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#948294 - 11/25/15 07:02 PM Leakdown test results and potential bent valves  
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OoPEZoO Offline
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Amish Country, PA
Any engine gurus around here? I've done plenty of things mechanically, but I need a 2nd opinion on a car engine.

Long story, short....our old beater Corolla died on the highway last week (after 250k trouble free miles). Upon investigation, I found two teeth chipped off of the crank sprocket for the timing chain, and the intake cam sprocket is so worn that the chain was skipping on it when rotating the engine by hand. The exhaust cam appeared to still be in time with the crank, but obviously the intake cam was WAY out.

My big concern was the valve train was completely trashed as everything I have read tells me that it is an interference engine. So today I investigated things further. I very slowly worked my way through rotating the crank and cams independently so I could get each cylinder's valves to close and perform a leak down test. All four cylinders came back between 15-20%, and that was stone cold as I can't warm up the motor. Those numbers should theoretically be better on a warm engine. That's great news if it's accurate, and I don't see any reason why it isn't. Is there anything I am overlooking here, or does it appear that the valves are not bent and I might have gotten off easy?

Instead of buying a used motor to swap in, I might be able to get away with new timing parts and a water pump. Can anyone with more engine experience confirm or poo poo on my thought process?


-Keith (Yup, thats me...and my rubber chicken)

Making the world a better place, one rubber chicken at a time!

'98 Buell S1 Lightning
'06 R1200GS
'86 Honda CB125
'00 R1100RT (parting out, PM me)
#948307 - 11/25/15 11:02 PM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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blackbrick Offline
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20% leakdown is close to bad. When doing the test, listen for where the leak is. Stick your ear in the exhaust pipe. If you can hear the air, it is exhaust valve. Listen to the intake...intake valve. Pull dipstick out and listen. Piston rings.


Marshall
92 K75s schwartz
94 K75s schwartz
09 K1300s lava orange
#948315 - 11/26/15 12:28 AM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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OoPEZoO Offline
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I think it's definitely leaking past the pistons.....which isn't surprising considering the motor has 250k miles on it. I swiped my Wife's stethoscope, pulled the end off, and stuck it down next to one of the oil passages right above the crank pulley. It sounds like a wind tunnel. I couldn't hear anything from the intake or the exhaust.

The other thing I did since my original post was rotated the crank to get the piston I was working with to TDC. Previously, I just had all 4 Pistons somewhere in the middle of their travel. It's a bit of a bear to deal with both cams and the crank at the same time since the chain is removed. It made a noticeable difference in the readings. The cylinder I was working on went from previously being 15-20% leakage, to 10-15%, and was very repeatable.

I'm also thinking those numbers would be better yet if the motor was up to normal running temperature, but that is impossible in its current state of disrepair. I think I'm going to back through it tomorrow and recheck each cylinder with its piston up where it should be.

Last edited by OoPEZoO; 11/26/15 12:30 AM.

-Keith (Yup, thats me...and my rubber chicken)

Making the world a better place, one rubber chicken at a time!

'98 Buell S1 Lightning
'06 R1200GS
'86 Honda CB125
'00 R1100RT (parting out, PM me)
#948318 - 11/26/15 12:37 AM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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blackbrick Offline
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each piston must be at tdc and all valves on that cyl closed for valid testing.

Last edited by blackbrick; 11/26/15 12:39 AM.

Marshall
92 K75s schwartz
94 K75s schwartz
09 K1300s lava orange
#948320 - 11/26/15 12:52 AM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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OoPEZoO Offline
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Any idea how difficult that is on an interference engine with the timing chain is laying on the garage floor.... grin

Seriously though, do you at least think my thought process is correct that if everything checks out with the leak down test, my valves are most likely ok? It makes sense to me, but I don't have enough hands on experience diagnosing internal engine issues to just claim it a victory.


-Keith (Yup, thats me...and my rubber chicken)

Making the world a better place, one rubber chicken at a time!

'98 Buell S1 Lightning
'06 R1200GS
'86 Honda CB125
'00 R1100RT (parting out, PM me)
#948321 - 11/26/15 01:17 AM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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Keith...the only way to really know is to borescope. A leak down test isn't a test of the integrity of the valve, only the integrity of the sealing of that valve.. Many things can cause a valve to leak such as carbon build up, valve seat wear, partial deterioration of the valve itself. It use to be the standard in checking air cooled airplane engines, but is not even an approved method for annual inspection anymore. I've listed a couple of things below for you to read... I realize different than Toyota, but not than much; principals are the same.

http://www.tcmlink.com/pdf2/sb03-3.pdf


http://www.avweb.com/news/savvyaviator/188758-1.html


David
RT WET
#948328 - 11/26/15 02:19 AM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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OoPEZoO Offline
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Amish Country, PA
That's some good reading. Thank you

Let me also throw this out there......my #1 goal is to get this thing back on the road for as little $$$ and effort as possible. It is our "beater" car that I use for commuting 600 highway miles a week. I'll swap in a used motor if it is necessary, but if I can throw $200 and an afternoons worth of work at it and get another 3-6 months out of it......I'll be thrilled.


-Keith (Yup, thats me...and my rubber chicken)

Making the world a better place, one rubber chicken at a time!

'98 Buell S1 Lightning
'06 R1200GS
'86 Honda CB125
'00 R1100RT (parting out, PM me)
#948335 - 11/26/15 03:49 AM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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Pull the head Amigo. All else is just a crapshoot.

MB>


74 R90S
98 K1200RS
03 1150RT
04 DRZ400
15 1200RTW

......and a Jeep Rubicon

BMWMOA, ABC.
IBEW 332
#948344 - 11/26/15 08:12 AM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  

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Hard to tell. 15-20% on a Japanese four cylinder engine from that time frame is not exactly encouraging, even when cold.
Now: if the car was using oil before it stopped working those numbers are probably due to acceptable (for the mileage) tear and wear, most likely valve seals and perhaps one or two piston segments.
But... to tell a bent valve the head needs to come off. There aren't many alternatives. At least on contemporary Honda engines that's the only way to tell if you have one or more bent valves.

At that point, given the amount of labor involved for an unknown result, a new engine makes a whole lot more sense.

#948349 - 11/26/15 12:32 PM Re: Leakdown test results and potential bent valves [Re: OoPEZoO]  
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I always enjoy following these technical threads BUT, I can't help myself, I just have to ask - after reading "I swiped my Wife's stethoscope...) is this why the poor woman is slamming the toile seats? rofl wave

Looking forward to reading the resolution of the motor issue.


Paul
“Stay where you’re to till we comes where you’re at “

00 R1100RT
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