99 Chevy Venture Mechanic just replaced cracked head. Didn't realize it was 2stroke engine. Had to redo valves. Still overheating, but not bad. Replaced gauges. Nothing changed. Mechanic stumped. Checked coolant fans myself. Only running when a/c on. Found relays over battery. Could they be probelm? Do they just pull off board and push new ones in? Also read fans may be no good. HELP!!!
Country: United StatesMake: ChevroletModel: VentureYear: 1999
Those relays do just pull out and push in so they are easily changed. If the fans are running with the AC on the fans are good, they just may not be running when the engine is getting warm, do you know what temp the engine is getting up to?
The gauge is staying above half-way mark and then will periodically go to near red and then back down. Starts off cold and rises just like it should. With air on and fans running, it still a little above half-way. Mechanic says he checked temp and not overheating, but guage only going to red whhile driving.
Fans are definitely not running unless air is on.
Do you know if the thermostat was changed?
Changed about a year ago, but that crossed my mind too. Would the relays cause the fans not run when engine getting hot? Engine still sounds like it's missing, not alot, and service engine soon light is on. Before cracked head changed, light meant 2nd cylinder not firing. Could that cause overheating as well?
I would at least try a new thermostat but there is a fan problem if they will not run with the AC off but usually when that is happening the problem is the coolant temp sensor, it may either be sending the computer the wrong temp or it may even be giving you a incorrect reading on the gauge making you think the temp is higher than it is, but the fans will not come on by themselves until the real temp reaches 226 or so. There is a possibility that the relay/relays are causing the fans to not run but its not a common problem. The misfire should not cause a over heating problem but it should be fixed because that can cause catalytic converter damage.
So where is the coolant temp sensor? Also where is thermostat now-a-days? Would you replace fan relays? Plugs replaced. Would bad wire cause missfiring?
he coolant temp sensor is in the thermostat housing on the drivers side end on the engine, the thermostat is quite difficult to change on this engine because it is below the exhaust crossover pipe. I would not change the fan relays I really do not think they are your problem, I do not even remember the last time I replaced one of these. Yes the plug wires can cause a misfire so if they have not been replaced thats a good place to start for the misfire issue.
Is there any other reason the cylider could be mis-firing?
There are many reasons for a misfire, it could be a bad new plug, bad injector, bad cylinder/low compression, bad valve, wiring issue to the injectors or coil, ect.
I was totally afraid of that answer, but thank you for giving it. You have been very patient, timely and excellent to work with. Thank you.
Thanks for asking and good luck with the repairs.
28 year experience, Master Mechanic