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burnt exhaust valve repair

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jn-mini View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Topic: burnt exhaust valve repair
    Posted: October/04/14 at 11:13pm
'06 Mini, just shy of 100k miles.

Back in '09 when it was still under warranty it first had a burnt/stuck exhaust valve.  Northwest Mini did the warranty work and we've been more-or-less ok since then.

A few weeks ago it starts misfiring, I take it into my local shop (not NW Mini) they check the compression and give me a $3.5k estimate to fix what appears to be another bad exhaust valve.  That's a bit steep for the age of the car so I figure I'll give it a go myself -- (it's been about 20 years since I've done this sort of work...)

I got the cylinder head cover off this afternoon and the first thing I see is:
bolt 11

...a missing cylinder head bolt.  It doesn't feel like the head sheared off or anything, they just forgot it 5 years ago.  I don't imagine this contributed to the new problems we're having now, but seriously?  How do you miss a bolt when you're putting the head back on?  

Any way, long-time lurker here -- with all the videos you guys have already posted I'm pretty confident I can get through this!  Thanks in advance!

-J&N
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SMOG Quote  Post ReplyReply Direct Link To This Post Posted: October/05/14 at 10:03am
Oh man!  Warped head from missing bolt????  Maybe Corners could chime in....


I wish there was a local MINI Dealership, like our Honda, Subaru, Mazada and VW.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote valvashon Quote  Post ReplyReply Direct Link To This Post Posted: October/05/14 at 8:14pm
Hello from a fellow West Seattleite!  I highly recommend Engine Machine Services at 309 South Cloverdale (right down the hill!)  Their number is (206) 766-9810.  They did an excellent job on my wife's MINI (MINIMNT, if you've seen it around) and were very reasonable.  Machining the head plus install of one exhaust valve and whatever seals and guides it needed was $461!  I think that's incredibly cheap and the car is running great- it's got more power than it ever had before.  Exhaust valves are $38 each so that's why we only changed out the burnt out one.  I would also highly recommend getting the cylinder head tool kit from an eBay seller.  The hold the upper sprocket tool was highly useful when it came time to remove and replace the head.

Here's what we found when Corners and I pulled the head:


Here's the link to what the special tool kit looks like:


$75 might seem like a lot but this kit or one like it (many sellers have them) makes the job go quicker and much easier.

I'd love to help since you are near but we are moving up to the Admiral District this week.  Most stuff is packed but I could probably dig out my Bentley manual or a torque wrench for you if you need one.  Corners still has the tool kit I bought otherwise I would volunteer that as well.

Good luck with it.

Bruce




Edited by valvashon - October/05/14 at 8:18pm
...Now mom may drive to the grocery store, But that's not what this car is really for...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: October/05/14 at 10:26pm
Perhaps I'm being optimistic, but we want our mini to go another 100k so a little money for the proper tools doesn't seem like a problem to me. 

Thanks for the tip on Engine Machine Services-- Google says they're closed permanently though??  I'll try giving them a call tomorrow.

I didn't get much further today, except I found that the screw plug (part #4 here) by the missing bolt is completely stripped on its torx side -- so maybe that tells the story?  They couldn't get the screw plug out to remove the timing belt guide, which means they wouldn't have access to that  cylinder head bolt so they just skipped it??  Dunno.  

Glad to be getting my hands dirty again at least!  

J&N - West Seattle
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Post Options Post Options   Thanks (0) Thanks(0)   Quote valvashon Quote  Post ReplyReply Direct Link To This Post Posted: October/06/14 at 10:51am
That's an odd way to put the engine back together, especially at a shop with direct access to every part needed.  I hope Kurt weighs in on this soon.  How about a good picture of the affected area- that would help me visualize it better.

Sure hope EMS isn't closed- their work was top notch!

Bruce


...Now mom may drive to the grocery store, But that's not what this car is really for...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: October/13/14 at 10:57am
It's been a slow week.  I got my mini-cam-sprocket-holding-tool Thursday but didn't get back into the garage until Sunday morning.  Nice that the tool came with the temporary engine mount -- I was a little concerned with how I was going to get the head off with the engine supported from above.  Problem solved!

There was the missing bolt by the timing chain, and also the 2nd small bolt by the timing chain wasn't torqued down at all -- maybe finger-tight at best.  The other 10 (big) bolts all seemed fine.  I got the plugs out to remove the timing belt guides -- but the stripped one I think I'll need to replace or the next time around I might not be able to get it out.

I don't see any obvious chips/cracks in any of the valves, but there's a lot of carbon/gunk build up that I haven't gotten cleaned off yet.  


  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CORNERS Quote  Post ReplyReply Direct Link To This Post Posted: October/14/14 at 4:33pm
I just noticed this post. (This forum does a terrible job of providing notifications, at least for me anyway - email me at kurt@hammondjp.com in case of any assistance needed)

Is everything sorted out? 
I was going to say that the previous mechanic maybe forgot to install the two smaller bolts but if you found one that was loose, chances are the other one is in the oil pan. I don't suppose it will hurt anything being down there but if you have the time/energy to do so, might be a good idea to pull the timing cover and check for any damage it might have caused on its trip to the bottom of the engine. 

