how to change head gaskets?

[deetree]

With the recent post of overheating problems, we've come to the conclusion after much talk with a few garages, owners of the 3.4 V6, who are aware of the problems with this engine, which brought us to this conclusion that the head is cracked, has anyone done this before here? Figured it is the best place to start.

[Cressidaadr]

Originally Posted by deetree

With the recent post of overheating problems, we've come to the conclusion after much talk with a few garages, owners of the 3.4 V6, who are aware of the problems with this engine, which brought us to this conclusion that the head is cracked, has anyone done this before here? Figured it is the best place to start.

I have not but a search of the forums will give you a pretty good idea what you are dealing with. What exactly makes you think of headgasket instead of something else? Tell us more history and mileage, symptoms, etc.

[dewaynep]

I agree with Cressidaadr. What makes you believe there is a head gasket problem and not just the lower intake manifold gaskets (or a leak elsewhere)? Now, if you are saying that you have allowed the engine to overheat several times, or, it got way overheated then I would say you should look into head gaskets and possibly cracked heads. Are there any combustion gasses in the coolant? Any coolant in the oil? Any visible leaks? White exhaust? How's compression on all cylinders? Etc.... If you plan on tackling this yourself there are some very good step by step directions on the web, or it may be worthwhile to get a subscription to alldata. It's not a technically challenging job, but there are a lot of parts and pieces to remember where they went, not to mention at least one specialty tool (torque wrench). Doing it yourself should take about a day or longer and save you about $500.

[deetree]

Hi, I thank you both for your interest in this post. There are bubbles in the overflow, looks like aquarium bubbles in a fishtank. When the engine overheats, the t-stat climbs to the top area 125 reading in a flash, the computer light comes on and I pulled over, turning the heat on. The van is a 2001 Montana, mil. is 117,000 kms, have had GM maintenance regularly, third owner, he had the intake done at 56,000 kms.

Never overheated before, this is our first summer with this van, we purchased it in December 2007.

Initial overheat, changed t-stat, replaced the coolant with new, but to no avail, it started doing it every odd trip, be fine one or two days and start overheating again.

Note* when we opened the rad, my husband noticed gunk stuck to rad cap, we are thinking it was rad sealant, quick fix. So now we figure we were "had" because previous owner had trouble with it.

[maxwedge]

Don't jump to head gaskets too quick, first there is a test kit that detects exhaust gases in the coolant that would confirm the issue, or this" sludge," if it is thoughout the cooling system, could block proper circulation, so check it out before pulling the engine apart.

[merc81]

I've got three of these. The sludge in the coolant could be from the LIM gasket leak--all of mine had it. It could also be the head gaskets/head cracks. Its very, very hard to tell a LIM leak from a head problem--you need to have someone do a careful leak down test where the cylinder pressures are measured with some accuracy. If its the LIM, the pressures in the cylinder should be OK.
I don't trust the combustion gases in the coolant test bit; It showed my engine to be good when in fact the heads were cracked in many places. Failure to find gases in the coolant isn't an indicator that your heads are OK, just that they aren't leaking into the coolant.
My last experience was on an engine of 165K miles. Both the LIM was leaking and the heads were bad. It was impossible to sort out what caused what symptom. Best to approach the problem as it unfolds. Buy a LIM kit ($50) and plan a day to change the LIM out. While the engine is open, do a leak down test and see if the results warrant pulling the heads off for further testing at a shop. If not, put it back together and see what you get. $50 and an afternoon's efforts aren't too much to risk should the heads be bad and the problem not be solved by the LIM replacement.

John

[Cressidaadr]

Originally Posted by merc81

My last experience was on an engine of 165K miles. Both the LIM was leaking and the heads were bad. It was impossible to sort out what caused what symptom. Best to approach the problem as it unfolds. Buy a LIM kit ($50) and plan a day to change the LIM out. While the engine is open, do a leak down test and see if the results warrant pulling the heads off for further testing at a shop. If not, put it back together and see what you get. $50 and an afternoon's efforts aren't too much to risk should the heads be bad and the problem not be solved by the LIM replacement.
John

I would say allow 3 days if it is your first time to do the LIM gaskets. I was getting coolant in the oil so I just did mine for first time and there is no way I could have done the job in 1 day. I think I could do it maybe in 2 days second time around.

John, I think you are correct about the difficulty in determining if LIM or head. Are you saying that if you are not sure if it is LIM or head problems that it isn't a bad plan to just do the LIM gasket first and wait and see how it goes? If that doesn't seem to fix the problem then go back in and attack the heads later?

Within days after I finished the LIM gasket my water pump started leaking. I think the seal went bad because or rust that developed after I had drained all the coolant and was running water for a week or two trying to get all the Dexcool out.

I am still seeing small bubbles coming up in the overflow tank with the engine running and for a minute after shutdown. (The bubbles actually go faster right after turning the engine off.) This has me concerned but I am hoping I still have air pocket in system that is working it's way out despite opening both air bleed fittings. I notice air from the rear heater is not getting warm so hopefully that lends credit to my theory for now. I was hoping to have it all sorted out and done before winter. I hate to think about having to go back and do the heads so I probably will wait it out for a while and see what happens. As someone said, "it will either get better or get worse".

[Camry93]

I recommend to anyone with a LIM leak to replace the Head gaskets as well if they plan on keeping the vehicle. Doing the HG is not much more work than the LIM as your already there. It might cost $150-350 if heads need machining then you dont have to worry about it for years. I had the LIM done at 90k then had to do the HG at 125k.