Wankenstein

This is another Ezone directed question. I occassionally browse and post on the HT site (under a different name). I like to post ETCG's dry/wet compression testing instructional video when the OP has never performed one. I posted ETCG's video recently and I mentioned that another (Ezone's) method that I learned was instead of testing by a certain number of cycles on each cylinder is to allow enough cycles for each cylinder to reach max psi and then go a few cyles past that and watch for increase or decline.

Here's a respond that someone (not OP) posted:

(copied and pasted) "The purpose of ETCG's method (I tend to do 4 or 5 cranks) is that even a weak cylinder can eventually push up to an acceptable max pressure.

Doing a set crank amount closer emulates the running engine pressure IMO. Granted the running engine piston is moving much faster, but it only compresses in one stroke. A leaky piston will leak more on the higher speed (pressure) single pass than a non leaky.

When you only crank each cylinder 3-5 times (choose a number and stick to that for each cylinder) you will be much more likely to see a weak cylinder than if you crank it until it can't create any more pressure.

Also, I've noticed 4 or 5 cranks per cylinder tends to get me results that align with the factory service manual, where max pressure is beyond that in most cases.

Both methods work, I just think the 4-5 crank method provides slightly more accurate results."

ezone

That's why I watch the gauge while I'm doing the checks, note how much the needle climbs with each 'puff'.

But really, the statement quoted .... depends on the failure.......most of the time it won't be that way, but once in a while it may.

But LOW is still LOW no matter what. If one is really low, it's still gonna be low using either method.

And.....I've successfully diagnosed problems using my method that others could not when using the other method. (In one case, I was just standing nearby and watching their gauge during their testing, I could tell 2 cylinders out of 6 had a problem....but the person doing the test couldn't see it).



Same could be said for leakdown testing: low pressure vs. high pressure, each method has advantages and disadvantages.

Wankenstein

Thanks for the clarification Ezone. Since you brought up leakdown testing I have questions about an upcoming (my first time) one on my son's car: 2007 Mazda 3 with 2012 Ford 2.5L I4 engine... If, you'd be so kind to answer.

1) Does the crank need to be held in-place (socket wrench) for each cylinder when at TDC to keep the cylinder from being pushed down by 100 psi of air?

2) Do all the spark plugs need to be removed when testing or better to remove one at a time?

3) Is an auto stethoscope recommended for listening for air moving through TB, crankcase or tail pipe?

4) Any tips or suggestions to ensure a proper leak-down test?

ezone

No, or at least I don't. It might damage something if it takes off.
The piston in the cylinder being tested DOES need to be at exactly top dead center though.
If it is off by more than a hair, the air pressure will push it on down.
I remove all of them in most cases, because I am testing all of the cylinders.

I have my compression tester whip in the cylinder I'm going to test, I listen for air to rush out while I'm turning the crank so I know when the cylinder is on the compression stroke (both valves closed, piston rising). Also, if you watched my little video, notice I drop a screwdriver into the companion cylinder so I have visual confirmation when the two pistons are at TDC. When I reach TDC and the screwdriver just starts to go back down, I back up and rock the crank back and forth just enough to find the absolute highest point of piston travel....watching that screwdriver.

A simple length of tubing can be more effective, and FREE. Hold one end to your ear, or to your nose. The other end to the area in question. The nose can detect quite small amounts of air movement LOL

Don't forget other simple and effective means, like taping a plastic bag to the tailpipe. If it inflates during a check, you know the air got there through a leaking exhaust valve.
You have low compression in one cylinder.....Your main goal is prove there is leakage, and figure out exactly where the leakage is going.

Did anyone check valve clearance on it yet?

Wankenstein

Not yet. My son's been busy with work and school (over an hour away from mechanic) to bring to mechanic. Last Monday I put together the leakdown tester from HF parts and was ready to try a leakdown test on his car's engine. However, the HF compression tester whip does not fit into a standard quick disconnect so, I spent most of the day coming up with a solution and finally found one that only cost around $5. I plan to test the engine this coming Monday. Also, will do another dry/wet compression test using one teablespoon of oil.

