i suggest you get a repair book.it is not easy
You need to replace your intake manifold gasket. Chevy had a bad problem with these gaskets.
I myself have had very good luck with k-seal in the past. That being said, there is no such thing as a "mechanic in a can". It might fix the problem for a while, but the best thing to do is replace the gaskets as the new intake set has updated gaskets.
In the intake manifold near the thermostat.
Seals manifold to block. metal-metal usually not airtight seal so gaskets used between surfaces.
Check to see if there is coolant on the engine block. It is common for the Monte Carlos, along with other GM cars equipped with the 3400 V6 engine to experience leaking intake manifold gaskets. A leaking intake manifold will cause oil to leak into the coolant system and even worse, for coolant to leak into the oil system.
Pull your carb and see if there is oil in the intake, if so you will need to put new intake gaskets on. If they new try tightening the intake first. Were the heads milled?Jake
i've changed many lower intake gaskets on that motor.
Look where the thermostat is attached to the intake manifold
The temperature sensor is located on the driver's side under the radiator hose, on top of the intake manifold.
The Manifold Absolute Pressure (MAP) sensor is located on the firewall side of the upper intake manifold plenum
im having the same problem with my 99. i know the V6 engines have problems with the intake manifold gaskets. only problem is my leak is coming from somewhere by the reservoir as well. check the gaskets and see if it is leaking around them. if not...hop on the troubleshoot train that I've gotten onto. good luck bro, they are great cars. i love mine.
Sounds like a head gasket might be going out. You will get more answers if you ask the same question for the engine in the car instead of the car. If it is a 5.7 liter, this is a common problem for '90's 350's. The intake manifold gaskets are defective and coolant leaks into the lifter galley down into the pan. You can do a compression check, but, unless the engine has experienced a bad overheating scenario, the head gaskets in GM small blocks don't just go bad by themselves. It's a great, legendary engine that has been screwed up by bean counters trying to save a little money on intake manifold gaskets.