Figured I would do a quick write up on this as my fix worked, but not sure why…
So 93 Sierra 5.7, temp gauge would move up to the first line but never went past. I had just rebuilt the cooling system so I thought for sure the mechanicals were all good. I pulled the coolant temp sensor on the driver’s side of the block and grounded the wires. Gauge pegged out hot, so gauge and wiring were good.
Ordered a new temp sensor without realizing there are two different ones, sure enough I got the wrong one. That said, the old one looked good when I pulled it so I just put it back and hoped I would get by without needing to order the other.
That leaves the thermostat. Not actually all that old considering the recent rebuild but whatever, I’ll try it. Lots of issues with new thermostats being bad nowadays so maybe it failed in the open position. Open it up and the thermostat was closed, so my failed open theory was wrong. Oh well, I have a new one that I just boil tested so I’ll drop it in since I’m here. Drained as much of the brown coolant out as would come out of the radiator drain (2gal) and refilled.
Bolted it back together and it worked. Temp gauge is going up to normal operating temps, did a few hard pulls and everything and temp stayed where it should. Old thermostat was closed when I took it out so it didn’t fail open, but I never had any overheating issues so it wasn’t stuck closed either…..I have no idea why replacing it worked but it did. Just figured I would throw this out there incase it helps someone else.
So 93 Sierra 5.7, temp gauge would move up to the first line but never went past. I had just rebuilt the cooling system so I thought for sure the mechanicals were all good. I pulled the coolant temp sensor on the driver’s side of the block and grounded the wires. Gauge pegged out hot, so gauge and wiring were good.
Ordered a new temp sensor without realizing there are two different ones, sure enough I got the wrong one. That said, the old one looked good when I pulled it so I just put it back and hoped I would get by without needing to order the other.
That leaves the thermostat. Not actually all that old considering the recent rebuild but whatever, I’ll try it. Lots of issues with new thermostats being bad nowadays so maybe it failed in the open position. Open it up and the thermostat was closed, so my failed open theory was wrong. Oh well, I have a new one that I just boil tested so I’ll drop it in since I’m here. Drained as much of the brown coolant out as would come out of the radiator drain (2gal) and refilled.
Bolted it back together and it worked. Temp gauge is going up to normal operating temps, did a few hard pulls and everything and temp stayed where it should. Old thermostat was closed when I took it out so it didn’t fail open, but I never had any overheating issues so it wasn’t stuck closed either…..I have no idea why replacing it worked but it did. Just figured I would throw this out there incase it helps someone else.