Thanks for the great tips. I'll post the results hopefully Monday if all goes well.

ezone

Another note....
My working time is critical, I strive for efficiency, try to plan ahead and make every move count. (labor is valuable)

I usually start my testing on a hot engine. "As run".
If it has a problem cold or tests need to be done cold for some reason, it can sit and cool off for that test, and I already have hot tests done and results recorded.
(and work on something else in the meantime)

If I were to add oil to any cylinder for one test, I'd do that LAST. Oil may skew results of other tests (false sealing). Nobody stands in front of the engine dumping oil into cylinders while you are driving, so I need "as run" testing.

If oiled, I'd want to run the engine to operating temp again just to clear out added oil and maybe get it warmed up again....to an "as run" condition again before more tests are done. Reinstalling plugs and all that takes valuable time, so I leave oiling for last if it is done.

Not everything is cut and dry.
Things don't always go "according to the book"....Adapting on the fly is sometimes very necessary.
Results of one step may determine the next step of the process....and as always, "it depends".

Wankenstein

Thanks again Ezone. I figured the wet test would be last as well.

Wankenstein

Finished the leakdown test earlier today. I'm not sure what's up with the tester I put together.. when I test it without it hooked up to a cylinder it reads correctly on 100 psi tank output gauge, 100 psi LDT regulator (full clockwise) gauge and 100 psi LDT pressure gauge. However, when connected to a cylinder the LDT regulator gauge reads 100 psi and the LDT pressure gauge reads zero.

I unhooked the tester and just connected the whip to compressor. Manual transmission left in neutral. We used 100 psi air pressure, engine at operating temp, all spark plugs removed. The PCV valve hose cannot be pinched off due to it's location behind the intake manifold. We removed the oil cap, dipstick, coolant reservoir cap, opened TB flap.

On all four cylinders (when at TDC) air did not escape from the TB or tail-pipe and only slight amount of air coming from crankcase. There were no bubbles present in the coolant tank. There was air leakage between cylinders and I'm not sure if this is normal or not? When we tested cylinder 3 (companion cylinder is #2) we heard air escape from spark plug holes (cylinders) 1 and 2 but, not 4. When testing cylinder 2 air was escaping from 1 only. Testing cylinder 1 air was leaking from 2 and 3. Testing cylinder 4 air was leaking from 2 and 3. Is this a possible head gasket leak causing compression loss?

Lastly:
Repeated dry and wet compression test on cylinder 3 (only)
Dry = 100 psi
Wet (1 tablespoon oil) = 100 psi

Update: found this thread after posting http://www.mr2oc.com/61-3sgte-turbo/...-cylinder.html Reply #10 might be related:
(copied and pasted) "Okay, so it turns out that I totally goofed the test. I went back to the shop to redo the test. This time I decided to take off the distributor cap and see where the arm was pointing to make sure I was TDC on the compression stroke. I started with cyl 4, and noticed that as soon as I hooked up shop air to it, my distributor position moved. DOH! I never put the car in gear! This is what was causing the valves to open and loop back around to the other cylinder!"

ezone

Depends on what is leaking on the cylinder being tested, and which valves are open on other cylinders at that crank-cam position.

At that point you found air coming up from some other spark plug hole, you need to reinstall the plugs on the 3 cylinders you aren't testing so you can figure out which valve is leaking in the cylinder being tested.


When the whip is open, that's 100% leakage. If you seal the end of the whip, the LD gauge should read the same pressure as the line pressure (zero leakage). When you have the whip screwed in a plug hole and air it up, you need to make sure the valves are all closed (firing position after compression stroke) and the piston is dead nutz at the top. If any valves are open that's gonna show as leakage, probably 100%....and that could be valve overlap (between exhaust stroke and intake stroke instead of compression/firing)

Wankenstein

Okay. We will repeat the test with other 3 plugs installed.

