az0884

I was driving my car just normal driving and I began to notice it was running kind of weird and idling rough. I got on to the freeway and drove about 10 miles and then a light comes on in the dash saying check gauges. So then I notice the temp gauge is almost all the way to the right so I pulled over immediately and shut the car off. The radiator and water pump and antifreeze are about 6 weeks old so I figured ide try replacing the thermostat and see if the overheating goes away. So I replaced the thermostat and then proceeded to top off the radiator. I knew there was a bigger problem when the radiator took a whole gallon and still wasnt full. There was no coolant leaking under the car. I started the car up and white smoke began to pour out of the exhaust and it had that sweet antifreeze smell to it. My first though was that I blew a head gasket so i had the car towed home and i began to take the top of the motor apart. Once i got the intake manifold off I noticed the inside of the manifold seemed moist. There wasnt any coolant pooled up so im not sure if it was moist from coolant or if it was oil.

Does this sound like i blew a head gasket or could the intake manifold be leaking coolant into the inside of the manifold? Im definately going to replace the head gaskets regardless since ive got everything torn apart but im nervous about putting that intake back on only to have the same problem.

wrd1972

There is no coolant that passes throught the intake manifold. There is coolant that passes throught the throttle body though. The crossover point is via the steam pipe on the back side of both heads.

Sounds like a head gasket.

Stl94LT1

What does your oil look like?

az0884

The oil is still clean and full...the radiator however was near empty.

RUDEDOG

Pull the heads and see if one of the cylinders has been steam cleaned.

WS Sick

I'd say just by your disctiption that the gasket is blown between a cylinder and a waterjacket. I would look over your plugs and look for a steam cleaned plug, then do compression test, You can also refill the radiator put air with a compressor to the suspected bad cylinder and see if air comes out the radiator.

az0884

Im going to replace both head gaskets regardless and get the heads machined. I just wanted to make sure it wasnt a bad idea to put the same intake manifold back on becasue my neighbor was telling me it could be the intake. If I get the heads ported will I need to replace anyhthing else? I think ill do new valves and lifters and possibly 1.6 rockers..anything else that should be replaced? Also, I broke quite a few vaccume lines removing the intake manifold..is there any sort of kit that includes all the lines or are they all sold individually?

WS Sick

As far as I know the lines through GM are on an individual basis.

I would put some fresh springs in there and think real hard about a cam and tune

az0884

Ide really like to do the cam but it has 100k miles on it and Im nervous about doing the cam w/out new bearings and Im not about to pull the motor in my driveway. Do u think 100k is too much to do cam w/out replacing the bearings?

G. McDonald

I had the same problem when I removed my intake recently to do heads/cam, etc. I found I was less likely to break a plastic tube if I heated it a bit before trying to pull it apart, particularly if you are taking the thing apart in a cold garage (I was doing the work in an unheated garage in January). I just used a standard heat gun.

And yes, those hard plastic lines are only available from GM - get ready to be taken advantage of.

Good luck.

The Engineer

The intake manifold on an LT engine "can not" cause a coolant leak into the crankcase, or intake runners. As pointed out above in a prevous post, there "aren't any" coolant passages in the LT1 intake manifold. LTs (2nd Gens) are reverse coolant flow system engines.

WD

az0884

Taken advantage of? Now im scared. How much does the dealer charge for those hard plastic lines? The rubber ones i should be able to use whatever right?

The Engineer

The OEM (application specific) LT1 replacement plastic vacuum lines can be ordered/purchased individually at a GM parts outlet at a reasonable cost. Yes, you can also buy some generic 1/8" rubber vacuum line and make your own replacements (maybe not as neat as the OEMs).

Also, tell your neighbor about 2nd Gen LT engines and the reverse coolant flow system (dry intake).

WD

az0884

Thanks guys, youve been very helpful

FL3

I am going through the same thing. Had my check gauge light come on, automatically looked at the temp gauge, it was just about pegged. Pulled over, shut it off. Thought, just water pump. Decided to replace water pump, opti, plugs and wires. I pulled the number 7 plug and boy, was I surprised at the flow of antifreeze out of the cylinder. I have the water pump, opti and y-pipe off so far. I figure to have heads checked out and at least, new guides put in. 104 thousand on motor.