My 1990 gmc sierra 1500 temp. guage stuck after new thermostat.

no, your coolant sensor is next to your thermostat, replace it and your thermostat also. don't think you have a level sensor !!!!! do you ? this is a GMC, not a BMW. after repair, clear code from computer.

your thermostat is designed to open at a specific temp, for example a 195 thermostat is supposed to start opening at 195 but will not fully open until it reached about 210. Your ECM has determined that your thermostat is not 'closed', but is hung open, not allowing the engine to reach a temp that the computer is set to see. So the thermostat is either malfunctioning, or your temperature sender unit is reporting the wrong thing to the ECU. Probably a good time to replace the thermostat, if the condition persists, replace the sender unit-both items together will cost less than $30 total.

BEST THING TO DO IS REMOVE THERMOSTAT AND REPLACE, IT MOST LIKELY IS STUCK OPEN. THANKS MOTOR62500.

It depends on what reason you want the vehicle to reach 160 degrees. It seems 160 would be high to run a vehicle at. Nevertheless, if the mixture of anti-freeze and water at the correct mixture. If the mixture is not correct and it is more water than anti-freeze this will effect the heating temperature of the coolant.

http://realfixesrealfast.com/realfixesrealfast.com/Heat_%26_Air/Pages/Chevy_PU_A_C_blow_hot.html

This may be your problem. The blend door may not be opening.

Hi there,

Firstly - DO NOT run engine, when guage reads hot, as this will cause costly damage to head gasket & alloy engine head.

The fact that guage takes 1min to read HOT, would confirm the guage IS working properly.

So, other components which are likely to cause hot readings (in this order) are:

- lack of coolant (or leakage somewhere): is there sufficient green coolant at the correct level? Top up mixture to correct level. Repair any leaks.

- collapsed radiator hose: when engine is cold, start engine, then quickly watch both upper & lower radiator hoses to see if either begins to flex inwards (collapse). Replace if either hose is collapsed.

- bad/incorrect thermostat rating : when replacing thermostats, you must ensure it is of the SAME temp rating (they all differ).

- Incorrect Temp sensor rating: the ratings of this sensor must be within manufacturer's spec's.

- bad waterpump: the engine relies on the waterpump to distribute the coolant throughout the entire system. If waterpump is faulty, coolant will not flow quick enough, causing overheating.

If you still believe all of the above components are OK, then have your cooling system "pressure tested". This test should be done, before looking further at other electrical components.

Cheers,

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Bad IPC.......If u can round up a tech 2 scanner, do a guage sweep and i bet u will see the temp guage will not operate correctly......a new IPC (Instrument Panel Cluster) is really the only fix. Once installed it has to be programmed. If u need any help send me a return message.

Check coolant level. Check for heat at the heater hose going from water pump to heater core at firewall. Check to see that cable is moving coolant control valve from the closed to open position. Low mileage so it shouldn't be plugged heater core.

Sounds like there may be an air pocket in the system.
Try 'burping' the system. If this still doesn't fix the problem, check the temperature of the heater core hoses (in and out) The inlet should be fairly cool, the other should be piping hot. If they're both cold; the heater core has an internal blockage.

Next, replace the thermostat with a winter (180-195 F) derivative.
Bleed the system accordingly, and keep me posted!

The problem could be a plugged cat convertor, or fuel filter