Based on this:
I shouldn't take a chance driving it the few hundred miles back to NC for that next phase of my project. Searchy reveals a few head gasket replacement threads:slimdevil27 wrote:There are several ways that a head gasket will fail and each will produce different symptoms.
First are the compression leak failures. In nearly all of these failures drivability problems such as misfiring will occur. If the head gasket fails between two cylinders you will have low compression on both cylinders, misfiring, and usually backfiring into the intake tract, which can blow off vacuum hoses and intake boots. A compression test will verify this type of failure with low/no compression on two adjacent cylinders.
The other type of compression leak is into a coolant passage or oil passage.
With a leak into a coolant passage you may or may not have coolant leaking back into the cylinder. The failure may act as a one way valve and only leak at pressures higher than what the cooling system runs at. They may also only become evident at high rpm and under load. This is the early stage before complete failure that will allow coolant back into the cylinder. This may cause misfiring, oil contamination (milkshake appearance), white smoke from the exhaust and a no start condition. The no start will happen when there is coolant in the combustion chamber and the engine tries to compress the fluid. Fluid cannot be compressed, you can only apply pressure to it. This is referred to as "hydro-lock". If this happens while driving, severe engine damage can occur. Broken piston/rings, bent rods, thrown rods, etc. If it happens when trying to start the engine, don't worry, none of this is likely to occur. With hydro-lock you will distinctly hear the solenoid click and the starter engage, the engine may turn over once before clunking to a stop. Subsequent attempts will produce very little turning of the engine, but again you will feel the starter engaging and trying to turn the engine. Stop and pull the plugs, the waterfall of coolant(or gas from a leaking injector/carb) will be readily apparent.
A compression leak to oil passage leak, on most engines, is unlikely. The reason is that most passages are on the periphery of the block with coolant passages between them and the cylinder. Some older straight 6 cylinders have pushrod passages that run close to the cylinders and these are the type that may have this type of leak.
The last type of head gasket failure is from a coolant passage to an oil passage. Since there is no loss of compression in any of the cylinders, drivability is not affected and usually the first symptom is overheating due to a low coolant level. The oil will have the typical milkshake appearance. On some types of engines this is not conclusive for a head gasket failure. In particular the Toyota 22R engines have a tendency for the timing chain to wear through the front timing cover exposing the coolant passage that feeds the water pump. This only occurs if the timing chain guide (plastic like ours) disintegrates.
An oil galley to coolant passage would pump oil into the cooling system, it's possible but I've never seen it.
For diagnostics- Determine which conditions apply. Check the oil first, that's the easiest.
Milkshake appearance of oil- Coolant to oil or coolant to cylinder. The later accompanied by white smoke from exhaust and misfiring of that cylinder.
Coolant loss from overflow-Combustion to coolant-The main symptoms to look for on this type of failure is immediate pressure in the cooling system on start up/revving. On a cold engine, with the cooling system full start the engine. Squeeze the upper radiator hose and rev the engine. If the hose starts and continues to build pressure then you most likely have a compression leak into the cooling system. This is the very beginning stage of head gasket failure. The single best way to verify this type of failure is with a block tester as mentioned. Most of these test kits are $50 or less.
http://www.amazon.com/Lisle-75500-Combu ... 789&sr=8-2
The tube is placed on the radiator cap opening and the test solution is added. With the vehicle running any compression gasses will bubble up through the test solution. If HC (hydrocarbons) are present the solution will change color, typically from blue to yellow.
If you have pressure remaining in the cooling system after it's completely cooled down, say overnight, or slimy black gunk in the overflow even without noticeable overheating you should block test it with a kit.
The more dramatic way that this presents itself is with a blown hose or blown radiator. The sudden pressure spike of combustion pressure into the cooling system finds the weakest link, the path of least resistance and promptly blows it up to let you know. It's advisable to do a block test anytime you have a ruptured hose that by appearance doesn't look bad or feel soft and squishy and definitely anytime the plastic on a radiator shatters.
Coolant loss, misfiring, white smoke- Coolant to cylinder. In the beginning stages you may notice a rough run on cold start and white smoke that dissipates. This is caused by seepage into the cylinder as the cooling system depressurizes while cooling down. As it gets worse the white smoke will be continuous. The oil may gradually become milky as the coolant leaks down past the piston rings. Pull the spark plugs and look for one that's clean. The steaming coolant does a really nice job of cleaning the combustion chamber and piston as well. That was actually how they cleaned the engine way back when. Run it at high rpm hot and dribble or spray water into the carb. Effective, but not recommended. Anytime you are losing coolant and can't immediately identify the source, and after repairs, a cooling system pressure test should be done. You may be able to rent one from the local auto parts store. On our engines you can disconnect the cooling reservoir return hose, clamp a cap to the reservoir and attach the hose to a bicycle pump, or attach it to the reservoir and securely plug the hose. Any pressure over what the radiator cap is rated for will be vented and the rest of the system will be pressurized. This is helpful for slow seepage that steams off leaving no wetness and also in and around the front of the engine. Weaving an inspection mirror in past a spinning fan and belts is not a good idea. If no external leaks are found then pull the plugs and either look in the cylinder, I use a bore scope, or roll the engine over by hand watching for spillage from the spark plug hole. 1/4 cotton rope makes an excellent dipstick to thread into each plug hole, wet a green is not good. If at first you don't succeed then let it sit pressurized for 10-20 minutes and retest.
The cylinder to cylinder blown head gasket typically presents as a rough run. Pulling the plugs will usually show which two are leaking, however a compression test will confirm this. It's a good habit, especially when doing a tuneup on a rough running engine, to do a compression test every time. With a remote starter switch this can be done in 10 minutes or less and besides the plugs are already out.
The only cracked heads that I've seen are on engines that were run after overheating and the owners just added coolant and kept on running it or they were run low quite some time. Some engines are more prone than others but it's usually neglect that precipitates cracking.
M30B35 head gasket DIY for dummies
Head Gasket M30B34
I've tried a few searches here for a M30B34 head gasket DIY thread. While I'm looking, what tips do you MyE28rs have to share about M30B34 head gasket replacement?
This motor will only be in this car temporarily. I'm going with a different motor eventually. It has high but undocumented mileage and I only want it to be dependable during the build so I can move the car to various locations within Virginia and the Carolinas. I don't want to spend much more money on the motor. I got another head with it, but haven't identified what it is (PO was planning to build and swap it into this car - he did not tell me the existing head was positively bad)
What are your thoughts on my lifting the head, replacing the gasket and then just go merrily on my way? - i.e. no machine shop cost.