Hey everybody, I've got what I hope is a simple question.. So I'm doing a leak down test on my 87 Sammy. I know I need to find TDC on the compression stroke of the cylinder. The problem is I can't figure out how to manually turn the crankshaft. I know you can put a socket on the crankshaft bolt and turn it but the way the engine is situated, the radiator is in the way and I cant fit a socket/wrench in there... but I can't remove the radiator cause that would defeat the purpose of the leak down test. I'm new to all of this but trying to learn.. Thanks for any advice!

Greg

More out of curiosity than anything else - why would removing the radiator defeat the purpose of the leak down test?

You can turn the engine by putting the car in gear and pushing it.

Well the reason I'm doing a leak down test is to test for a blown head gasket and/or find why I have oil and coolant mixing. So if I were to removed the radiator then I wouldn't be able to see if air comes out of the cap when I hook up compressed air to it.

I don't think that will work, it needs to be pretty precise for TDC and I don't think I could achieve that. From all the videos I've watched they all just use a socket on the crank shaft bolt and turn it no problem. I just can't seem to access the bolt...

Update: I ended up unbolting the radiator, while keeping all the hoses, etc. attached, and was able to weasel my socket in so I could rotate the crank shaft. Got cylinder 1 positioned to TDC and will try to run the leak down test tomorrow.

I don't see/think a leakdown test is going to be much help if/when you're already seeing coolant/oil cross contamination - and for what it's worth, I have turned many an engine to TDC by bumping the car with it in gear

Why do you think a leak down test won't be useful? I thought the point was to help locate the source of a leak. So, for instance, if I have a blown head gasket then I would be able to see the leaking compression and the compressed air would ultimately produce bubbling from the radiator cap. Am I going about this the wrong way?

I did do a regular compression test and found that my compression was relatively consistent across all four cylinders. I was surprised which led me to try a leak down test.

Also, that it good to know about pushing a vehicle to get TDC. I'll definitely keep idea that in my back pocket.

I tell you what - do the leak down test and tell me if the results help you pinpoint the leak - I'm curious as to whether or not it will actually help.

Now - this is just the way I see it - but - if you're having oil/coolant contamination, you already have a good idea where the leak is, especially if the contamination is showing up in the cooling system.  On a G13 engine, it's 99% probability head gasket, 1% probability intake - my guess is you're looking for confirmation, which you don't really need - you're going to be taking the head off.

In my mind the diagnostic information that a leak down test provides can be gotten from other tests that require less equipment & setup.

Alright, so I ran the leak down test and now I'm thoroughly confused..

When I hooked up the air it didn't show much leakage. I could hear some air from the oil cap which would indicate worn rings. I have good compression so I'm not too concerned about the air coming from the oil cap, (at least at the moment. One thing at a time!) What I expected to find was air coming from the radiator which would tell me there's a blown head gasket or cracked head or block. But I didn't get any air coming from the radiator.. But I'm leaking coolant and I have coolant in the oil. My only thought is that maybe its an issue with the intake manifold/intake gasket?

I'm not sure what to try next. I would love some advice! I was expecting a head gasket but now I'm not sure. Is there a way to test if an intake manifold has an internal leak?

Thanks again for all the help.

As I'm sure you've noticed, the water outlet elbow attaches to the intake manifold, so coolant flows through the manifold, entering where the manifold attaches to the head and out via the thermostat - I believe there is also a "bypass" in the carburettor area so tha tthere are two "interfaces" for potential contamination.

Having pointed that out - as I mentioned before - the probability of your problem being the head gasket is extremely high - what are your options - removal & replacement of the carb & intake to replace the gaskets, and if that doesn't resolve it, removal of the carb & intake a second time, as a part of the removal of the head to replace the head gasket - easier & probably less expensive in the long run to make one job and get it over with.

When you have the head off - chances are you will be able to visually identify where/if the head gasket has failed - even if it's obvious, get a straight edge and check both the head & the block for distortion.

Regarding the "air from the oil cap" - why do you think is this worn rings and not a cracked head or block - and no, I'm not suspecting either one to be cracked - just want to hear your thoughts.

One possible explanation as to why there might not have been air leaking into the cooling system is that the conditions of pressure & temperature under which the leak occurs were different - combustion pressures are significantly greater than those of the test rig.

Ok, I believe you are definitely right to plan to replace the head gasket while looking at everything else. That's been my plan but the compression test/leak down had me confused. And while I'm at it I should replace the intake manifold gasket on the off chance that is the issue? Or should I be replacing the carb and intake manifold entirely?

For the air from the oil cap, I've just heard that means bad rings.. I figured a cracked head or block would leak out of the radiator with the leak down since I've got oil/coolant contamination. That's my reasoning anyways, and I often don't know what I'm talking about haha. I suppose since there is leakage from the oil cap that this could be greater than the leak to the radiator, if present, so it shows no signs on the test? Or, as you mentioned, the conditions are different under compression.

I will note that I seem to be losing coolant without running the engine. I haven't been running it since I noticed the coolant leak and I'm still slowly losing coolant. Not sure what this means, but it leads me to believe the condition exists without compression and should then register under a leak down test...

I just got feeler gauges and a good straight edge though so I'm prepping for the head gasket replacement once the weather gets tolerable. Any recommendations on gasket brands?

Around here we buy a "top overhaul" kit that contains most of the gaskets required to be replaced when removing the head - the intake manifold gaskets are in there, so there's no reason not to replace them whilst you have the head off - brand wise, I would suggest you take a look at whatever RockAuto has to offer, their stuff is usually good quality.

Regarding the leak down test, if you can hear the air leaking at the oil cap, worn rings would be the most common cause, but, if the head/block were cracked in the right place, you could also have air escaping into the valve cover and out the oil cap - air leaking into the intake/exhaust system is most likely leaking valves, but, it's also possible to have a cracked head cause it (it all depends on where the crack is), you're not going to know until you pull the head to have the valve job done - I don't place a whole lot of emphasis on leak down tests, I personally feel I can get most of the same information from a compression test, which is easier to do.

Coolant loss without running the engine just means that there is a leak that is large enough to allow loss due to gravity flow - it does not necessarily mean that that leak is the source of your contamination, and as far as showing up in the leak down test goes, the leak down test does not pressurize the cooling system (unless there is a massive leak between the combustion chamber and the cooling system - which would/should have been reflected in the compression test results).  There are test sets that pressurize the cooling system - essentially a hand pump with a pressure gauge that fits in place of the radiator cap - you pump the system up to roughly 15psi and then observe the gauge, if it's dropping back the system is leaking, and you can then attempt to visually locate the leak without having to run the engine or work around a hot engine.

Ok, getting a kit has been my plan so I'm glad you recommend that.

My biggest concern with all of this is making sure I isolate the problem so that, if its a blown head gasket, it won't happen again. I would hate to do all the work and not find the reason the head gasket actually failed. I've got my straight edge and feeler gauges to check for warpage but other than that I'm not sure what to look for when I take everything apart.. other than visually inspecting to see if the head gasket is blown. Any advice for doing this type of rebuild? I know I'll learn a lot in the process but would really hate to do all the work and not actually fix the problem..

Hoping to revive this topic.. I took my engine apart and was surprised to find that the head gasket looked like it was in good shape. Nothing was visibly "blown" or really distressed at all. I'm worried I might have a cracked head/block?

Can we safely assume you only have one Samurai and this is the one with the 8v 1.6 engine swap?

I'm inclined to say that cracked head/block issues on the 8v engines are rare.