Need Help With Temp Gauge Problem

[Flat Broke]

my 99 2dr 4x4 just started showing very erratic readings on the temp gauge. Today on my way to lunch, the gauge got up to 240+ but there were no other signs of overheating. I got home from work, swapped out the T stat thinking that maybe it stuck. The problem still exists. The temp gauge will move from 190-195 (where it always used to stay) to 220, then sometimes come down to 180, then jump back up to 240. The movement of the needle is smooth, and it takes about 5 seconds to go from 190-240. It will do this whether it is idling, running down the freeway, or cruising at 40. Air temps today were in the 70s.

Any suggestions would be greatly appreciated as I don't want to drop the coin to have the dealer take a peek.

Thanks,
Chris

[95tahoe4x4]

Did you switch out the temp sensor? how about the coolant, if it has not been changed out it can "build up" on the sensor causing it to not read correctly. You might just have to face that the dash gauge is bad too, why a dealer? Take it to a Napa or Carquest authorized shop.

[luvmy99tahoe]

I had that exact same problem with mine. i looked at the coolant and could not see the top. I have my oil changed every 2500 mi at the dealership and they havent been checking the coolant like they said. My last radiator flush wash supposedly 48,000mi ago but when another shop flushed it they said it was all thick. They did a reverse power flush and the temp gauge problem went away. Its dexcool at its best. I found a hirline crack in my radiator later on however and am looking for a cheap way to fix it temporaraly until I can get a new radiator. Any suggestions?

[Flat Broke]

Originally Posted by luvmy99tahoe

I had that exact same problem with mine. i looked at the coolant and could not see the top. I have my oil changed every 2500 mi at the dealership and they havent been checking the coolant like they said. My last radiator flush wash supposedly 48,000mi ago but when another shop flushed it they said it was all thick. They did a reverse power flush and the temp gauge problem went away. Its dexcool at its best. I found a hirline crack in my radiator later on however and am looking for a cheap way to fix it temporaraly until I can get a new radiator. Any suggestions?

You might try JB welding the crack in the radiator. Drain it, dry the crack, apply the JB weld and go from there. I don't think radiator stop leak will work if the crack is on the plastic tank.

THanks for your input on my problem. I went and looked and sure enough low coolant in the radiator. The resevoir was up, but the radiator was low. Probably passing an air bubble around causing the inaccurate readings. Also time for a flush on the Tahoe anyways, so it looks like I know where I'll be after work.

Thanks again for your responses.

Chris

[bigjul45]

I had this problem come to find out it was my water pump my gauge was going crazy check your water pump

Originally Posted by Flat Broke

my 99 2dr 4x4 just started showing very erratic readings on the temp gauge. Today on my way to lunch, the gauge got up to 240+ but there were no other signs of overheating. I got home from work, swapped out the T stat thinking that maybe it stuck. The problem still exists. The temp gauge will move from 190-195 (where it always used to stay) to 220, then sometimes come down to 180, then jump back up to 240. The movement of the needle is smooth, and it takes about 5 seconds to go from 190-240. It will do this whether it is idling, running down the freeway, or cruising at 40. Air temps today were in the 70s.

Any suggestions would be greatly appreciated as I don't want to drop the coin to have the dealer take a peek.

Thanks,
Chris

[bigjul45]

Check ebay for a new radiator type in tahoe radiator you will find them for about $210-$220 a lot cheaper than any body can offer also make sure your water pump is not gone

Originally Posted by luvmy99tahoe

I had that exact same problem with mine. i looked at the coolant and could not see the top. I have my oil changed every 2500 mi at the dealership and they havent been checking the coolant like they said. My last radiator flush wash supposedly 48,000mi ago but when another shop flushed it they said it was all thick. They did a reverse power flush and the temp gauge problem went away. Its dexcool at its best. I found a hirline crack in my radiator later on however and am looking for a cheap way to fix it temporaraly until I can get a new radiator. Any suggestions?

[QaloSS]

Im new but I had a 95 Impala SS that had basically the same engine, the LT1. A few of the key problems which MAY relate to the 350 Vortec Tahoes are:

Of course, the coolant, Dexcool isnt all its cracked up to be but it is a good coolant, just dont mix it with anythign else or expose it to air, such as a leak, or it will thicken up. Also, in the production of the 94-96 IMpalas, GM would include dye pellets into the coolant to detect leaks, but the pellets had a tendency to cause the heater core to clog, A FULL flush would clean it all out.

Next are the guages, there are two guages for the SS, I havent looked close enough at the Tahoe yet but the LT1 is reverse cooled and the water pump is ran off the cam so keep that in mind. There were 2 temp sensors; one was in the water pump that gave the ECM the temp readings, and the other was mounted in the passengers side of the block which sent readings to the guage in the dash.

So if your guage is messing up, there may be another sensor that is causing the problem, if the Tahoe has more than one. Just thought I would add a little tidbit of info.

Later