Gerinski

Hi, I'm having a serious engine problem and neither me nor my mechanic can figure out what's really causing it, I'm hoping that someone here can help. I have done some searching and I have found a couple of possibly related threads but none speaking about a problem as serious as mine. I'm posting the links at the end.

Some background. I'm Spanish, living in Spain. My car is a 2006 AP2 imported from the US to Europe by a Belgian guy in 2011. He buys cars in the US and sells them in Europe. He told me he bought the S initially for himself, drove it for 3 years and in 2014 he put it for sale. I was living in Belgium at the time and purchased the car with 60k miles. The car looked completely stock and it drove nicely.

After only some 1,300 miles I got the CEL light on, checked and it gave a bit low compression in 2 cylinders. Apparently the exhaust valves clearance was a bit too tight and they got burnt. They replaced all the exhaust valves, as far as I know no shaving of the head was done, and back on the road. In the meantime I decided to move back to Spain so I took the car and drove it from Belgium to Spain. After some 500 miles of trip I tried some high-speed-high-revving cruising on the highway (around 135 mph for some 5 minutes) and suddenly the engine blew up, I lost all the engine oil. Tow the car to Spain.

What we found when we opened was:
- the camchain arm and guide broken in pieces all over the place
- the check valve bolt of the Timing Chain Tensioner (TCT) was found in the oil pan (together with a valve retainer which must have fallen during the head service, but no retainer was missing in the valves, so that was no big deal).
- the cam chain had been eroding the chain cover (see the area marked with the red circle) until it perforated it losing all the engine oil.








Our first diagnose was that when re-assembling the cylinder head they must have mounted something wrong in the TCT / timing chain set-up, resulting in tensioner failure and the chain turning at high speed without tension and grinding the cover down until perforation.

OK, bad luck, the car was now in Spain and the workshop who did the head in Belgium didn't want to take any responsibility. Since the engine oil was full of aluminum flakes and particles everywhere I took the car to the biggest Honda Dealer in Spain, in my hometown Barcelona. They disassembled the whole engine part by part, including the cylinder head, valvetrain etc again to make sure everything would be cleaned up and correctly reassembled.
Incidentally, I don't know if this may be of importance, they found out that the car is fitted with Toda Racing camshafts and adjustable timing cam gears and valve springs. The guy who had bought the car in the US didn't even know it, but apparently everything had been fitted properly, including some mod which needs to be done on some rocker arms.

Taking the occasion of complete engine disassembly they replaced all the crankshaft and conrod bearings, the complete timing chain kit with the sprockets and guides and of course a new TCT, checked the whole cylinder head assembly, VTEC system, new clutch... you could say I had a new engine from that moment (everything OEM except retaining the Toda camshafts & parts). They assembled everything back and I picked the car up.

Now if that breakdown was bad news and some 7,000 € less in my bank account, now come the REALLY BAD news!

I did the first 400 miles or so very calm and gently so as to run everything in. Car ran fine, oil level was perfect, not one drop consumption. Then I said to myself, ok it's time to start pushing it a bit more, so I went for a twisty mountain road and did some only 35 miles revving it up and shifting around 7,000 - 7,500 rpm. Suddenly the engine shuts down, as if it ran out of fuel or ignition... I press the clutch and after a couple of seconds de-clutch again and the engine re-starts, I got frightened and continued really slow trying to get to the next village, but after a couple of miles the engine finally stalls and I have to call the tow-truck again, back to the Barcelona Honda Dealer.

They open the head cover, cam chain cover, oil pan and... what do they find?

- the TCT oil check valve bolt is found again in the oil pan (it was a brand new OEM TCT)

- the cam chain had started again grinding the cam chain cover at exactly the same spot as before, at the side of the fixed cam chain guide. Luckily this time the engine stalled before complete cover perforation.

- the cam chain guide shows signs of having been touching the cam chain cover, it looks worn out, the plastic looks worn out in the area marked with the red circle. This means that at high rpm the chain and guide at that point must have freeplay both towards the left (so as to wear out the solid aluminum "bulge" of the cover (where a bolt goes through) as well as axial freeplay (to the front of the car, so as to wear out the inner side of the chain cover as well as the outer side of the guide plastic).

- the cam chain slack must have gotten so bad that the timing chain was displaced by 3 teeth on it's crankshaft sprocket !!! Luckily because of this the engine stalled before doing any more damage and perforating the cover again.







The engine was carefully assembled by the chief mechanic of the Honda Dealership. He can not figure out what is wrong in order for exactly the same problem to reproduce after having replaced the complete timing chain kit, TCT, guides, cover....

He also tells me that he has seen many cases of TCT failure but never that it caused such grinding of the chain cover by the chain rotation. He says that at most TCT failure, even the check valve bolt becoming loose, will cause the well-know rattling noise but nothing else, at the very worst the ECU going into "safe go home mode", but never such a serious problem as the chain eating the cover up.


Any thoughts will be very appreciated!!!

Lack of oil pressure to the TCT? (oil level was perfect, oil pump apparently ok...). A faulty brand new TCT seems to be out of question since the previous TCT caused the same problem.

If I should believe the Belgian guy who sold the car to me, he had been driving it for 3 years, maybe some 10k miles, without any problems (of course with the Toda parts he was not aware of). So it's only since I got the cylinder head serviced that the problem has happened, but it has happened twice exactly the same after complete disassembly and rebuilding of the engine.


Thanks guys !

