DIY Leak Down test, part 2

[85_600]

I'm pretty sure I'm going to do this to my 600. I just have a simple question though. I know how to find out where the TDC of #1 is, but how do I know when the other pistons are at TDC as well? Is there a mark somewhere that would show me? Or, better yet, do the pistons 'really' need to be at TDC to find the 'escaping' air?

Thanks,
Paul

[puppet]

Our engines have a 180* firing rotation. The order is 1-3-4-2 (CW rotation)
There is a mark on the flywheel 180* around from #1 TDC. You can use that to position #3 and #2.

Heh ... better add that you need to lock the crank position before you pump the cylinder up.

[turbovanman²]

Easiest way is have someone bump the starter while you put your finger on #1 cylinder. When it starts to puff, your coming up on TDC. I also use a long philips screwdriver in the hole and slowly turn it over by hand. The piston has to be at TDC with both valves closed to do a leak down test. You can use the puff method on all cylinders and then finish off with the screwdriver.

[85_600]

What's the easiest way to turn the crank slowly? Can I turn it by a pulley or a socket on the crankshaft itself? If it's the crankshaft, I'm guessing the front passenger wheel and splash guard needs to come off, right?

Thanks,
Paul

[turbovanman²]

What's the easiest way to turn the crank slowly? Can I turn it by a pulley or a socket on the crankshaft itself? If it's the crankshaft, I'm guessing the front passenger wheel and splash guard needs to come off, right?

Thanks,
Paul


Correct, :thumb:

[85_600]

Actually, I need TDC on #1, this would put the 90 psi cylinder at BDC, as Russ has stated in a PM with me. I wanted to check that one out first anyways.

I 'may' be able to do this Saturday. I'll have to see what's up. If not, then not until July:(

Thanks guys!
Paul

[ssheen]

Sorry to bring this thread back.

How do you lock the crank position?

[mock_glh]

Put it in 5th gear (you do have a stick, right?).:) Even if it's not, if the crank is exactly at TDC, the piston won't go down.

[ssheen]

Thanks. :D

[ssheen]

Another question, is it necessary to have the cyl at TDC? Or can one just take the follower off so the valves are all closed?

[turbovanman²]

Another question, is it necessary to have the cyl at TDC? Or can one just take the follower off so the valves are all closed?

TDC with the valves closed. Remember, you have 2 TDC's, one with open valves, one with closed. Just crank it over, blipping the starter until you hear a whoosh, then finish turning over by hand. I use a long philips screwdriver in the hole when i turn it over by hand to find TDC.

[puppet]

There is another position to check 'em part way down the bore. If you line up the arrows on the cam pulley to engine verticle centerline you can check either #2 or #3. Depending on which one has it's valves closed, the other will be able to be checked 180* from that original position. So, opposite arrow up^.

To check #1 and #4 this way the arrow will need to be at 45* off verticle (1:30 clock). Depending on which one has it's valves closed the other needs 180* turn to be checked. So, opposite arrow at 45* off verticle.

*Make sure you can lock down the crank before you try this. The engine will turn. Like mock_glh suggests, 5th gear is good but it'll still want to creep backward. So, overshoot the positions 10* or so and it'll creep back to where it should be. If you have an automatic your only option may be to lower the pressure to 50psi .. then put the friend with the strong back and weak mind on the business end of a breaker bar :P

[ssheen]

I noticed the creep! I blocked the tires to stop that. Thanks for the help.

[turbovanman²]

If you have it at TDC, it won't move. Done 1000's of leak down tests.

[ssheen]

cool, did not know that. I took the followers off to test and had them on as well. I did noticed that, and was curious why, when they were on, the car did not move.