TheSamba.com :: View topic - AARGGHH! Leak down test....where did i go wrong. PIC added

Mon Feb 22, 2010 4:29 pm

:x Was just doing a Leak down test on my engine, 72', 1800, typeiv. First time ive ever done one. spark plugs out, engine reasonable warm but not hot, put the tester into number 1 and turned her on and the compression turned the engine and took 1 out of the firing position. set it up again and put a screwdriver though the fan to stop the engine from turning, i though i had read somewhere thats how to do it. turned it on again and CRACK.... I have the engine turns over again and shears 7-8 blades off my fan. Gutted to say the least. Some of the blades from the fan are inside. What now! remove the fan and get the bits out? can i drive it temporarily with it missing that many blades? Do i need the engine out to get the fan off and the bits out? In hindsight looks like the screwdriver through the fan was not the way to stop the engine turning over :( How do you stop the engine revolving so you can get a reading? the compressor was set to 90 psi.
Cheers for any responses, I am so fukced off right now!!

Mon Feb 22, 2010 4:37 pm

I'd say putting the screwdriver in to stop the fan was your biggest mistake. Now ... with blades missing (broken off) your fan will be horribly out of balance. Time to take things apart and see what you need to replace. I would not drive it. Why would you want to stop the engine from rotating while you're doing a compression test?

Mon Feb 22, 2010 4:39 pm

Sorry, Leak down test, not compression test. Im so pissed off i cant even think straight, hence wanting to stop the engine turning.

Mon Feb 22, 2010 4:40 pm

Probably leak down - not compression.

Mon Feb 22, 2010 4:40 pm

Ouch! :shock: I think ummmm take the screwdriver out before turning it over for the next cylinder? Hope it can be welded. I wouldn't run it. It's dangerously out of balance now.

Mon Feb 22, 2010 4:40 pm

I presume he was doing a leak down test and not a compression test. Put the transmission in high gear, put the parking break on, and chock the wheels.

Mon Feb 22, 2010 4:41 pm

1. Buy a new fan
2. Buy a for sale sign
3. Put sign in window

Mon Feb 22, 2010 4:41 pm

Ok ... so ... you cranked the engine over while doing a leak down test? With the screwdriver in the fan?

Mon Feb 22, 2010 4:43 pm

Sorry. leak down test, so obviously the engine was not running so the bits arent in the engine just in the fan housing. Its a long way from dead or needing a for sale sign but thanks for the advice!

Mon Feb 22, 2010 4:43 pm

brandn wrote: Sorry, Leak down test, not compression test. Im so pissed off i cant even think straight, hence wanting to stop the engine turning.

There are plenty of used fans out there. Do not run the engine for any length of time with those many blades out. You can easily replace the fan with the engine installed. You can prevent the engine from turning by putting a phillips screwdriver in the hole in the flywheel accessible through the opening on the left side of the case up top and putting it in 4th gear with the brake set.
Colin

Mon Feb 22, 2010 4:43 pm

Whoever gave you the screwdriver advice has more than one screw loose. As mentioned, flywheel is a much better place than the fan.

Mon Feb 22, 2010 4:45 pm

didnt turn the engine over. Just opened the compressor to do the test and that turned the engine with the screwdriver stopping it to give me the leak down reading. How do you stop the engine turning when you do the test, obviously not my way!

Mon Feb 22, 2010 4:45 pm

Please don't run the motor with a broken fan. I did a leak down test and my #s did not make sense. But when you do a leak down the piston will go to BDC from air pressure. You are not looking for compression, but pressure being released from the cylinder. Sorry for your situation. If I am wrong someone please correct me.

Mon Feb 22, 2010 4:46 pm

Its definately beyond welding....Trying to sort a new one now...

Mon Feb 22, 2010 4:47 pm

Got it ... follow Colin's (among others) advice. Go poke someone in the eye for the bad advice on the fan blade trick.

Mon Feb 22, 2010 4:47 pm

If you dont stop the engine turning, you just get 100% reading?

Mon Feb 22, 2010 4:48 pm

Amskeptic wrote: brandn wrote: Sorry, Leak down test, not compression test. Im so pissed off i cant even think straight, hence wanting to stop the engine turning.

There are plenty of used fans out there. Do not run the engine for any length of time with those many blades out. You can easily replace the fan with the engine installed. You can prevent the engine from turning by putting a phillips screwdriver in the hole in the flywheel accessible through the opening on the left side of the case up top and putting it in 4th gear with the brake set.
Colin

Right. cheers for that, looks like i didnt read where to put that screwdriver....

Mon Feb 22, 2010 4:49 pm

babysnakes wrote: Please don't run the motor with a broken fan. I did a leak down test and my #s did not make sense. But when you do a leak down the piston will go to BDC from air pressure. You are not looking for compression, but pressure being released from the cylinder. Sorry for your situation. If I am wrong someone please correct me.

A leakdown test done at BDC is not going to tell you anything about the condition of the rings and cylinders at TDC. You need to stop the engine from turning away from TDC to get meaningful results.

Mon Feb 22, 2010 4:50 pm

No, the engine will only turn to Bottom Dead Center and then stop turning. You don't need a compression stroke. You are just looking for air going between valves and rings.

Mon Feb 22, 2010 4:51 pm

you want the engine free to leakdown correct? The air holds the piston at the bottom, you might get a little turn when you first hit the air, but that compression will stop that motor fast...

New fan, vacuum/clean out the old guts, drive on...