how's my compression?
 

Did a compression test yesterday on my coolant-imbibing GSL-SE and found it to be about 100psi as near as I could determine with my regular tester; all chambers were pretty much identical. I tested using the trailing plug holes. The car had not been run for a couple days.

How does this sound - acceptable, or must I replace the rotor seals as well as the gaskets which I was going to do anyway?

Because if I have to replace the rotor seals then I'd rather just get a used engine. I only need about two years out of this engine before I do a swap.

Thanks

J

PS I was 0625, changed my user name.

um, check out your cooling sysetm.


It could be lots of things.. make sure you check your O rings on your intake manifold. and check your radiator cap..


DON'T OVERHEAT the car either.



100Psi is very good compression.



-Zach

I guess I didn't tell the full story . . .

The gaskets need replacing, without a doubt, because the exhaust smells like coolant, and sometimes smokes white as well. It's using a fair bit. I suppose it was probably overheated at some point and an o-ring gave out.

As I understand the 13b EFI motor doesn't have coolant flowing through the intake manifold. Don't have my service manual yet, anyone want to confirm this?

I was just hoping that I didn't have to replace the rotor seals as well.

The car has about 100k miles.

So 100psi is good compression then? That is what I was hoping. Any other opinions?

J

ok, you are right about the coolant in the intake manifold..


Most likley if you are eating coolant one of your rotor housings is probably shot. Very likly both could be. This actually usually happens from people not changing their coolant and using bad water.


You can try the stop leak stuff, the aluminium kind works ok.. it could keep your engine running for the next year. but i doubt you will make it any longer then that..




Another option is picking up a jspec engine. they can be had for ~700 usually.


-Zach

OK so the edges of the housings would be corroded you figure?

Admittedly not knowing much about it, I'd guess that since there would be no coolant in between the inner o-ring and the combustion chamber, that part of the housing ought not to be affected by bad water in the system.

I suppose that would mean that replacing the o-rings wouldn't do me much good? And the only way to tell for sure would be taking it apart I guess.

J

You got it.. that is why i suggested a jspep motor..

rebuilding the current engine is very likely gonna need new/used parts that will cost you.


-Zach

Thats a really great compression reading. Did you use a rotary compression gauge so you are sure to get all three sides? Otherwise your just getting the highest chamber.

As far as burning coolant, what you have is either an overheated warped housing or a bad water seal. Both warrant a tear-down and rebuild.

I used a regular compression tester. I looked at the gauge as it was cranking. So each chamber will have been read in turn. All popped the needle up to around 100psi.

I'm hoping that was the right way to do it? (I'm new to this, can you tell)

re: the using coolant bit, is there any way to tell without disassembly which of the two possibilities it would be?

guess it doesn't matter as I'll have to pull it apart anyway

J

Yes you did it the best you can with a normal compression gauge.. and you are fine..


The important thing is actually the difference between the bounces and the difference between the front rotor and the rear..



And there is no way i know of to really tell what part is bad without dissasembling the engine.


-Zach

thanks Zach

well here we go then

J

100 psi is very good, you need to hold the valve in or remove it, crank it over and record the bounces via a DV camera or such. Play it back in slo mo and watch the bnounces to be sure all 3 pulses are even and around the same mark...

thanks Mike

want to lend me your camera? ;)

So if my compression is good, does that imply anything about the status of my housings, i.e. warped/not warped, corroded/not corroded?

thx

Jason

Nope means nothing. .just that you have good compression.. which could be a result of the coolant leak..


Coolant helps build compression when in the combustion chamber.. well any liquid does for that mater.. that is why people use atf or oil to start a flooded car. to help build compression.



-Zach

DJ Rotor, what part of Canada are you in?

You can take off the exhaust manifold and look in the exhaust port at the rotor to see which rotor you can see coolant on. Its probably easier to do when the engine is out of the car. The water seals are not expensive. The outer seals are around US$18.00each and the inner water seals are around US$6.00 each. (mazdatrix.com) If you open up the engine, you may as well replace them all. If the rotor housing is shot, then that will cost $$$, as well as having to replace a bunch of rotor seals. I wanted to know what part of Canada you are in cause I may be close enough to come buy your old engine off you if you get a new one.

Project84,

That's what I'm in the process of doing now. I've ordered a complete gasket set, and am going to pull the engine, take it apart, and put it back together with new seals.

I'm in Manitoba, not too far from South Dakota. Fairly close to the border. If I get the motor apart and it doesn't look hopeful, I might just get a used j-spec motor. If I do I'll let you know.

J