Codes 25 and 26

[suprabee]

Any gurgling noises on a cold start?

Usually a stuck valve would make a big ticking noise, wouldn't be hard to miss.

well Yes, there has been air in the heater core off and on, but due to leaking hoses, and for a while I had an unknown leak from the rear water fitting union bolt at the back of the head....not enough to drip onto the ground but enough to let in air. All of these problems have been fixed when I did the turbo last Feb/March. My 90 degree hose by the thermostat housing I found was leaking just last week because I used a cheap clamp instead of the Toyota ones. (won't do that again). As stated above, Never had any mixing of fluids, no overheating, and performed test for combustion gases in coolant multiple times over the past year, both before and after the codes started.

Drive train is very quiet, no valve tapping

..waiting on friend with air compressor to come over for leak test...

 

[3p141592654]

Let us know how it goes.

 

[suprabee]

Update....

finally got my hands on a compressor today and tested the #4 cylinder with low compression and also the #1 (which measured normal) for comparison using 120 psi on the compressor.

#4 has an exhaust valve leak. There was air coming out the tailpipe, enough that I could easily feeling it with my hand, and I could also hear the leak at the tail pipe. Compared to the #1 cylinder which had absolutely no air, nor any sound coming out the tailpipe, so I know that my #4 exhaust valves are the issue.

Then I checked if air was coming out the intake at the throttle body, no air..good

Then checked for air bubbles at the rad..none..good

Then I checked if air was coming through the crankcase through the top valve cover outlets (what I'll call the PCV outlets) and..yes..there was. I had the valve covers hard piping removed to gain access to the #4 spark plug. It was less than was coming out the tailpipe, but I didn't expect it to be as much as it was. So, next I pulled the oil dipstick, and covered the two valve cover outlets with my fingers. Once I did this, I could hear oil gurgling in the crankcase and air coming out the dipstick tube.

This worried me, but I then did the same check on #1 (which has normal compression) and the same results occurred with oil gurgling in the crankcase and air coming out the dipstick.

I've previously opened the dipstick and oil filler cap with engine running many times to see if there was air coming out caused by blow-by and there was none, so I think this is not a problem since I have no other bad ring symptoms (other than low compression), and the #1 cylinder responded the same when pressurized. I'm aware that some blowby is normal.
From my description does this sound like normal blowby?
...also the engine was dead cold
Rick

 

[suprabee]

measured the exhaust valve clearance today, engine was cold (in inches):

spec on exhaust side is 0.008-0.012
#1 - 0.009 & 0.009
#2 - 0.009 & 0.009
#3 - 0.009 & 0.007
#4 - 0.008 & 0.007 <==cylinder with low compression
#5 - 0.007 & 0.008
#6 - 0.008 & 0.008

I could spin the valve buckets around with my finger, so they are not sticking, cam lobes all look great. I tapped on the valves a little bit allowing the springs to recoil them against the head in the hope to maybe loosen up carbon build up on the vale face and seat. Also took an angled hose and through the spark plug hole spray some brake cleaner up onto the valves..again just hoping to loosen up anything that might be causing the leak before I pull the head.

So about the valve clearance measurements... would 0.001 of an inch too tight be cause of the leak? I don't think it would.

rick

 

[suprabee]

update...

I believe that I have resolved the low compression on #4. On my last post on Sept. 13th, I checked the valve clearances and also sprayed some carb cleaner into the cylinder. I took this last step a bit further by filling up the cylinder until cleaner was coming out the spark plug hole with the piston at the top of its compression stroke. Then pressed down as hard as I could on the valve buckets using a ratchet extension to extend the valves as far down as possible into the cylinder and into the carb cleaner to make sure they get soaked. Let this sit for 10-15 minutes, then turned the crank by hand for several complete rotations. Next, I positioned the cam lobes on #4 away from the valve bucket tops and used my large screwdriver to press down on the valve at the edge of the bucket, then quickly moved the screwdriver off the edge allowing the spring to recoil and slap the valve surface against its seat on the head. Did this maybe 10-15 times. Then turned the crank by hand several complete rotations which evacuated most of the remaining cleaner still in the cylinder. Put valve cover back on and cranked engine with starter for 30 seconds to obtain oil pressure (had EFI fuse and coil resistor unplugged). Then re-assembled everything and have been driving the car daily since then..about 10 days.

Idle is perfect, very calm and smooth and turning on the accessories will not effect it poorly like before, and no codes 25 and 26. Prior to all this cylinder cleaning, I was getting the codes every day or two after resetting the ECU since mid- June when the problem first started.

Also, there is an audible change to the engine. I noticed that when under small load, before any boost, I could hear the exhaust leak. It was especially noticeable with pass window rolled down and if I drove by..say...a large fence or wall jut off the side of the road, so the noise from the engine would reflect back at me. My best comparison is that is sounded like a steam locomotive...you know...chug,...chug...chug...chug. It was very very subtle, but I was aware of it. I know what I was hearing was the leaking valve/s on the compression stroke, and no it was not the exhaust manifold, its new and only has 3k miles since I replaced it and all the bolts are tight and torqued correctly to 30 ftlbs.


So, in addition to the perfect idle, no codes, that locomotive sound is completely gone now and under load the engine sound is uniform and relatively quiet.

I think there was carbon build up on the valve seat or valve surface, or somehow a piece of carbon from the piston head came dislodge and became stuck on the valve which was the cause of my leak. I was able to remove or dislodge all or some of it to the point that the valve/s are now seating properly on that one cylinder

I am sure that the problem is related to how I drove the car the day before the problem started. I was on a late night drive for several hours and decided to open it up and drove for about 10 minutes between 90-100mph on the open freeway. I had never driven the car that fast before, and I think doing that dislodged something. I know there was carbon build up in the cylinders because prior to October of 2009 (when I replaced the vale stem seals), they had been leaking for several years before I decided to replace them. The next morning while continuing my journey is when the codes and poor idle started (mid-June) Maybe just a coincidence, but I think this theory is plausible.



Yes, the final test would now be to check compression on that cylinder, but for now, its running better than it has in months, and as long as the codes are not thrown, idle is good, and that sound is gone, I'm happy and confident that my "home-made" sea-foam method has helped.

I'll update if things change and the symptoms return, or if I finally do a compression on the cylinder..but for now, I'm just sick of working on the car and happy to be driving it again, code free!

**update on Jan 18, 2011**
4 months later all is good, ie.. no codes and idle is stable.