Has anyone done a head gasket replacement?

[TwoUpTourer]

In my VZ I have air/gas blowing from the cylinder into the coolant, forcing it into the overflow.

Likely culprit is the head gasket, not sure which side yet. Has anyone tackled this job before?
I have pretty much all the tools to do, and whilst not particularly enthusiastic to do it, financially no choice.

 

[hotrod]

what about manifold gaskets , they are common problem , if you start doing the head gasket you have to machine the block to , if it was the head u think u have water in the oil. i be getting the proper check up first to verified it

 

[TwoUpTourer]

what about manifold gaskets , they are common problem , if you start doing the head gasket you have to machine the block to , if it was the head u think u have water in the oil. i be getting the proper check up first to verified it

I had a mechanic look at it, did a sniffer test to to see if carbon monoxide was bubbling up in the coolant, but the problem is that the gas only pumps in under high pressure of the combustion chamber, particularly under load such as driving up a hill, which I do all the time. I don't think there is sufficient pressure in the exhaust side to blow through.
Heads I'd get planed, but the block I'll pass up. Pain in the neck really. I'm going to get a leak down test to determine which cylinder is guilty.

 

[99notout]

In my VZ I have air/gas blowing from the cylinder into the coolant, forcing it into the overflow.

Likely culprit is the head gasket, not sure which side yet. Has anyone tackled this job before?
I have pretty much all the tools to do, and whilst not particularly enthusiastic to do it, financially no choice.

Are you really sure it is a head gasket? have you done a leak down test? A simple and easy what to test for combustion gasses in the coolant is to put a balloon over where the cap goes, or a plastic bag and rubber band, if you really do have a gasses entering the cooling system the ballon or bag will inflate pretty quickly. Do it on a cold engine though.

I bet you have an air leak in the cooling system and it is sucking in the air somewhere else. Go and have the cooling system pressure tested...

 

[adamcawood]

The radiator cap is know to stuff up Have you changed the radiator cap ? The balloon or bag trick is good aswell

 

[DeanoV6]

I bet you have an air leak in the cooling system and it is sucking in the air somewhere else. Go and have the cooling system pressure tested...

+1 as he said

 

[TwoUpTourer]

+1 as he said

The problem I have with that is that the coolant system operates under a reasonable amount of pressure, so the only way air/gas can enter it is if where it is coming from has an even higher pressure. There can't be much sucking going on.

This to me leaves only the combustion chamber, which means either a gasket weakness or porosity in the head.

The balloon/rubber band is a great idea, and I will try it this weekend. I had a mechanic with a sniffer, but there was too little bubbling up at idle for it to register. I believe there is a similar type of sniffer that operates pretty much on the balloon principle, whereby it collects a pile of gas over time to the point that the liquid in the sniffer can change colour, or not as the case may be.

 

[99notout]

I still reckon it is air getting in elsewhere. Head gaskets are pretty uncommon on these, unless you have boiled it dry?? Go and get a radiator shop to check it is holding pressure and I bet you will locate a leak somewhere, and not into the combustion chamber. Look for the common faults first, then look at the hard ones mate, don't go straight for porosity or head gasket yet, but it is your money so go your hardest, but why??

 

[DeanoV6]

The problem I have with that is that the coolant system operates under a reasonable amount of pressure, so the only way air/gas can enter it is if where it is coming from has an even higher pressure. There can't be much sucking going on.

This to me leaves only the combustion chamber, which means either a gasket weakness or porosity in the head.

The balloon/rubber band is a great idea, and I will try it this weekend. I had a mechanic with a sniffer, but there was too little bubbling up at idle for it to register. I believe there is a similar type of sniffer that operates pretty much on the balloon principle, whereby it collects a pile of gas over time to the point that the liquid in the sniffer can change colour, or not as the case may be.

Coolant under pressure expands and goes into overflow tank or leaks. When it cools it draws in air because it is easier than sucking it out of overflow tank back into motor or coolant tank is empty. could be something simple like radiator cap or pipe to overflow tank needs a cable tie around where it joins to radiator cap housing (sucking in air) if coolant is leaking it could be from a split in radiator tank that opens up under pressure, water pump, seals where alloy radiator pipe goes into the block, thermostat housing at the rear of the motor (look for dry red coolant on the bell housing) heater tap. it will be leaking from some where and replacing it with air,
I was in thinking Head-gasket with mine, but would fix a leak and another would appear finally got on top of them and have had no problems with it for 2 years.

I Think there is a die that you can put into coolant to tell you if exhaust gases are present. I would get a really good high pressure long time cooling system test. check and top up coolant daily so you can see whats going on.

 

[TwoUpTourer]

thanks for your responses guys, they are all helpful.

I'm not getting any leakage from anywhere, it 100% ends up in the overflow bottle. Regarding sucking in air when it cools down, I understand the point, but by the time it gets to cooling down it is already over red rover. From cold, the system when it is entirely full, radiator bleed valve bled so the radiator is full to overflowing, it all warms up, and air/gas is forced into the coolant, pushing it out into the overflow bottle.

It is definitely happening at the hot stage, not afterwards, and there is not a drop dribbling out anywhere it shouldn't be. In fact when I siphon it out of the overflow tank and then top up/bleed the system, I'm back where I started, everything full to where they are meant to be. There is no overall loss of coolant. This is why I think something is forcing air/gas into the coolant under pressure.

I went and saw a radiator guy yesterday, and he also had the standard hand held sniffer that changes colour in the presence of carbon monoxide. Problem is that the car really has to be under load for there to be sufficient pressure to pump lots of air/gas into the coolant. Idling produces so little that the hand held sniffers don't pick it up. I live in the Adelaide Hills(SA) so I'm up and down hills every time I drive.

He has pointed me to another radiator guy who has a $20k testing machine, including carbon monoxide, so that is my next step.

I agree with the comment that head gaskets are generally not a problem in a VZ, particularly one that has just done 140k. But.... my first mechanic rang a mate of his from a Holden dealership, who said he was doing 2~3 head jobs a month on VZs because of this problem.
Anyway I did learn one very interesting piece of trivia that explains what insane person would ever place a thermostat behind the engine in an impossible spot. Turns out GM bought the engine design from SAAB (remember them?) where it was intended to be an east-west motor, and where the thermostat could be accessed in 10 minutes. GM turned it north-south.