Engine overheating??? temp guage malfuntion?
(2010-11-19 15:10:05) 1. Says: Just had a shadetree mechanic do an engine swap (used motor) for me in my 90 chev p/u with a 350. it has the temp sender on the driver's side just above the spark plugs. it shows to be overheating while the sender is pluged in but you can unhook it and it doesn't..... was told by the mechanic to replace the sender and I did and it does the same thing....... any suggestions???2. Says: To test the gauge/wiring to gauge:Disconnect wire to temp sending unit (thats what it is, a switch is for idiot lights, a temp sensor is for the ECM) with key on, engine off.
Watch gauge and see what happens. It should IMMEDIATELY "peg" to either the hot or cold side (doesn't matter which) side.
Ground that wire to the frame or block, whatever is available. Gauge should peg to the opposite side of gauge than the above test with the wire unhooked.
If it fails either test, the gauge and/or wiring to the gauge is screwed up.
If it passes both tests, something is wrong with the sending unit. There should be no teflon tape on it, and the one you purchased should have been for YOUR vehicle, not the one the motor came from. Not likely to be an issue, as the only thing that changed for the temp sender was the thread diameter/hole in the head it threads into, but with parts stores, you never really can be sure they didn't give you a temp switch.
Realize your gauge is the ONLY indication you will have (instrument wise) in regards to overheating. The ECM temp sensor is not going to do anything to tell you there is a problem.3. Says: The sender probably is okay. You probably do have a heating problem. It might be as simple as not having enough water or anti freeze in the engine. Sometimes, when refilling an empty engine with coolant, it looks like it is full, but it has a lot of air trapped inside. So later on, the air is worked out, but now the coolant level is low, and not enough to keep the engine cool.
Just one thing to check.
Being a bit out of time, mainly spark advanced to much, will also cause it to heat up a bit.4. Says: Well, you have three major players in the cooling system, water pump, thermostat, & the radiator. You can remove the thermostat & run the engine without bothering the engine any, so do that first. If nothing changes, run the engine without the 'stat & with the radiator cap off. If the water pump is working, you'll see the water in the filler neck churn, and if you stick your finger in there, you'll feel the water warm-up.5. Says: If your engine is overheating the radiator overflow tank will be boiling and gurgling after you shut the engine off., plus you will hear pinging in your engine....a sure sign the engine is overheating! If not you can either further diagnose the problem with the electrical sensors or install a mechanical gauge which I prefer.6. Says: theres two sensors
one is call temp switch and the other one is call temp sensor
the switch is the one with only one wire conected to it
the sensor has a regular two wire conector
usually the one with only one wire is the one that sends the temp to the gauge
your engine may not be overheating, what it may be happening is that one of those sensors is giving a bad reading of the temp Tag: Engine overheating??? temp guage malfuntion?