I just hit 105k miles on my 3.1 monte LS, when i first got it, it had 99k miles and needed a water pump. Changed that out no problem. Got to around 102k miles, changed the plugs with ac delco platinum and ac delco premium plugs. Then not to longer down the road changed the oil with gtx high mileage oil, and made my own cold air intake for bout 60 buxs from spectre. Well i changed the thermostat yesterday and filled it up the radiator and expansion chamber, well the coolant started to disappear, and i thought i had a leak, well i checked my oil today, and low and behold i had a milky oil mix. My question is how hard is it to replace a head gasket??

 

this is for the 3400 but its the same engine basically so it will be virtually the same, doesnt seem to be too difficult just the rods are something to be careful about

http://d-tips.com/general/articles/article.aspx?id=2

 

Certainly doable just pace yourself and torque accurately. Install new head bolts (torque to yield). I bought a 99' w/94k & ended up doing both shortly there after. Plan on just doing both but very difficult to get the pushrods on rear head into correct orientation-use a mirror for visual aid. I also changed over to green coolant at that time

 

i wanted to do dexcool, i prob will after i fix the head gasket, cuz i gotta flush the system. What is your guys opinion on the dexcool??? The only problem is i dont have torque wrenches. So this is probably gunna a good challenge for me

 

get a 3/8 torque wrench at Harbor freight

 

Chances are better that lower intake manifold gaskets have gone bad. They are notorious on these engines. Do a compression check on all the cylinders before you go any farther. LIM gaskets arent a bad job at all to do. Alot easier than pulling the heads off.

 

I always replace both sides and lap the valves while it's open. Replace any other gasket or seal you can afford. It won't get any easier. I'd rather spend a little extra and not have to go back to say change a valve cover gasket or exhaust header gasket.

 

Yeah, it's probably your LIM gaskets going bad, but while you're down there you might as well do the head gaskets too. Shouldn't be too hard, OHV motors are easy to work on.

 

I'm not sure that I'd agree with the suggestions to pull cylinder heads, lap valves, and replace exhaust manifold gaskets as a part of a lower intake manifold repair. That's a lot of extra work, and as far as I know, there's no issue on the 3.1's where head gaskets or exhaust gaskets are going bad. I'd replace any gaskets that are removed as a part of the LIM repair, but that's it.

I had to replace the LIM on my Lumina at 153,000 miles. It's now got 203,000 miles - so far so good.

 

head gaskets on the 3.1's are common and since doing the work it's better to just "mentally bite the bullet" and get 'er done!
When we got our ls w/94k I figured LIM but turned out to be the left(front) was seeping...I did both & found getting the valve train installed on the rear a real PITA! I also changed waterpump & thermostat while there-cheap enough. I did use GM gaskets but aftermarket pump & stat. Been excellent for 2-3 years now! now if I could get that RR qtr panel closed up!
If you're near an Advanced Auto, buy your parts online and use instore p/u Big40(40.off100.)Big30 etc.etc. A123 is another...