I used the whip with a balloon at the end to find the beginning of the compression stroke. Used a long plastic object to insert to target and companion cylinders. Rocked to find TDC peak as best as possible.

The DIY tester calls for epoxy to be used in a coupler, let dry and drill out with a 1 mm bit. I did that and hope it's not the issue.

Wankenstein

This read is good http://www.hotrod.com/articles/cylin...akdown-tester/
I didn't think to rock the valves while blowing air in to find complete valves closure as you stated. It may not have mattered anyway with all the spark plugs removed. Trying it again Monday.

ezone

If you have the valve cover off, you could just jiggle the rockers up and down to be sure all 4 valves on the cylinder being tested have some free play (clearance).


If leakage is found through the valves, sometimes pulling UP on the valve stem/spring can reduce the amount of leakage. Carbon chunks can cause headaches if they get caught in the valve sealing area.

Wankenstein

Okay. Wouldn't take much to remove the valve cover. How much free play is expected?

Another way to find TDC:

ezone

How much? "Any." On all 4 valves.
The only concern is that the valves are not held open by a cam lobe during your leakdown test.

If they have ever been adjusted to specs, then I'd expect that same spec of clearance. (Note: Good time to do this?)

A valve that is held open by a cam lobe won't have any free play in the rocker arm.
If your cylinder is on overlap or close to it, one pair of valves or the other won't have clearance.

Wankenstein

Okay. Gives me a better understanding after reading your explanation.

My assumption would be that a "good" machinist would do a proper adjustment before returning the cylinder head. Unfortunatley, I'm not sure if it was brought to a good machininist or one at all. Being that the engine only has 50K miles on it I doubt it's been adjusted prior.

The video below describes a bit about checking clearances for this specific engine but, doesn't describe how to adjust clearance. As you know, on a D16Y8 there's adjustment screw/nut which I don't see on the MZR. I found some info which I believe is related: http://forum.miata.net/vb/showthread.php?t=554902 post #3 " The issue is that the system uses tappets in incremental sizes. You either spend a lot of money and order a lot of sizes, or you measure accurately and then order the specific tappet size to get the clearance back in tolerance. There are 16 tappet sizes ranging from 3 - 3.725mm"

Vid:

ezone

Oh crap, I keep saying rocker arms, forgetting you aren't on a Honda engine. Oh well.
Clearance is the important word.


Unless the machinist specializes in one particular engine, he isn't likely to have the necessary shims on hand to make adjustments with.
That's part of the installers job IMO. (unless previously arranged and agreed upon with the machinist)
The machinist might be able to grind a little off the tip of the valve stem to increase clearance (this is very necessary when grinding valves and seats), but that's probably the extent of what he can do.

When I get a brand new head (complete with cam and valvetrain) from Honda, all the adjusters are backed out far enough to get most of the valves closed.
If they were all pre-adjusted to specs, there would be valves open far enough they could be damaged/bent during handling and shipping.

When I send a head to the machine shop, I strip it myself and reassemble/adjust it myself. If they have to take something else apart, they usually leave it obviously loose so I know it has to be reassembled.


Other engines I have dealt with that used bucket tappets with shims.. Various tools/methods were used to push a tappet down and swap shims and each seem to use their own unique shims:

95-? 1.5 Mazda Protege (was the first of the new generation of non-hydraulic tappets)
Mazda/Ford small diesels, up to mid 80s (for some reason I still have a few random shims in my toolbox LOL)
VW water cooled engines, various, starting in mid 70s
Isuzu 3.2L
Various Toyotas
Search how some of these engines are supposed to get their valves adjusted, the correct tools used and whatnot. (I fabricated/improvised a set of tools to do the 1.5 Protege shortly after I left that dealership)


As I said before, at the dealers I worked at we had boxes of shims with several of each available thickness to choose from. Adjust valves: take one-leave one.

