I have changed the water pump, thermostat, and intake manifold gasket. compression test checks out fine. radiator is good. it will set and idol and never overheat. as soon as i start down the road the temperature gauge will start rising and will not stop. heater works until overheating starts. fans are working fine. i actually eliminated the thermistat.runs a little cooler. but still overheats when you run it hard or hold it steady on any speed. I would greatly appriciate any ideas. have been working on cars for over 10 years and never had this kind of problem.
2006-08-21 11:10:34 · 3 answers · asked by wardxjc 1 in Cars & Transportation ➔ Maintenance & Repairs
Are you SURE it is really overheating, or are you just believing the gauge.
There is a problem with G.M. here with some ground circuits from the engine to the computer and the dash warning instrument.
If the computer sees the engine temp above 240 deg F it will shut the engine down. If the PCM thinks the engine is hot, it will do all it is programmed to do like turn the fans on, turn on dash warning lights and activate a chime, and when it gets to a certain temp, it will shut the engine down to reduce engine damage caused by excessive heat.
At this point you are in need of an infra-red thermometer to compare the actual temperature with what the PCM sees and what is showing on your instrument panel.
I just checked at the ASE website, and there were a couple of these that were found to have a bad ground circuit, so tha PCM was receiving garbage for data, and it makes garbage decisions.
It appears you have done everything else right, so now it is down to doing VOLTAGE-DROPs and checking pin voltages.
BTW--Do you see any foam in the coolant, or excessive pressure in the system? Clear sign of either cracked head or block, or a bad head gasket.
Good Luck
2006-08-21 11:40:48 · answer #1 · answered by Ironhand 6 · 1⤊ 0⤋
Check for a blown head gasket. Also, I have seen some of these engines crack the block if they are run hot for any length of time. Don't trust a compression test, do a cyl. leakdown test, and if you can find someone with a block test kit ( usually around 35 dollars at a parts store) use it.
P.S. Run the engine untill it is warm, let it cool enough so it is SAFE !! to remove the cap from the cooling system and check for a burning trash smell. These engines smell awfull if they blow a head gasket.
2006-08-21 17:18:34 · answer #2 · answered by B H 3 · 0⤊ 0⤋
have you checked the compression of your cylinders?
blown head gasket or a cracked head will do this to you too
2006-08-21 11:17:08 · answer #3 · answered by Anonymous · 0⤊ 0⤋