the_morbidus

I have a 2000 Honda S2000, with ~165k km.
Recently, I have had trouble starting it, it tries to turn over but struggles, and when it starts, it runs fine.
No misfire codes, nothing, drives well, and even accelerates well.
The only code I get occasionally is a P0373 which is Crank position error.

I did a compression test, and these are the results:
Cylinders
#1 - 222 psi
#2 - 218 psi
#3 - 178 - 180 psi ( I tested this cylinder a couple of times )
#4 - 226 psi

So cylinder 3 is the culprit with bad rings, I assume this because it is also burning through oil faster than it used too. Usually it goes through half a litre every 2-3k km, but this time it was down 2 litres.

Is it possible to repair cylinder 3 with simply honing the cylinder and replacing the rings with new ones? Of course I would be doing this to all 4 cylinders, my question is more, do I need to send the block to a machine shop? Or can I get away with just replacing the rings?

I have always known cylinder 3 had an issue. When I bought the car in 2009, it was the cheapest one in the market at the time because it had a series of issues, mainly that the valve seals were burned and it needed a serious valve lash adjustment. After getting the head back from the machine shop and putting everything together, I did a compression test and the results were these:
Cylinders: (this was 14 years ago so I don't remember the exact numbers, except #3)
#1 - 225 psi
#2 - 222 psi
#3 - 205 psi (it jumped to 210-212 psi after adding a few drops of oil)
#4 - 228 psi
But the car started, ran well, passed emissions, and cylinder 3 was within 10% of the rest so I decided not to replace the rings back then. It had 116.7k km, was fairly healthy. For years it never gave me an issue, aside from having the noise from the chain, took care of that with a ballade sports chain tensioner a few years ago, replaced the injectors due to them leaking and causing a weird idle.
But last year I decided to go to the track for the first time with this car, first time pushing it, really enjoyed the time I had at Toronto Motorsport Park that I returned back 3 more times. Guess the engine didn't appreciate it, despite me making sure it always had fresh oil and it was topped up before entering the track. This year I installed a Radium fuel rail with a pressure gauge, first thing I noticed was the low psi when turning the key on, it explained why sometimes, lately, I didn't hear the pump very well. So I replaced the pump with an oem replacement from Delphi and pressure is back at 45-48 psi with about 40-42 psi while cranking.

Another question is regarding the chain, is it possible to get away with just replacing the chain? Or should I replace the sprockets?

I'm going to buy a thin scope to peek inside cylinder 3 and see the condition of the walls, I really hope there is no scarring.

Chuck S

Down 2 litres (sic) is still on the dipstick? Does this happen in normal driving? You need to check the oil level more often -- but you've figured this out already! There are claims that some motor oils like Mobil-1 full synthetic "burn" more easily than others. Whatcha using?

Good luck. Engine rebuilds have a dismal success rate. Ballade timing chain tensioners are known to overtighten (and consequently stretch) the chain. Low pressure could easily be the valve seals or a burned exhaust valve like a few years ago. Valve adjustment is spec? Recommendation is to set to loosest end of the spec as they tighten in use.

-- Chuck

the_morbidus

Hey Chuck!!
About the engine oil, I just use 10w30 Castrol GTX. I think at some point I did try to use synthetic, and I think I was using Castrol Edge, but because I was driving the car so little, I switched back to just regular oil. I think it was 2016 when I changed to synthetic, then in 2018 I bought a motorcycle and I might have put 3 to 4 k km that year on the S2k, and just went back to regular because I thought I was just wasting money on the synthetic, for the short intervals between oil changes. I usually change the oil and filter every 2k km.

About how low the oil got on the dipstick, when I pulled it, the oil line was between the tip of the dipstick and the /minimum/low oil line, so I dumped in 1 L expecting to see the new oil mark somewhere between low and full, yet the line was right at low, that was when I realised I ****ed up..... , I dumped another litre and the engine still would not start. I assumed I flooded the engine with all the cranking, so I let it sit for a few hours and came back later and got it running.
This was at the end of March, about 3 weeks ago.

Last oil change I did was middle of October, just before the last time I went to the track. Also, I want to be clear I did not abuse the car at the track, not for the lack of trying. I discovered I get motion sick very fast, I barely last 5 laps before I have to exit the track and try not to vomit everywhere. So about 6 minutes in the track, and then 25 minutes out trying to cool off. I run the 1st two laps about 50% to warm up the tires, then I push the other two, then I'm out.

