How to go about compression and vacuum gauge testing in cold engine.

[juntjoo]

So I was recently diagnosed with bent valves and before I decide what to do be it find a rebuilt head or repair it, I would like to get familiar with diagnosing head problems and discover 1st hand what's exactly wrong with mine, -not psychologically, mechanically.

So I was reading through my Haynes manual and reading over the said tests, and the leak down test I'm assuming, and it says your engine should be warmed up to get you proper readings. But my car won't start! So is this just a matter of expecting a lower compression environment as I perform these tests and not going by the exact numbers listed for these tests(minus the leak down test)? Mind you I'm not familiar at all with the vacuum gauge tests, yet.

I just want to make sure I'm not wasting my time doing these tests if it is almost necessary to have your car warmed up prior. Thanks

 

[DSM1G90]

If you have been diagnosed with belt valves, we need to get the head replaced/repaired before any other tests are performed.

Main test for head problems is a compression test with a compression tester. It's quite an easy task to do if you have access to a compression tester along with having a buddy to help you out with this test since you (or him) has to crank the motor around while the other runs the tester.

True, the other test are with the motor at operating temperature... you can wait for those way down the road-you're in no big hurry.

-DSM

 

[Infamous33]

My first question would be this... Is the timing belt still on and intact?
If the belt broke or lost a couple teeth and you aren't spinning everything on proper timing, than a compression test would prove almost useless.
If all is well with the belt, the compression test will show which cylinders have catastrophic failure.
As for doing a leakdown test, if you are showing little (20-40psi) to no compression on more than 1 cylinder, the leakdown test won't do much good. No compression would mean pulling the head and you will find out which valves are bad after that. If there is low/no compression on only 1 cyl (I sort of doubt this, due to the car won't run) a leakdown would give you an indication of perhaps a burnt valve or valve spring issue.
When doing a leakdown test, the air will flow out the tailpipe for a bad ex. valve or out the intake for a bad int. valve.
Good luck

 

[juntjoo]

If you have been diagnosed with belt valves, we need to get the head replaced/repaired before any other tests are performed.

Main test for head problems is a compression test with a compression tester. It's quite an easy task to do if you have access to a compression tester along with having a buddy to help you out with this test since you (or him) has to crank the motor around while the other runs the tester.

True, the other test are with the motor at operating temperature... you can wait for those way down the road-you're in no big hurry.

-DSM

Well, the reason I want to perform these tests before I replace anything is to verify what the mechanic told me and to get familiar with diagnosing these issues myself. And I don't necessarily trust the mechanic.

And I read in my Haynes manual that for the compression the engine had to be at operating temp, so I'm assuming that the specs you need to go by depend on this. You wouldn't do this test with the engine warm, or do you think it shouldn't matter much?

And what do you mean by having a buddy run the tester? I thought that was just a matter of reading it after you insert it then run the engine a bit

 

[DSM1G90]

what the mechanic told me and to get familiar with diagnosing these issues myself. And I don't necessarily trust the mechanic.

Time to find another mechanic then - he could care less if he helps you out or not with that sort of recommended statements. Remind me not to go to him either...and put a big negative report to him on the BBB service.

..Somebody (if you don't have a remote starter switch handy..) has to hit the key while one holds the compression tool to watch the dial when the needle quits going any higher and you hit the dial lock button the side of the dial case so you can record the reading down for reference.

 

[SLIDER121]

Do a compresson test on each cylinder, if you have bent valves that cylinger will not have compression. Next make sure the cylinder(s) are at top dead center and fill the cylinder with air, if air comes out of the exhaust, the exhaust valves are bent and visa versa for the intake.

You can do the test by yourself if you face the guage to the drivers side and watch it while you turn the motor over.

 

[BogusSVO]

Bent valves is what you have been told, and you want to confirm this.

My questions, like those above have asked.

