IainM

OK, I'm embarrassed to say I don't know how to do this. Did a quick search but came up with nothing.

I'm trying to do a leak down test and have replaced all the top plugs and now ready to test the cylinders but when I look at how to get a wrench on the crank I see there's no room.

How do you turn the engine over by hand? Do you use the fan/alternator pulley?

sorry for the newb question

crg53

Yes, use the fan/alternator pulley. It is a lot easier if you have the spark plugs out, but since you are doing a leak down test, you would already. It sometime helps if you pinch the belt a little so it will not skip on the pulley.

Quadcammer

big offset wrench seems to work

IainM

thanks Steen!

..and it's clockwise rotation, correct?

crg53

Yes, clockwise when looking forward.

sbarracl

And make sure you have the hand brake off been there...

Mike J

I do it in neutral - a lot less to turn over. Its very likely you will need to pinch the fan belt a bit to make sure the engine can be turned - as was said before, if at least one plug is out per cylinder, it should be fairly easy to rotate.

If you are doing a leak down, you will need to find TDC compression stroke for every piston. I start with #1, so that is the TDC marker on the pulley aligned with the mark on the fan shroud. You can either be bang on, or a full turn out. After positioning, do the leak down on #1, if its leaking a lot, rotate the engine 360 degrees again and retest. It should be better if not almost zero leakage. Now you found TDC #1 on compression stroke. Then rotate the engine 120 degrees clockwise until the next marker, and you are now at #6 and so on (1-6-2-4-3-5) through the firing cycle.

The other way to find TCD #1 is to pull a cap and see where the rotor is pointing, that will help you find the TDC for #1. I find its more time efficient to just rotate the engine till the first TDC for #1, and then test if I am on the correct part of the cycle, because i do not have to pull off a few vent holes, etc.

Cheers,

Mike

IainM

Thanks guys for all the advice. In the end I didn't actually take any pressure measurements ran out of time for other service activities (actually - too scared I'd set it just before TDC, charge it up to 100psi, spin the crank in reverse and blow my tensioners. )

But I did go through all the set up steps as you suggested and they all worked as described; with perhaps an embellishment. I was doing this after an oil change so I thought it would be good to crank the engine without the DME a few times until the oil pressure came up. I was able to get it to 3 bar after the 3rd crank of about 20 secs. Would this coat the cylinders with oil to improve leak down testing enough for a cold engine or is hot engine testing the only way?

I took the distributor cap off after this and saw I was close to #2. Pinching the belt i turned to where #2 should be and a mark appeared on the crank pulley lining up with the case mark. (Cue Da Vinci Code music) I'm loving working on this car.

It seems prudent to align the crank marker just past the case marker so that if the engine does turn, it will turn in the right direction. Am I being paranoid here? Does 6th and handbrake lock it for 300ft/pounds+ or whatever it is?

Just seems I could do a lot of damage with 100psi and a spark plug hose.

Mike J

If you are on the mark, it should not turn even with the pressure, since its a straight line from the top of the piston to the crank arm. If the engine turns either way, no damage done, just try again. You can have someone hold it at TDC, but I have never had to do that.

I do not see how you can do a lot of damage either way, the most it will rotate is perhaps 15 degrees or less, because the valves will start to open and let off the pressure.

Cold or hot is irreverent right now, its going to be a cold test since your engine has been off for a while. do the test, and if you get low readings (like 3%) leakdown, and consistent compression, then its all good.

Cheers,

Mike

IainM

Thanks Mike.
I'm going to come back to this when I get time as I'd like to monitor this as an indicator of engine condition. Based on what I saw doing the work and an extra 5HP in the butt dyno today (could loose plugs cause loss of low end torque?) I'm going to say everything is peachy.