Would like to try a compression & leakdown test at home.

[sugarwood]

There are many seasoned experts here, but some of us are relatively new to this hobby.
For my own edification, I would like to remove the mystery of both these "exotic" procedures by attempting both on my car.
I have read a bunch of very old threads, but wanted to start a new one for my very stupid and obvious questions.

First, I will start with the tools required.

Can someone recommend a compression gauge that works with the 3.2 engine?

Is this the dual gauge leakdown tool I need to buy. ?

Do I need an adapter to connect the leakdown tool to my 3.2 spark plug hole? Do you make one or buy one?
What is this part for?

I have never removed a spark plug from the 3.2
As a first step, before ordering tools, does it make sense to make sure I can loosen all 6 spark plugs using the toolkit?
If they are seized, then buying these tools would be a pointless.

[sugarwood]

I have never dealt with TDC or anything related to the distributor.

How exactly does one turn over the engine to find this marking (rotate the crankshaft pulley) ?
Do I need to remove any belts before doing this?

[cpcooper]

I'd say start with a good quality spark plug socket with a foam insert to hold/protect the plug. 911 spark plugs are about 5 inches below the cam covers, so the insert keeps the plug from dropping out of the socket when you reinstall it. Also, a 3/8 ratchet, maybe with a flex head, and 4 inch extension. CAUTION: You are going to be removing spark plugs from an aluminum head. They should be initially tight, but then thread out smoothly. If it doesn't feel right, might be best to gently re-tighten and, provided the car runs OK, reconsider doing the tests. On the way back in, turn the extension by hand so you can feel the sparkplug thread into the head and you are ABSOLUTELY SURE it's straight before tightening with ratchet.

The leakdown setup you are considering looks like the same one I got from Harbor Freight. I also got my compression gauge there (no special adapter required). I like Harbor for stuff I seldom use. Snap-On for things I use every day, or Craftsman if I can't afford Snap-On.

The other tool you provided the link for looks like it screws into the spark plug hole and then you can attach a leak down tester or compression gauge to it. This would be handy, although not essential, as both the compression and leak down testers have a brass fitting on a rubber hose you have to finagle into the spark plug hole which, as previously described, is down at the bottom of a hole where you can't see it.

Go slowly and follow instructions that come with both test instruments. Above all, don't force anything on the way back together. Wish you were closer, I'd share my tools. Maybe someone else on the forum is close to you and will volunteer.

[sugarwood]

Now I'm a little intimidated about stripping the threads. I will be extra careful when rethreading the spark plug, and make sure not to force anything. It should spin in pretty freely for the first few turns?

[cpcooper]

Didn't mean to overdo it on the sparkplug thread thing. How about this: Once you've broken the plugs loose with the ratchet and they are turning freely on the way out, remove the ratchet from the extension and turn it with your hand. You'll feel a little resistance but you should be able to continue to unscrew the plug by hand. This is how they should feel going back in. You should be fine if you take your time and, if something feels wrong, ask for help.

I turn my engine over by hand by turning nut on the alternator pulley.

[sugarwood]

Will do on the spark plugs.

I didn't realize that turning the fan nut can turn over the engine.
Is this the standard method?
I will go try that now.

[sugarwood]

I tried turning the fan bolt and the fan pulley just slipped as the belt stayed in place.
I guess this means my fan belt is too loose ?
In fact, after a belt change, is moving the crank pulley a good test to see if your belt is tight enough?

[mdwracer]

Remove all spark plugs, this makes engine easy to turn over.

Leakdown should be performed on a cylinder when its at its firing time ( its TDC ).
Pull the distributor cap and line the crank TDC mark WHEN the rotor is pointing to number 1....Insert Leakdown tool for #1 and perform test.

Rotate fan clockwise...while pushing in on belt(keeping it from slipping)
The next mark on crank that lines up will be Cyl 6. Perform test on that cylinder.
The cranksaft turns two revolutions to fire all six cylinders, so you will do #1, #6, and #2... then one second revoultion of crank sprocket do #4, #3, and finally #5...

