Hey guys,
well we went for a run today with couple of the Datto boys, and the old sedan got hot, well actually almost all the way up to H and that was mostly cruising along at 80km.
We discussed it and rekon its the head gasket, cos theres a fair amount of bubbles in the coolant, but there is no oil or milkiness.
Also could maybe just need the head to be re-torqued, cos it is a fairly fresh a15.
Could be anything guys, just wanna ask here if anyone has much of an idea before i start ripping apart the head.
Also needs topping up a fair bit when we stop driving if that matters at all.

Cheers Benny

try retorquing it, you usually need to after a run in.

Cavity/air-pocket in the system. That's what I had anyway - same symptoms.

Yeah thats what i thought originally, but why would it be heaps bubbly Chris?
Thinking about just re-torquing it and see how it goes, then if it doesn't fix it i might slap a gasket in it.

The water is low to start with, then slowly rises to the top of the cap, then when its turned off the water drops back down.

Could it be something to do with the radiator + cap setup?

My guess would be the head gasket; I had the same issue, the car ran warm and would use about a about a liter of water per two sessions (about 60-70 miles). I really didn't have any bubbles at idle but when I finally let the car warm up with the radiator cap off, the water level started rising. I finally had a friend watch while I held the motor at 4K.............that got it surging nicely and confirmed what we suspected. When I pulled the head you could see a tiny line from the water jacket to the #2 cylinder where the water was being sucked into the cylinder. Just enough to make the car run warm. Took all of an hour to install a new gasket. (I pulled the head with the manifolds attached).

Tom

This is way late Benny but here goes.

If there were alot of bubbles in the coolant from what you think is a faulty head gasket leaking into the system on the compression stroke then I would think you get a distinct smell of exhaust fumes/fuel in the coolant.

I still think it was a cavity with perhaps a problem with the head gasket as well (seeing as you need to top it up).

These air pockets can be very stubborn. what I normally do is top the system up to what looks like a full system, before this I test the thermostat in boiling water on the stove top (you'll see it open almost straight away and it should open quite a bit more than you'd expect) I then get the engine warmed up watching when the water begins to flow across the opening in the radiator. I then cap the radiator and run the engine some more and give it a good rev, I then turn the motor off and you'll here a distinct 'glug,glug' noise as the water either pushes the air out into the highest point (radiator top tank) or the air pocket settles back to where it was. I generally repeat this until I finally see the coolant level drop again, which means the air pocket has released, finally I top it all up again and give it a good run, at the end of the run I check once again that the coolant level is good and I top up if required.

It sounds like you had a stubborn air pocket in there the trick is to pressurize the system after it has warmed up, meaning you leave the cap off until the t-stat opens and then cap it to let the pressure build and then open it up again later to release what was left and or to top up again.

Sorry to hear it (the engine) burnt out. If you were in SA I'd insist you drag it down to me for a quick look-see.

But if it was a faulty head gasket, would this mean it was sold to you like that?

Also when I was running my A10 last summer it was getting mighty,mighty hot. Gylezy kindly flushed the radiator for me before the A12 transplant and he said it was absolutely chockers with what looked like stop-leak (coagulated clumps of brown shyte). Anyway if you read between the lines the best way to find out if you're a little unsure is to eradicate all the other possibilities.

It's possibly the head gasket - there's plenty of times they'll blow between a fire ring (the part of the gasket that goes directly around the top of each cylinder bore) and a water jacket. Then there'll be no oil in the water, but bubbles as you describe.

When you rev the car up, the coolant level should actually drop a touch (as the pump pushes it against a closed or semi closed thermostat and raises coolant pressure between water pump and thermostat housing - basically inside the whole engine itself.

If it had a completely blocked thermostat, then it'd heat up but the rad would be cold-ish. THen if you stopped, the water would turn to steam in pockets in the block, and backflow out the bottom hose and eventually push past the rad cap/overflow. So it isn't that.

But in your case, you are getting slight pockets of steam (or just combustion by products) pushing through from the blown gasket from the cylinder which will then push the water level up in the rad sort of thing - so that definitely sounds more like it.

There's a couple of fairly easy checks. One would be to look at the plugs - often a blown head gasket will seep water back into the chamber and there'll be some rust n the plug electrode area. Another sign is that after you shut it off, this coolant seeps into the cylinder, then when you try and start it the next morning, it struggles initially (as there's enough water in the cylinder to make the remaining air more tightly compressed (but not enough water to hydraulically lock the engine altogether)/. So the starter struggles for 2-3 revolutions of the engine, then seems like somebody doubled the current going to the starter and it spins the engine at proper startup speeds and it fires into life.

Another thing you can try if the plug test is inconclusive is to make a fitting with an old spark plug so you can pump air from an air compressor into the cylinder. Then with plugs removed, put it in each cylinder's spark plug hole, wind it to TDC for that cylinder, just at the end of its compression stroke, put it in gear (to hold it at that position) and pump 100psi in there (quite safe to do, combustion pressures are way higher) and with the radiator cap off, look for bubbling. If there are, it is the gasket - the motor isn't running so no way are the bubbles from cavitation of the water pump or anything.

If you don't have access to that, you could alternately make a quick and nasty fitting, and remove all spark plugs, and this time park the car facing uphill, and fill the radiator, then put the homemade cap on with a fitting to connect a cheap cigarette lighter tyre pump to it, and start it up to pressurise the radiator (don't let it go above 20psi, but keep it doing that for some time, shutting down, then restarting. Eventually you'll see water seeping out of the spark plug hole on the cylinder where the head gasket is stuffed (possibly more than one)

Now having said all that - definitely try re-torquing the head. Just do it one bolt at a time, loosen 1/4 turn then retension to the original final tension.

I'd also probably suggest (esp if the leak was only minor) trying 'chemi-weld'. It's the stuff that is usually run through a motor if it has had to be sleeved, as a final effort to ensure sealing the cooling system. be warned the stuff isn't magical, but it can work (I'd go as far as to suggest that if you _do_ try it, to put an old stuffed radiator on there to do it, as it can slightly clog rad cores) I have seen motors go on to do over 50,000km with one treatment of chemiweld. It's worth a look for a daily driver or a car you don't wish to spend millions on.

If it is a more serious project, then I'd go the opposite way and say you're better off pulling the head and getting it crack tested and checked for straightness, then getting it repaired/machined if and to the extent necessary, and fitting a new head gasket.

One thing - don't be tempted to go overboard on the tension - too much tension can start to damage or deform the head and be worse than not enough tension.

Thanks guys, don't have time this morning have to head to work but will be reading this tonight. Ive sorta replied at this stage in my build.