1) What is the reason for bent valves?
a) Broken time belt
b) stripped teeth on time belt
c) improper install of time belt

2) Is the time belt still installed?
a) yes, then you can run a compression test ( a leak down test would be better tho)
b) No, then you can not perform a a comperssion test

3) If the valves are bent a good amount, a quick check will be to remove the valve cover and see if the cam followers are not in place.


Now that you have made the statement the "My car won't start!"
What is the reason that it will not?
a) no fuel?
b) No spark?
c)Time belt no properly installed ( low/no compression)
d) Bent valves? (low/no compression)

Look at the first pic in this thread, it shows bent valves...

http://www.dsmtuners.com/forums/newbie-forum/341218-how-change-valve-guides-4g63t-head.html

 

[juntjoo]

Time to find another mechanic then - he could care less if he helps you out or not with that sort of recommended statements. Remind me not to go to him either...and put a big negative report to him on the BBB service.

..Somebody (if you don't have a remote starter switch handy..) has to hit the key while one holds the compression tool to watch the dial when the needle quits going any higher and you hit the dial lock button the side of the dial case so you can record the reading down for reference.

You think he prematurely diagnosed me with bent valves? Let me just explain that first he found the belt to be installed with the timing off and when he re-did it still no start then he did the compression test to find no compression. What exactly don't you like about his recommendation? I'll tell you what I didn't like. Over the phone I told him just to leave everything uninstalled before I went to pick up my car since I would have to take it apart anyway, but after I towed the car home I found it all back together. Anyway...

So since as couple of you have asked, the belt was on. I had replaced it myself. First time doing a timing belt job. The old belt didn't snap originally, but it was falling apart. See pic.

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The car could start and run before I took it apart. Apparently I didn't install the belt correctly. I didn't line things up right. And I guess I bent a valve or two or three or four turning the engine over (?). I'm guessing because I didn't hear any abnormal noises. Just the engine turning over after I put it back together. So... That's what happened.

 

[juntjoo]

Do a compresson test on each cylinder, if you have bent valves that cylinger will not have compression. Next make sure the cylinder(s) are at top dead center and fill the cylinder with air, if air comes out of the exhaust, the exhaust valves are bent and visa versa for the intake.

You can do the test by yourself if you face the guage to the drivers side and watch it while you turn the motor over.

Thanks. Yeah, that's what I figured.

 

[juntjoo]

Oh, and no stripped teeth on old belt. But then again as I said the car could start before I took it apart.

 

[juntjoo]

BogusSVO, thanks. I'll have to check for spark. First tho I'll want to verify the compression since I'm giving the mechanic the benefit of the doubt. I have plenty of fuel in there.

 

[BogusSVO]

Whan the mechinic checked the time belt, did he tell you how far off you were?

As of now, the belt is on, and all the time maks line up as they should?

 

[Don Lang]

1 the car was running before you took the freyed belt off, right?
2 you put on new belt and won't start. right?
if 1 and 2 is true, yes you probably missaligned the timming marks and bent your valves.
So put the belt on correctly and see if it starts.
If NO then do a compression cheak, you can do it by yourself, point the guage so you can see it when you crank the motor. The motor does not have to be at operating temp for this. To get a little more accurate readings do it with the motor warm. I don't! because removing plugs on a hot motor is more likely to strip or mess up plug thead holes.
If you have no or low compression I would not waste my time with a leak down test. Time to pull the head. poor water in the ports and see which ones leak. No leaking with water. You could use gas or solvent a little seepage is normal. Just lap those back in, as well as your new valves, if your on a low budget job and can't afford a valve job.
I replaced mine with Stainless steel off eBay. I have good used ones I could sell you. PM me if you need them.

 

[juntjoo]

Whan the mechinic checked the time belt, did he tell you how far off you were?

As of now, the belt is on, and all the time maks line up as they should?

Yeah, he showed me what I did, and pointed out how even tho I put the cam sprocket marks together in the middle, I didn't do it quite perfectly as the dowel pins weren't exactly pointing north. I haven't checked since he corrected it, but I will once I get back in there.

