Hi Guys,
2007 Honda Accord V6 3.0L J30A engine. 250,000km (155,000 miles).

While underway, camshaft position sensor (CMP) activated CEL and VSA light. A few hundred yards later, after a little acceleration, the engine stopped. Engine would turnover on key but wouldn't start ie not even a hint of kicking into life. After shipping vehicle back home, pulled off the camshaft covers and discovered cambelt was broken. Subsequent investigation into why the cambelt had broken determined the tensioner pully bolt which goes into the water pump housing was a couple of turns loose, enough to allow the belt to become misaligned on the tensioner and the rear cam sprocket such that it was scraping along the sprocket rear plate. But the main damage to the belt was being done as it passed the tensioner with a quarter of the belt hanging off. The remains of the belt showed a continuous stress line which weakened the belt longitudinally. It stretched, (CMP activates CEL) then shredded into two pieces (engine stops).

The J30A is an interference engine and on this basis it was felt the engine had most likely suffered significant damage. The only question was if it was economic to repair given the age and mileage of the vehicle.

Initial examination involved placing an inspection camera down the plug holes. No piston damage or even scarring could be seen on any cylinder. Caution prevailed however because the angle of the spark plug opening only allowed the camera to see about a third of the cylinder and of course the valves could not be seen.

The engine was barred over to TDC. No contact was made with any valves. An old timing belt was then installed and timing reset. A leak down test was then conducted with each cylinder barred over to TDC compression. This was done several times and the timing marks check for accuracy after each set of six had been checked. Leak down values were consistent on all cylinders except No 3. There were no bubbles in the radiator or header tank and no leaking through the oil filler opening suggesting the head gaskets were good and the valve seals were ok. There was no leaking from the exhausts on any of the cylinders and so the exhaust valves were tight. While all cylinders had some minor leakage through the throttle body, no 3 was excessively so and stood out as being an issue that needed further investigation. The likely cause for this would be a leaking inlet valve/s which might be caused by a burnt valve or a bent valve. Burnt valves are more likely on exhaust valves than intake valves and given the event which precipitated this investigation it was not unreasonable to assume at that least one cylinder had suffered some mechanical damage and that No 3 probably had one or two bent intake valves.

Out of an abundance of caution, both heads were removed for inspection but No 3 cylinder on the rear head was the primary target.

Once the heads were removed it was determined that the pistons and chambers showed no scarring or damage, no broken bits of metal and were generally in good condition. Similarly, on the head, all valves were fully closed with no witness marks suggesting contact with the pistons. Given the observed leaking through the throttle body from the No3 cylinder, and the expectation of bent valves, this was an unexpected outcome.

Both inlet valves were then removed from the No 3 cylinder and the stems rolled on flat surface to check for stem straightness. Valve heads and valve seats on the cylinder were checked for burns, deposits, hot spots etc. Valve guides appeared tight and the apertures for the valve stems were circular (not oval). Springs and valve keeps were checked. No faults could be found.

In summary, the cambelt broke and being an interference engine, the expectation was that some damage to the engine must have occurred. A leak down test identified an excessive leak from No 3 Cylinder yet valves from this cylinder and every other cylinder are all straight. No physical damage appears to have been done.

So, to the title of the post. If the engine is not damaged then, why am I getting leaking through my inlet valves on No 3 cylinder?

Thanks in advance .

Terry

 

If the cylinder heads are off the car, then turn them upside-down with the cams out and valves/springs installed. Fill each bowl (top of the cylinder) with water. Look to see if water is leaking out of the #3 cylinder over time. The valves can't be sealing for some reason.

 

Thanks PA Honda,

Unfortunately I have removed all the valves at this point and don't want to go through the process of reinstalling them unless it is a final install. So I have googled the test you alerted me to and I think I will do it after I have lapped the valves as a final test before I put the heads back on the block.

