3.4 issues - intake or head gasket?

[mtnpat]

Please help me diagnose whether I have a bad intake or head gasket on my 2000 Impala - 3.4 engine. Here are symptoms:

(Note: motor has 138,000 miles on it)

1) Have never had any overheating issues, then one day the water temp gauge went from normal operating range to red lined in about 20 seconds, motor shutdown to minimum power via the overheating protection system, pulled car over within 1/4 mile. Towed car home. Replaced thermostat, using my old school brain thought it had stuck shut. Flushed and filled colling system.

2) On test drives got erratic temp gauge readings. Could not get all air bled out of cooling system. Every time I bled the air out, it returned.

3) Stopped driving car, but noticed a "miss" when sitting idle, you would hear it from the tail pipe, some white smoke from tail pipe also.

4) Some white residue under oil fill cap and PCV valve. No visible water contamination in oil when drained.

Anyone have an idea as to whether this is a blown intake or head gasket?

Thanks in advance.

[3.4imp]

I think you definately have a intake manifold gasket problem. you should've replace thermo switch while u were doing thermostat. you may also have a catalytic conv. problem also. might sound crazy but they go out very easy on these impala's. gotta luv how gm & it's employee's stonewall us stupid folk. I'm too dumb to put 2&2 together. there's a special place in HELL for gm & its associates.

[p-impala]

my head gasket went on my 01 at 89,000km and the mechanic said that whoever put it together over tourqed the bolt. there was no corrosion.

[ghostrider1]

The problem with Dexcool is that when it is combined with air it becomes acidic, therefore causing the problems with the gaskets. One solution is to have a pressurized overflow coolant bottle, like on the full size trucks and to have the system bled. If you notice all the problems of "coolant mud" and leaking gaskets are mostly all cars, not the trucks.
Of course the other solution, is to drain the Dexcool and use the green antifreeze. Just make sure the dealer doesn't find out.

[hennigm4]

My sorry 3.4 engine did the same thing, Itraded it in before it went completly 104K on it. I am very sure it was the head gasket. Is that what it was wit yours?