At some point while the plugs are out, perform the compression check... NOTE: make sure your compression guage when fully inserted does not extend any further than a normal spark plug does...(You don't want contact!!)
I also like to crank engine with the throttle wide open for test on all cylinders.

Mike W

[VFR750]

When you wrench the fan, push on the belt like a tensioner would. That's how you get the belt to grip and turn the engine.

[VFR750]

If you thread plugs by hand it's hard to cross thread them. Just need to see how it feels.

If there is anti seize on the threads or some carbon build up they may resist a little when coming out.

New plugs without anti seize should go in pretty easy.

[Ton504]

Originally Posted by mdwracer

Remove all spark plugs, this makes engine easy to turn over.

Leakdown should be performed on a cylinder when its at its firing time ( its TDC ).
Pull the distributor cap and line the crank TDC mark WHEN the rotor is pointing to number 1....Insert Leakdown tool for #1 and perform test.

Rotate fan clockwise...while pushing in on belt(keeping it from slipping)
The next mark on crank that lines up will be Cyl 6. Perform test on that cylinder.
The cranksaft turns two revolutions to fire all six cylinders, so you will do #1, #6, and #2... then one second revoultion of crank sprocket do #4, #3, and finally #5...

At some point while the plugs are out, perform the compression check... NOTE: make sure your compression guage when fully inserted does not extend any further than a normal spark plug does...(You don't want contact!!)
I also like to crank engine with the throttle wide open for test on all cylinders.

Mike W

New Guy here.

I was wondering why do you need to perform a compression test if you just completed a leak down test? The leak down test gives you all the info the compression test would, no?

And again I'm new here and also new to flat sixes. Should you hold the crank so it would not turn over once the cylinder is pressurized?

[doublebuffle]

Originally Posted by VFR750

When you wrench the fan, push on the belt like a tensioner would. That's how you get the belt to grip and turn the engine.

For sure, if you press in on the belt while turning the fan bolt pulley, removing sparkplugs is not required. My favorite way is using a breaker bar and the fan nut. My least favorite way is using the fan tool in your porsche tool-kit.

Arriving at the notches with accuracy is something that takes a little practice. Don't go backwards.

[doublebuffle]

Also, if you have the original spark plug tool, a special plug wrench is not required. The factory tool works very well.

[mdwracer]

In a perfect world with each cylinder on its TDC, the crank won't move when you put the air to it...
I really like doing a compression check first and doing a leakdown on the lowest reading compression cylinder on a presumably good engine/engine that has been running recently.
Leakdown tests are good for buying engines that are on pallets before you put them in the car only to find out that you have a burnt valve!!
It is fair to say that an engine could have higher than desirable leakdown percentage but still achieve a decent compression number.

Mike W

[Taxi!]

Sugarwood,

Not to make you more reluctant, but when I removed my spark plug boots for the first time so I could change the plugs, a couple of the boots ripped, leaving a 1/2 inch rubber ring around the top of the spark plug. This made using a spark plug socket with an insert to grip the plug after it's been unscrewed from the head (like cpcooper suggested) impossible because the leftover boot prevented the socket from completely fitting onto the spark plug. So I had to buy a spark plug socket without an insert to unscrew the plug and then use needle nose pliers to fish the plug out. Not a big deal in the long run, but I didn't immediately notice that the boots had torn so I spent a while trying to figure out why the spark plug socket was turning but nothing was happening. An extendable mirror helped figure it out.

[sugarwood]

It was pretty easy to move the crankshaft pulley!
For a while, I was pressing the left side of the belt, and the fan pulley just slid.
Finally, I pressed the other side of the belt (the one that is more obscured. passenger side), and it moved very easily.
Thanks, I feel a sense of accomplishment from something as trivial as this.

doublebuffle was right. I went right past the fan housing marking. It almost seemed to snap right past it.

[sugarwood]

Taxi, I will be careful while pulling the boots. Thanks for the head's up.