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[juntjoo]

1 the car was running before you took the freyed belt off, right?
2 you put on new belt and won't start. right?
if 1 and 2 is true, yes you probably missaligned the timming marks and bent your valves.
So put the belt on correctly and see if it starts.
If NO then do a compression cheak, you can do it by yourself, point the guage so you can see it when you crank the motor. The motor does not have to be at operating temp for this. To get a little more accurate readings do it with the motor warm. I don't! because removing plugs on a hot motor is more likely to strip or mess up plug thead holes.
If you have no or low compression I would not waste my time with a leak down test. Time to pull the head. poor water in the ports and see which ones leak. No leaking with water. You could use gas or solvent a little seepage is normal. Just lap those back in, as well as your new valves, if your on a low budget job and can't afford a valve job.
I replaced mine with Stainless steel off eBay. I have good used ones I could sell you. PM me if you need them.

Thanks for the offer. I wonder tho if it turns out I have bent valves, if I shouldn't just get a whole new head. I've seen a lot under $300 or a little over that are completely rebuilt and if I were to just get new valves then there would still be a lot of other conditions to check no? Like the valve seats and warpage and so on and so forth. I don't really know but from what I've been reading it looks like it could get complicated.

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[Calan]

...you probably missaligned the timming marks and bent your valves. So put the belt on correctly and see if it starts.

I'll break the mold here and say this isn't the best idea. Trying to start the motor with bent valves will just make more noise and increase the risk of doing more damage.

Crank the motor over by hand to check for any valve to piston contact. And don't...

...do a compression check

For the same reasons as above. If the valves are bent, all a compression test will do is risk damaging the motor further while giving conflicting or confusing results. Instead, do a static leak-down test to check for leakage past the valves. It's safer, and will give you much more accurate results than a compression test will.

 

[DSM1G90]

Gonna throw a dumb one here, yet had this same experience with an EA-82 motor on a Subaru: Bro in law gave me his '89 Subaru that he blew the right side belt on. Now, Suba motors should be non-inteference, but this managed to smack up into No.1 intake valve to bend it.

Took the rocker cover off and the rocker assigned to that bent valve, fell out onto the ground. Now, if OP has bent valves, wouldn't the rockers also be loose since the valves would be stuck down being open giving the clearance to remove the rockers from underneath the cam lobes and hyd lifters?

Why I call doing a visual inspection on all of this .....

 

[Calan]

Now, if OP has bent valves, wouldn't the rockers also be loose since the valves would be stuck down being open giving the clearance to remove the rockers from underneath the cam lobes and hyd lifters?

Why I call doing a visual inspection on all of this .....

Depends on how badly they are bent. If they just kissed the pistons, there may not be much of a visual clue at all, but still bent enough to cause major leakage.

If some are bent to the point that they cracked the guides and are lodged in the head, then there would probably be some pretty obvious clues... like rockers laying next to the cams as you pointed out, and maybe holes in the pistons....not to mention the OP would have to have been deaf to not have heard it when it happened.

 

[juntjoo]

Yeah, I never heard any alarming noises. And thanks again
Calan. I was wondering about how might a compression test further damage things so I WILL go ahead do a leak down test and report back. i'm assuming when you say "static" you're just being redundant right?

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[juntjoo]

Although... If the mechanic indeed reinstalled the timing belt correctly there shouldn't be any further risk of hitting the cams no?

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[DSM1G90]

...and "IF" is the keyword here since you prob didn't see the install - just relied on his talents as a mechanic to do the job right.

AND... If you didn't hear anything, then wonder if the mechanic's install just wasn't done correctly and the belt just did a nice hop just to throw off valve timing where it killed the compression, but not to incur valve damage...

And, the first visual would to be to pull the cam sprocket cover off the top and get the pulley mark on the TDC on the lower cover...and see where the timing marks are on the cams in relationship with the TDC mark on the crank pulley.

The first time may not be correct since the cam marks prob be off 180*, but roll the pulley around another full turn, stop at TDC and see what the marks on the cams are looking like.

You might find your answer this way. - good luck -- DSM