Aboutautohelp Expertise On hands professional expertise in all aspects of Cadillac diagnostics and repair mid 1970`s thru 2000 year vehicles. GM certified in electronic fuel injection, Automatic transmission, Heating and A/C, and onboard vehicle computer diagnostics.
Experience Held over 15 GM certifications prior to retirement in 1989.
Organizations Prior to retirement held several ASE certifications, numerous Factory certifications.
Question Hi,
I bought this 96 Deville, Northstar 4.6L @ 157K from an aution an it overheats when it warms up. I thought maybe it could be a head gasket. Appeareantly the thermostat looks to have been changed already, theres no steam coming from the tail pipe, there's no oil mix in the water reservoir and no water on the dip stick. Also it idles high when the air intake plug is in place but idles down when it's disconnected. Lastly the scanner says it needs a turbine trasmission speed sensor because it doesn't shift to 2,3 or 4 but it reverses. Where on the trans is the turbine located and is that only a dealers item. Thank you in advance.
Answer You have to split the transmission from the engine in order to replace this sensor.
As to your overheating problem, It is well known that this engine has majior problems with head gasket failures due to the steel bolts stretching out the aluminum threads in the engine block thus causing combustion chamber pressure to enter the coolant flow thus restricting the flow of engine coolant.
The fix is to pull both heads, drill outall the head bolt holes, Install steel heli0-coils and install different head bolts and add engine coolant sealant pellets to the engine coolant.