Except at my current dealer. I've never seen any shims for the Isuzu engine at this dealer, but then we don't ever see the old Passports anymore either.

Wankenstein

Well, I can start by checking the clearances and hope they're in spec. Repeat the leakdown with cover off to watch cam lobe/valve position.

Wankenstein

I didn't do the leak-down retest this past Monday. Today my son and I brought his Mazda to the mechanic for a leak-down test. First off the mechanic is again insisting that the cams (DOHC) need to be removed and the timing chain off to do a proper leak-down test because if not the pistons will always be forced down with air and won't stay at true TDC when checking for a compression ring leak.

The mechanic didn't use an LD tester..just shop air and turned the crank while all the spark plugs were out. He didn't removed the TB air inlet hose or open the TB flap. He didn't remove the coolant tank cap or the oil cap.

While running air (starting on first cylinder) he turned the crank and rocked the valves. He didn't use a long screw driver to establish TDC or listen for compression stroke. He did the same for each cylinder and as with the initial LD that my son and I did, air leaked from other spark plug holes no matter the piston/valves location. After he stopped testing it he said bring it back next weak and take the cams and timing chain off and repeat a leak-down test.

We told him it still has cooling loss and he said he may end up pulling the head after the next leak-down test. I then asked him if the machinist or he replaced any valve shims or adjusted valve clearances during the previous HG replacement. He said it doesn't have shims (what?) and they aren't adjustable. I told him that it does have shims and they need to be adjusted correctly and clearances correct the first time or they aren't right. I had my doubts about him previously and now my doubts have been elevated. He then said the machinist can ground the valve face for clearances.

If he pulls the head and sends it back to the machinist I am insisting this time to talk with the machinist and get a copy of the invoice both old and warranty work. I still plan to try another LD test this weekend myself.

ezone

cough*BULLSH!T*cough

Same for the rest.
Your mechanic is broken. Replace mechanic.





EDIT:
Was that too harsh? Give the guy a participation trophy as you remove your car from his shop?

Wankenstein

Lol.

Oh well it's all for not now. My son just hit someone from behind and the car is totaled. Fortunately no one is hurt. His 5th accident in four years. He's probably going to get his license revoked. I can't even stand to talk to or see him at this point. Apparently, he doesn't appreciate the privilege of driving.

I won't use that mechanic again for anything.

ezone

Damn....Glad nobody was hurt!

Well I guess that solves a few problems, doesn't it? LOL

Wankenstein

Yes and created a new one.. now my son wants to ride a motorcycle. Might be good for him in ways to make him more attentive on the road.

The cop ticketed him as "following too closely". Take a class and it won't hurt points or raise rates.
A bike is cheap to operate and insure. Do they require a lot of upkeep?

Now (hours later) my son said the front end damage isn't bad. The engine wouldn't start but may be do to MAF or intake hose damage. He said no leaks of any sort on site of accident.

ezone

I think after "His 5th accident in four years", a motorcycle is the last thing he should be getting if he wants to stay alive.


Think "bicycle". LBVS.

Wankenstein

Yep..he's rethinking the motorcycle option. Turd junior works an hour away from where he lives so, that's part of the problem. He does well though in tips and wages and the lady who owns the restaurant is contemplating opening another one near him and wants him to be in charge of the wait staff if that happens. I told him to find work closer to him and ride a bike, bus or Uber to get around.

I worked in Singapore for 4 years and never owned a car (too expensive) and occassionally missed driving but, never missed upkeep, insurance and fuel prices. Rode the Metro rail, buses and cabs. Unfortunately, different public transportation scenario in most U.S. smaller cities.
I worked in hospitals (X-ray and CT) there and saw a lot of bad injuries caused by motorcycle and scooter accidents practically everyday.

I saw the car this morning and it's totalled. Front end driverside steering parts pushed up into firewall LOL.