Thanks again PAHonda

Cheers

Terry

 

Hi Guys,

Thought I would follow up on this one to close it off. Recapping, you will recall I could not actually find anything wrong with the engine despite a cambelt failure and this being an interference engine. However, on strip down I did see some small witness marks on the edge of the exhaust valves on Cyl's 3 and 6 which happens to be in firing order. I rolled all the valves on a flat table edge to see if I could see any indication of bent valves but to no avail. So I thought maybe these marks had simply occurred when I barred the engine over carefully without a cambelt on. They all appeared straight and moved within the valve guides without restriction. So I decided to do a valve grind valve since I was there and because all the valves showed signs of carbon deposits on their faces and seats which probably explained some of the mild leaking during the leak down test. Before I did this I did the water test that @PAhonda suggested. Quite a number of the valves were leaking water at first but after the valve grind had removed most of the built up deposits, that resolved most of the leaking. It was during this valve grind that I found two exhaust valves on Cyl 3 and one exhaust valve on Cyl 6 (which matched the firing order) would not grind evenly. That is to say I could not grind the entire face of the valves suggesting they weren't sitting flush on their valve seats. I then tried slowly revolving each of these suspect valves on their seats with my finger and it became clear that these valves were taking an elliptical path around the valve seat rather than circular. Failure to grind evenly and an elliptical path on revolving these valves on their seats pretty well identified these three valves as bent. So, while I didn't become a legend for dropping a cambelt in an interference engine without damaging it, I certainly got away extremely lightly with just a few valves to change out. After changing the valves for new and further grinding them into their seats I completed another water test and everything was tight on both heads. I had the heads professionally skimmed and reassembled the engine.

It is difficult to start turn the key after all this work. I kept thinking I must have forgotten something or got something wrong. But when I pluck up the courage, the engine started first time and ran smoothly and quietly. Some codes to reset and she was ready for the road again. I have run her now for several thousand kilometres and the engine feels like it's new. I guess the valve grind, head skim and necessary valve adjustment would have contributed to improving the all compressions and timing so that not only does it run better, it is more fuel efficient.

I love this engine and I love the car. Honda's J30 is tough and from my experience the engines just keep going if the are maintained properly and you don't have unexpected cam belt failures! I was lucky this time but this engine has probably got another 200K in it!. My wife needed another car so our intention was to sell this car once it is back on the road. But I will never get out of the car what I put into it and she really is great runner now, so I figure I may keep her for a bit longer.

I think I did a really good job. Everyone said so...LOL. I know, I sound like Trump. But for all you guys out there if you take your time with these things not only can we get our prized possessions back on the road we can avoid the waste that comes from sending an otherwise perfectly good car to the recycling yard simply because of a slightly bent valve or two. That does help save the planet.

Anyway, here are some pictures that unfortunately I couldn't get in the right order no matter how hard I tried so they are a bit scrambled but I have captioned them which may help.

About to start the valve reassembly on one of the heads. Everything was so clean I was happy to lay my biscuit on the table with the coffee!! It was actually quite a calming experience.
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The cylinders came up nice. Did someone say a cambelt had broken?

Both banks completed and ready for the heads to go on after they are worked on.

An initial water test. Most of the valves leaked or seeped because of all the carbon deposits on the faces and seats.

The valve grind. First time for me but wasn't as hard as I thought it would be.

The heads skimmed and cleaned out, and the valve seats with nice little glints from the polishing.

Ready for the valve gear to be reinstalled. These heads looked brand new!!!

This was as difficult as I thought it would be. just take your time, don't rush and inspect your work closely.

The heads all skimmed, cleaned of contamination and with the valve seats glinting in the light after being polished.

The valve trains reassembled, cam sprockets and lower intake manifolds fitted. Ready to be reacquainted with the block!!

The rear bank with head gasket fitted waiting for the head to be lifted on to it. I did this on my own and I'm 67 so it was a tad tricky since I had to get in the engine bay and kneel on the engine to get in the right position. Remember the vehicle is jacked up to so it's high.

Valves adjusted and looking sweet. I love this engine.

Finished!

When you do a job like this, the pride you take in the car is immense. Why would I want to sell this after I put my heart in sole into saving her from the scrap yard? Nah. She's a keeper.


Forlorn. I towed her home thinking the car would become scrap value only and I was actually quite upset at the thought.

It was a mess when we exposed the cam belt which was broken in several places and had teeth stripped off it.

An inspection camera through the sparkplug holes only gave a limited view but all cylinders looked like this and gave me a feeling that there might still be hope.

With the heads off I was surprised at the cleanliness of the cylinders. This is 250,000km's! Those deposits were flakey and generally pretty easy to remove. The cylinders showed no sign of damage.

The valves all looked like this and again no damage was indicated.

The clean up begins and a bit of CRC and some rubbing was all that was needed to get these cylinders looking good.