Anyways, despite the very mild winter, I didn't drive very much after the track day, so I assumed the oil was still alright, it was a lot of short drives about 3 to 10 km, and a handful of longer ones, but doubt it was more than 1500 km since the oil change. A regular winter has me parking the S2K beginning to mid November and then taking it back out in mid March, this winter I drove through November, some days in December, maybe 4 or 5 days in January, was parked in February and started taking it back out mid March.

About the Valve adjustment, I have only done it twice, I did it back in 2009 with 116.7k km and I did it again in 2014 or 2015 with about 135k km. I did purchase a valve cover gasket kit a couple of months ago, was planning on doing it next month. But yeah, I don't know their condition, maybe it is worth to check it.

When I replace the chain, I'm definitely going back to the factory chain tensioner, or do you have an alternative recommendation?

Lastly, a buddy of mine is suggesting I do a K24 swap. The extra torque is tempting, but I have a Haltech Platinum Pro and if the harness needs to be replaced, it would suck to get another ECU.

Edit: I forgot to mention that I have an aftermarket oil cooler installed, that has added an extra 1 L capacity to the F20C's 5.5L oil capacity to a total of 6.5L, so when I was down 2 L, I still had 4.5L flowing around.
I modified the car with an oil cooler and a larger aluminum radiator to try to keep the engine at decent temperatures while at the track.

dagle

do a wet compression test or a leakdown to confirm it's the rings. with cylinder#3 in BDC (bottom position of stroke), you could sneak a little camera down the spark plug tube to inspect the status of the cylinder walls. it'll tell you if rering-ing is an option (also, make sure you get AP2 piston rings not AP1).

Possible scenarios and available options:
- no scoring present -- you are clear to re-ring and reassemble (while the engine is apart, do the rod, main and thrust bearings too)
- scoring is present -- requires disassembly to measure depth of scoring (or feel if it'll catch a fingernail.) if it does catch a fingernail AND it runs the entirety of the bore, you will need to run oversized or sleeves.

If you can hone less than 0.001" to produce cross hatches uniformly that'd be ideal, but for stock power levels and heat i personally don't think it's a huge deal either way.

Slowcrash_101

I can almost guarantee it's not a cylinder issue but rather a burned valve. You can check it by removing the exhaust manifold and looking at the valves on cylinder 3. If the valve is burned it will look different than the others, more beige and ashy. Tight valves lead to burned valves which lead to worn guides which leads to worn seats. The worn valve guides allow more oil to seep through which explains the increased oil consumption.

Jub

Do a leakdown test to find out where the compression is going. Listening to where the air is going should tell you if you're leaking down that much. Likely either rings or head. If it's rings, it'll come through the crankcase. You can take off the oil cap and listen. If it's exhaust valves, air will leak out of the exhaust. I had a burnt valve last year and my pic is below. You'd be able to see the ashy valve stem by looking through the exhaust manifold port. I'd suggest finding someone who has done a bunch of these heads before refresh it. I did hear that our seats are difficult and I don't think you can actually buy a new Honda seat. Usually they can re-shape the old one but if this is round #2 for yours, you may not have enough material left. I had InlinePro do mine and it's been good for the last year. Got me all my compression back.

Attachment 140712

Ever since it happened to me, I feel like I've seen more of them all over. It's believed to be more frequent in 06+ cars but I think more people have it than they realize. Mine was definitely bad for over a year and it only threw a CEL twice, both of which were autocross test and tune events where the car had a lot of runs back-to-back. Both times, I cleared the code and ran it. I was still pretty quick. It ran pretty fine though, in hindsight, there were some signs. Cylinder 4, where that valve is, was leaking 80% of its compression. The shop I drove it to thought it was behaving fine and was very surprised to find that they'd be removing the head.

the_morbidus

Sorry for the late reply, wanted to do a couple of tests before replying.

So I did a wet compression test, I dropped into each cylinder an amount of oil that is more than a tea spoon but less than a table spoon worth of oil. Not sure if that was too much or too little.

There was a bump on the compression numbers but not a lot, so I guess I can rule out Piston Rings. I think @Slowcrash_101 is correct, it's probably the valves.



Compression test


So, I got a small camera off amazon that connects to my phone and I peeked inside cylinder 3, and while the light on the camera was kinda weak, with piston at bottom dead centre, I can definitely say the cylinder walls are pretty clean and shinny. Also, no marks on the piston head. I did the same thing on cylinder 2 since it's a companion cylinder and can say that its walls look the same as cylinder 3, and cylinder 2 is a healthy cylinder.