What did your local shop say about your misfiring? Did they do a leakdown test in addition to a compression test? Those missing bolts should not have caused any head gasket related compression issues - they are there mostly to prevent any oil leak from the front of the head. 
A leakdown test would help show where is the problem. In most cases if a valve is sealing badly enough to cause a misfire, you would see it. How were the spark plugs - were any of them loose? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: October/15/14 at 10:54am
None of the spark plugs were loose -- but that was after the local place did the compression and leakdown test, so I can't say how they were before.  The leakdown test narrowed it down to the top of cylinder #2, "most likely a burnt exhaust valve" in their words.  Tonight I'll clean the head up and hopefully I'll be able to see something more definitive than a little build up.   

I saw no sign of any leaks around the missing bolts.  It seems to me that those bolts can't be removed when the timing chain guides are in place, so I don't see how the missing one could have worked its way out unless it sheared -- and it doesn't look like it did.

That's a good point though -- no reason not to check the oil pan for it just in case.  But if it's there and it caused damage along its way I'll be getting in over my head very quickly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CORNERS Quote  Post ReplyReply Direct Link To This Post Posted: October/15/14 at 11:03am
What were your compression numbers? How much lower was Cyl 2 than the others? It takes a pretty big leak to cause a misfire. 
Did they really do a leakdown test? If so, they would have been able to definitively state whether it's intake or exhaust. They would be able to hear the air leaking into the exhaust manifold, intake manifold, or crankcase. It sounds like they just did a dry and wet compression test and they are just guessing about anything else. 

When leakage is due to a valve it's almost always exhaust valve. I'm wondering if they just gave you a canned reply. It should be pretty easy to spot an exhaust valve that is burned badly enough to cause a misfire. It will have sort of a heart shape to it where the exhaust gases went past. 

If the smaller head bolt is captive when the chain guides are in place, I wouldn't worry about it. The technician probably got interrrupted and forgot to both tighten the first bold and put in the second bolt. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CORNERS Quote  Post ReplyReply Direct Link To This Post Posted: October/15/14 at 11:07am
Oh, and before cleaning anything - get some pictures of Cyl2 and another cylinder, both piston and combustion chamber. It might provide some diagnostic information.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: October/15/14 at 11:24am
from their write-up:
Quote ...test further, find misfire occuring on cylinder #2. Check spark, is good. Check compression, find a little low at 150 psi. Perform cylinder leak down test, find 70% leakage on cylinder #2. Add oil to cylinder, stays at 70% leakage; oil also vanishes down past rings very quickly. The fact that the CLT stays at 70% even with oil added indicates problem is most likely top end, most likely burned exhaust valves.  Cylinder head removal recommended as next step.

I swear I took some pictures right when the head came off-- but I'm not finding them now.  I'll take some more tonight.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: October/15/14 at 9:59pm
I spent a few minutes cleaning the cylinder head with a brass brush.  Sadly(?) nothing super obvious on #2:


so I put a little soapy water on the valves and blew the shop air from behind -- sure enough:


Bubbles!  The few bubbles on the right exhaust valve were blown over from the left side -- there were no bubbles coming from the right valve that I saw.

So now the question is, do I take the head in to an auto machinist?  Or do I pick up a valve spring compressor tool, some lapping compound and clean & lap them all?

Thanks for any input -- this is all new to me from this point forward...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote valvashon Quote  Post ReplyReply Direct Link To This Post Posted: October/15/14 at 11:08pm
If you've gotten this far into it I would again recommend Engine Machine Services if they haven't closed up shop.  Undoing bolts is easy compared to precision grinding.  Unless you have done it many times or are in some third world country where everybody grinds their own valves I would leave this for the professionals.  It will reduce greatly your chances of having to open the thing up again.

Bruce

                                                                                                                                                                              
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: October/16/14 at 11:12am
Too bad-- their number has been disconnected and my Google skills aren't turning up a new location or number.

I guess I'll start calling around to other places unless anyone has a recommendation?

Thanks as always
J&N - West Seattle
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: October/20/14 at 8:57am
I took the head to Pacific Auto Machine in Renton Friday.

3 or 4 valve springs are upside-down, and there's a fair bit of pitting on a few of the valves that he could see without even taking anything apart.  So, sounds like I'll be getting more than just 1 new valve, but I'll have to wait to hear more.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jn-mini Quote  Post ReplyReply Direct Link To This Post Posted: November/19/14 at 1:25pm
All fixed!  We moved down to NE Tacoma while this was happening, so that was great timing to be working on this!

Pacific Auto Machine ground all the valves, installed the new seals, and flattened the cylinder head.  No valves needed to be replaced.  Out the door for under $400 I think.  Nice!

Only issue I ran into putting things back together was that the new thermostat I got was bad -- it wouldn't open so I was overheating after a few minutes if just idling in neutral.  I replaced that again and everything seems good now.

Now I just need to figure out why I'm getting so much build-up on the valves that they've caused problems twice.  Someone suggested having the fuel injectors cleaned might help so that seems like an easy enough next step.

Thanks all!
-j&n


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