My next step is to try to loosen the spark plugs with the special toolkit thing.
Are there any basic tricks?
It seems like very limited access, at first glance. Do I remove anything else first?

The allen key is used to get some proper torque to break the spark plug loose?
Is that ever not enough?

[sugarwood]

The 911 spark plugs are the first in my life that genuinely scare me.
I have changed spark plugs on many cars and machines since I was a teen.
But, I have never seen spark plugs that are 100% hidden under a valve cover.

First the good news! I tried the spark plug tool tonight.
Boots came off very easily, and both plugs I tried break loose very easily.
I was barely able to get some leverage using the L-key, but it was enough.
I used my other hand to stabilize the plug tool on the plug so I wouldn't crack it with crooked twisting.
I screwed them back in, and gave a light tug once it was seated.

It took me a long time to get the middle boot reseated on the plug.
I just couldn't find the seat, and I must have been finding a false seat.
It finally clicked into place when I dramatically changed the angle of the boot.


When working with blind spark plugs, here are things that scare the hell out of me:

1) What would you do if you cracked the ceramic part of the plug? How would you fish it out?

2) How do you even re-thread the spark plug?
I can totally see never being able to get it back in, and just spinning it blindly.
It was hard enough getting the boot back on!

3) What if the spark plug falls out of the tool, while still in the cavity? How would you extract it ??

[wdfifteen]

Originally Posted by sugarwood;

I have changed spark plugs on many cars and machines since I was a teen.
But, I have never seen spark plugs that are 100% hidden under a valve cover.

I've never thought of that. I started with Dodge slant sixes, then VWs and 356s. Having the plugs hidden seems totally natural to me.
Nice photo!

[boyt911sc]

Originally Posted by sugarwood

The 911 spark plugs are the first in my life that genuinely scare me.
I have changed spark plugs on many cars and machines since I was a teen.
But, I have never seen spark plugs that are 100% hidden under a valve cover.

First the good news! I tried the spark plug tool tonight.
Boots came off very easily, and both plugs I tried break loose very easily.
I was barely able to get some leverage using the L-key, but it was enough.
I used my other hand to stabilize the plug tool on the plug so I wouldn't crack it with crooked twisting.
I screwed them back in, and gave a light tug once it was seated.

It took me a long time to get the middle boot reseated on the plug.
I just couldn't find the seat, and I must have been finding a false seat.
It finally clicked into place when I dramatically changed the angle of the boot.


When working with blind spark plugs, here are things that scare the hell out of me:

1) What would you do if you cracked the ceramic part of the plug? How would you fish it out?

2) How do you even re-thread the spark plug?
I can totally see never being able to get it back in, and just spinning it blindly.
It was hard enough getting the boot back on!

3) What if the spark plug falls out of the tool, while still in the cavity? How would you extract it ??

Sugarwood,

It is normal to be anxious when doing things that your are not used to do. Try to overcome your anxiety and do not over think every single step in the process. Relax and enjoy learning this new experience. Remove the intake valve cover and not worry about oil spilling out. With the valve cover removed, you would have a better view of the spark plugs. Facing one side of the engine, note the orientation of the spark plugs. They are threaded to the cylinder heads at a slight angle to the right.

You should be able to answer the above questions yourself using common sense. And if you could not figure out the answers to 2 of the 3 of the above questions, your are mechanically challenge and would take a lot of training and practice to become an average DIYer. But if you want to learn and do these maintenance work and enjoy the experience, you need to relax and tell yourself it is doable. You could do it. I was in similar mental state when I first attempted to work on 911. Maybe even worse because I get stomach upset and have to run to the bathroom several times before I could complete an engine drop. As of today, I am preparing a start up for the 14th motor I rebuilt.

We all would make mistakes and some are silly ones and others could be disastrous. I know for a fact which cam go to the right side or to the left side. And I still inadvertently installed them backward. The problem has been corrected and the rebuild is in its final stage.