had a rattle years ago in my ex '92 LT1 and it turned out to be the converter - the insides were coming loose and rattling around pretty good, sounded like rocks in a tin coffee can being shook hard.

That's my 2-cents.

 

[Hib Halverson]

If you're reading coolant temp from the anolog gauges, know that they are horribly inaccurate. It's a design defect of the 90-96 instrument panel. In fact, in later years, the cars came from the factory with little stick on the cluster which warned the owner of that problem.

With a 93, use the "gauges" button at top right of the cluster to put coolant temp on the digital display under the speed read out. That number is the actual temperature. Others who've posted here have given you the range of temps to expect.

Since you bought the car used, you also need check two other situations relating to cooling.
1) Remove the top of the cooling stack and inspect the area between the HVAC condensor and the radiator for debris/trash between the two which restricts air flow. Clean that are as necesary. Then inspect the front of the HVAC condensor for debris/trash stuck in or stuck on the front of the condensor.
2) inspect the front air dam. If it's missing or damaged, replace it because that's an integral part of the car's cooling system.
3) Following the instructions in the Factory Service Manual, verify that the two cooling fans are working properly.

Enjoy your new car.

 

[fatbloke-dim]

Regarding the rattle ,get under the rear end and give the spare wheel carrier a good hearty push/thump , that'll rattle like a good 'un and drive yer nuts ,'until you find it .