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This started as a cooling issue but now im thinking its wiring. The sealant goop that GM used on the C100 bulkhead connector, is that suppose to be all over the pins? That ***** is everywhere! Im thinking its causing a short and making my gauge read high. If it is not normal and most likely the root cause then disregard the rest of this post and just tell me the easiest way to clean it. Otherwise...
82 camaro, swapped lg4 with 350, no computer, no AC, 224/230 cam @50, initial timing advance 16 degrees btdc, aluminum heads, air gap intake, 600 carb. Drove great after rebuild for 2 years in SC. Now in KS and it overheats only around cruising speeds above 60mph. I checked the air dam and no problems there. The fan clutch, with a cooled overnight engine, freespun. I was planning an electric fan swap anyways so I did that using the diagram i uploaded. Im a mechanic not an artist! I am also aware the wire the to the gauge is a power wire. The system operates fine using the over ride switch. However, my temp gauge will redline and the fan wont kick on using the temp switch. I used an IR thermometer and found the following, water neck at base 160, rad cap 90, upper hose 160, lower hose 140, coolant under cap inside the radiator 180. The outer portion of the sender corrisponds to the temp the gauge reads so im thinking the sender might be bad. It was the original off of my lg4. My gauge will drop almost instantly to well below the 220 mark after i kick on the fan manually. Using a multimeter i checked both the fan relay temp switch (210 degree switch) and gauge sender for continuity to the head and that was good from the outer part, and inner part was open. Varified good continuity from temp switch to relay. Varified both heads were grounded. Got 12vdc to the sender and 63.9 ohms to ground on the green wire. Disconnected C100 finding that someone took a taco bell crap in it and shot no shorts to ground to the green wire to temp sender. I need to pull the gauge cluster to shoot the c100 jack side to the gauge for a shorted ground but im hoping the goop all over every pin was my 63.9 ohms to ground. Im just curious how my temp gauge drops instantly when i manually flip the switch. But grounds are funny like that. Whew!...i did all that in one breath.
Last edited by Boz2882; 10-06-2015 at 08:28 PM.
Reason: stupid tablet buttons
"overheat" means different things to different people. IMO; overheating starts just before the coolant bubbles into the overflow. These cars were meant to be @ around 220 at operating temps.........
It was the original off of my lg4. My gauge will drop almost instantly to well below the 220 mark after i kick on the fan manually. Using a multimeter i checked both the fan relay temp switch (210 degree switch)
IIRC the factory fan temp switch turns on somewhere around 235 degrees.
Remember that the temps and markers ( or segments ) shown on the gauge are not equal. That's to say the middle of the gauge is not the middle of the temp range.
If you ground the green sending unit wire the gauge should peg past the red line.
In my experience the coolant temp will drop pretty quick once the an electric fan is activated.
I don't bother with an IR thermometer. IMO; THE SIMGLE MOST important test reading is taken when the coolant starts to bubble into the overflow. If I need to check the stock temp gauge I'll let the car overheat and as soon as the ( PROPER RATED ) radiator cap allows coolant into the overflow,... I check the gauge reading then shut it off. If it's reading right around 250-260 then I know the gauge is reading the way I want it too.
To check the rest of the system I simply feel the upper hose to be sure the thermostat is opening at the rated temp after cold start-up. ( Feel the upper hose get hot and then read gauge ). To check an electric fan I'll wait until the temp climbs to a little over 230 and expect the fan to kick on. ( I prefer adjustable fan relays. ) Once everything seems OK while the car is parked,... I drive it and adjust if needed.
Temp gauges are notorious for being wrong. Thee is really very little to the system. Most of the time the gauge is faulty but many times the 25+ Y/O cluster printed circuit is to blame. It's pretty cheap and easy to buy a new coolant switch and install it - that SHOULD eliminate it as a possible problem.
"overheat" means different things to different people. IMO; overheating starts just before the coolant bubbles into the overflow. These cars were meant to be @ around 220 at operating temps.........
IIRC the factory fan temp switch turns on somewhere around 235 degrees.
Remember that the temps and markers ( or segments ) shown on the gauge are not equal. That's to say the middle of the gauge is not the middle of the temp range.
If you ground the green sending unit wire the gauge should peg past the red line.
In my experience the coolant temp will drop pretty quick once the an electric fan is activated.
I don't bother with an IR thermometer. IMO; THE SIMGLE MOST important test reading is taken when the coolant starts to bubble into the overflow. If I need to check the stock temp gauge I'll let the car overheat and as soon as the ( PROPER RATED ) radiator cap allows coolant into the overflow,... I check the gauge reading then shut it off. If it's reading right around 250-260 then I know the gauge is reading the way I want it too.
To check the rest of the system I simply feel the upper hose to be sure the thermostat is opening at the rated temp after cold start-up. ( Feel the upper hose get hot and then read gauge ). To check an electric fan I'll wait until the temp climbs to a little over 230 and expect the fan to kick on. ( I prefer adjustable fan relays. ) Once everything seems OK while the car is parked,... I drive it and adjust if needed.
Temp gauges are notorious for being wrong. Thee is really very little to the system. Most of the time the gauge is faulty but many times the 25+ Y/O cluster printed circuit is to blame. It's pretty cheap and easy to buy a new coolant switch and install it - that SHOULD eliminate it as a possible problem.
Just my 2 cents !!
Your 2 cents are appreciated!
When i grounded the gauge it does peg out. I replaced the sender because sitting cool i would get 55 ohms between outer part and inner connector. The gauge no longer skyrockets after idling 5 min and when i manually turn on the fan the gauge no longer drops drastically. However, after letting the gauge climb above 220 then the thermostat opens, temp drops and the upper hose gets hot then the gauge slowly climbs back up and gets maxed in the red. I took a reading at the overflow hose and it only got to 90 degree F. The water neck temp eventually got to 210 and my fan still didnt come on automatically. Im going to get an aftermarket gauge.
10-06-2015, 07:25 PM
