compression test recommendations?

70SWT · 09:54 AM

EDIT to clarify: looking for tips on how to do a compression check on an engine on a stand i.e. out of the car (if possible) without taking it to a shop, and recommendations for specific products available at a reasonable cost.

Thanks, Al

John_AZ · 02-14-2009, 07:50 AM

AL,
I picked up the leak down kit at Harbor Freight in town. If I need a one time item I go to Auto Zone and put a deposit down.

The only "tip" I have is to make sure you remove the DME relay or you will wash you cyl with injector gas and per charge your battery if you do both tests at one time. A remote starter switch is also handy and I have videod the readings for future reference while doing the test.

GL
John_AZ

70SWT · 02-14-2009, 09:54 AM

Thanks for the tips - see edit as above.

mikepellegrini · mikepellegrini's Garage

Can you put the bellhousing on and install the starter? That's the only thing I can think of. Without the starter, cranking manually would be a real drag (pun intended).

You could have the engine suspended from an engine hoist if the stand mounts got in the way - and just jump the electrical connections.

Compression guages are pretty cheap - I think I paid maybe $50-60 for mine. But as John pointed out, Autozone also rents them (for the price of a deposit which is refunded when you bring it back).

Like John said, the only other alternative would be a leakdown test - which isn't quite the same.

70SWT · 02-15-2009, 04:53 AM

How would you go about leakdown testing with the engine out of the car? That question was also a part of my original post, which I inadvertently edited out...

John_AZ · 02-15-2009, 04:56 AM

Another option, I think, may be to get a air hammer, attach it to the front crank bolt-24mm, turn the pressure up on the air tank to the max the tool can handle, and see if it would turn the engine over. I do not think a small home compressor would handle the engine compression but if you had a large, floor model it might.

This is only a random thought and may not even work unless it was on the PBS Red Green show

.

John_AZ

mikepellegrini · mikepellegrini's Garage

Quote:

Originally Posted by RSflared72E

How would you go about leakdown testing with the engine out of the car? That question was also a part of my original post, which I inadvertently edited out...

You just turn the engine so the valves for the cylinder you're testing are both closed, then pressurize the cylinder and see how fast it leaks down - and from where. The leakdown test equipment they sell will have adaptor fittings and guages to measure the loss.

You really need a compressor to do a leakdown test.

Jeff Laurence · 02-15-2009, 09:34 AM

Don't forget to lock the crank if you do a leakdown test-- if the piston gets a little past TDC, it will get really exciting real fast.

mistertate · mistertate's Garage

Quote:

Originally Posted by Jeff Laurence

Don't forget to lock the crank if you do a leakdown test-- if the piston gets a little past TDC, it will get really exciting real fast.

In other words you better have a timing belt on there...

many944s · 02-15-2009, 05:30 PM

^ actually, with an engine on the stand the easiest way to check the leakdown is without a timing belt... and without a cam tower

That way you can be sure the valves are closed. Also, since 1&4 are at top dead (crankwise) at the same time, you can check both of them first, then rotate the crank 180 degrees to get 2&3 at top dead and measure them!

Afterall, if the engine is already out of the car, a $9 cam tower gasket is probably the least of your concerns!

-Nick