After that, I undid the exhaust manifold and took a few photos, not great photos, also there is a lot of carbon buildup, probably from all the short drives I make.

Cylinder 1





Cylinder 2





Cylinder 3





Cylinder 4





I know, I know, they look terrible, and I really could not tell anything from the photos since I don't know how to read valves.
I decided to go to a friend's shop and borrow his Leak Down Test and his shop line.
I made sure it was at TDC during compression stroke.
I got 26% leak on cylinder 3, so low leak, on the green, which is good.
While checking for hisses, no bubbles coming from the radiator which is excellent.
I undid a vacuum line going to the intake manifold but I felt no pressure on my finger when I plugged the hose with it, maybe the throttle plate does not fully close?
It seemed like I could hear a hiss coming from the air filter but I was not sure since the Leak Down Tool was sitting beside it.
I did hear a low hiss coming from the tail pipe.
Since I'm barely 5'6", I could not lean over and reach the oil filler cap with my ear to see if I could hear anything from there.
I also did it outside near a somewhat busy road so the traffic noise was not helping. Maybe this leak down test was a failure, because of my first time doing it and well, incompetence.

I will try to tomorrow check for valve gap, it could be as you guys pointed out, there might be very little to no clearance. That was one of the original issues when I bought the car back in 2009.
Before I sent the head out back then, I did a valve gap check and there was no gap in the intake side of cylinder 1, and no gap on the exhaust side of cylinder 3. So maybe this problem is back again on cylinder 3.

I'll update you guys on wednesday.

windhund116

Hiss from exhaust pipe could be burnt exhaust valve(s). Number 4 looks like exhaust stem may have gotten a little cooked.

Jub

When you run the engine with little to no valve clearance on the exhaust side, the valves do not cool off sufficiently. They cool off by transferring heat to the valve seats when they're closed. Diminishing clearances provide them a smaller amount of time to cool in each cycle. When clearance gets to zero, there's no cooling and exhaust gases start passing them and heating up the seats behind the valves, causing the seat material to be more brittle and the valves to recede quicker. The whole issue exponentiates itself which is why it's important to keep on top of adjustments.

I had mine adjusted 3 times in 24k miles before I finally found my burnt valve. To my knowledge, only on the second adjustment in that window were the exhausts noted to be tight. On the third adjustment, they were still in spec. The damage was already done. If yours are in spec and gas is getting by the valve, that indicates the valve is not sealing due to the seat/valve contact being no good. Based on your car's history, this would be my bet.

I don't have enough experience with this to judge by your stems. Cylinder 4 looks obviously burnt to me but maybe they're all ashy and I just don't know it. Would hope someone more knowledgeable would chime in on the looks of them. It would definitely be worth it to try to re-do a leakdown in a quiet environment. You can also use a balloon over orifices to figure out where it's going. Put a balloon over your exhaust and see if it fills up. Idk how easy it is to tell but I've heard it works and it makes sense.

the_morbidus

Update:

So I did the valve lash adjustment, here are the results.



So, the numbers inside the box are the gaps I found, the numbers outside the box are the new gap measurements. They were all basically too tight, especially cylinder #3, of the two exhaust valves, the one closer to the front, initially I thought it had no gap because I kept trying to measure it and after getting down to 0.005, I realised it the rocker or whatever it is called, was just down. Reason I had to do a correction there.

So, trying to remember what I did back in my last valve measurement, I am not 100% sure, but I might have adjusted them on the tighter side. I did not realise that the valves and the valve seat would wear with time and so the valve would slowly over time move up and close the gap. So I think I created my own problem. It's a learning experience, and this time I set it a bit looser.

So the adjustment was last night.

This morning I went grocery shopping and drove the car for 40 minutes, upon getting home, I did a new compression test.



As you can all see, the compression went up a bit in cylinders 1, 2 and 4. But I lost compression on cylinder 3, about 10 psi.

So with this, I'm going to call it, I have problems with the valves in cylinder 3, and need to pull the head and send it to the machine shop to fix it.

Now, will I do that? That is a different story, the idea of doing a k-swap is starting to feel pretty good. I'm going to think about it for the next couple of weeks.

Anyways, thank you everyone for the advice, you were all a great help!!