EDIT: Oeps, I forgot the links to possibly related threads:

https://www.s2ki.com/s2000/topic/806...#entry19214950

https://www.s2ki.com/s2000/topic/768...hing-came-out/

https://www.s2ki.com/s2000/topic/453...ain-tensioner/

cosmomiller

I think everyone is waiting for Billman to chime in.

Billman250

I would inspect both the keeper and the check valve. If either made it's way into the chain while the engine was running, it will do major damage (busted guide). All keepers should have been accounted for during the valve job.

Something would have to walk forward to saw at the timing cover like that. Check the installation/positioning of the camwheel, and the crank pulley. Something is missing or being overlooked.

While the TCT valve falling out twice is odd, it is not the underlying cause unless it got itself caught in the chain.

Gerinski

Thanks Billman! may I ask you a couple of questions for my better understanding of the subject:

- that valve keeper was found only in the first repair, so it's surely not the cause of the problem now. All the keepers were in place and they are again. I suspect that one fell without getting noticed the first time they replaced the exhaust valves, they might think they just lost one and take a new one when servicing the head (or maybe it had been in the oil pan even from before).

- if the TCT valve bolt gets loose and falls down to the oil pan, assuming it doesn't get caught in the chain, would that be cause for insufficient oil pressure at the TCT and therefore insufficient chain tension so bad as to causing that sort of damage on the cover? or would it just cause some rattling noise but never this kind of damage if everything else is in order?

- somewhere I have read that the valve bolt should not be tightened very hard, others saying to tighten it hard, others to leave it just flush and punch it in order to block it, others to be careful that the holes on the bolt and the TCT body remain aligned, others that it doesn't matter, others to apply bolt loctite, others to not to... I'm confused. How should the valve bolt be tightened? punched or not?

- could it be an oil pump problem? or some oil passage blocked? the sawing of the timing cover must have produced quite some aluminum debris, in principle they cleaned it all but perhaps some internal oil passage feeding the TCT remained obstructed? I find it very strange that a brand new TCT failed.

- if the TCT does not function properly due to insufficient oil pressure, the chain has slack so its arm bumps into the TCT piston causing rattling, I'm assuming it's that vibration which is causing the valve bolt to get loose until falling down. Could you agree?

- this last time the chain was indeed out of timing by 3 teeth, so I assume that this was indeed caused by the valve bolt getting caught in the chain before falling to the pan. But the fact is that the bolt got loose because of something.

- the cam sprocket in the camshaft and the camwheel in the head look properly mounted, it's actually quite hard to mount them wrongly. I also wonder how can the chain move forward so much as to saw the cover, even if it has significant slack due to insufficient TCT function... of course we will re-check the sprockets mounting.

So far my best guess is:

1. the oil pressure reaching the TCT is insufficient. The cause being an obstructed oil passage or an oil pump failure.
2. at high rpm the TCT function is insufficient, causing the chain arm to rattle against the TCT piston. This vibration causes the valve bolt to loosen until falling down.
3. the insufficient tension of the chain at high rpm causes the chain to have axial motion sawing the inner side of the cover.

Would you find this diagnose reasonable or some weak point in it? points 1 and 2 seem reasonable to me but I'm still puzzled that everything else being OK, the chain slack can be so bad as to saw the cover as it does. It seems indeed that that kind of forward motion of the chain might have a separate root cause in the alignment of the sprockets at camshaft and camwheel, but I can not see how can that be possible when it has been disassembled and reassembled 2 times.

Thanks in advance!

Billman250

The TCT relief valve must be TIGHT. If not, it will back out.

I can crank it down without any punch marks or loctite. If you are unsure, clean both parts with brake clean and compressed air, and use loctite. Using a screwdriver with hex bit on the end, crank that thing down tight. It can withstand a good bit of torque. If you're short, loctite will take care of it.

The orientation of the hole in the TCT valve and hole in the TCT body does not matter. It can be aligned or not, that has no affect on it's operation.

I have seen cases where the valve backed out and fell into the pan, and the customer didn't even know. No symptoms.

It's important to start from the beginning. You had no chain problems until after the build. Your problem lies beyond the TCT, even a TCT with no oil pressure will not cause that much chain slack.

Was the head milled, if so how much?

No S2000 cylinder head that is removed for valve work should ever be milled.

Be sure the TCT was operating as it should (worm gear is free) and all internal parts are accounted for.

james0933

Boy, is honda going to warranty the work?

Gerinski

Warranty? It's a 2006 american car with 65k miles breaking down in Spain in 2016...

Billman thanks a lot for you comments, they will surely be of great help. As far as I know the head was not milled, at least not since I own the car (they would have charged for it in the invoice!). But it's a good clue, we will check the head depth to see if it was ever milled.

Gerinski

One more thing, the dealer was doubtful about the Toda camshafts, they said "after all they are the only non-OEM parts in the engine, everything else is pure stock and most of the important components brand new or checked and OK, so it's the only thing we can guess as possibly causing some problem". I'm not convinced at all.

Could camshafts and/or their gears in any way be the cause of the problem? The camwheel driving the camshafts I believe is stock, Toda does not supply it with the cam shafts or gears, so I don't think that can be the cause.

These are they:

My link

My link

Gerinski

Sorry for many questions but I keep squeezing my brains in search for possible causes.

Is there any way of measuring if the chain slack is normal with the timing cover out? (either with the tensioner out or mounted, whichever).

james0933

The work and parts they did to repair your s2000 originally carry a warranty regardless of the model year and mileageof your vehicle at the time.