Topic: Headgasket Leak/Engine Advice

[TwoTired]

I'm still skeptical those rings are bad.  Shows us a picture of the backside of the valves before cleaning.

[themagicalatsi]

The back side looks ok... no obvious sign of a blown gasket.  There is oil on the gasket surface between cylinders 1&2 and cylinders 3&4.  It was really stuck around the timing chain but cam up easily around cylinders 1 & 4.  I also noticed that studs between those cylinders (the shinny ones in the picture) are rather greasy at the base...  These can also be seen in the foreground (at the sides) of the 2nd and 4th pictures of the pistons that I just posted. 

The fact that there are only two cylinders with problems makes me think that there are no problems with the rings... It seems to me that the rings would wear evenly (more or less) unless there was a severe and obvious problem with the pistons or cylinders (which there isn't). 

I would post a picture of the head gasket and the valves but the camera just died...

I'm still skeptical those rings are bad.  Shows us a picture of the backside of the valves before cleaning.

Because the camera died, I will just have to describe what I saw... The valve seats of the exhaust valves cyl. 2 & 4 were as cruddy as their combustion chambers.  The valves weren't seating well at all.  The valve itself was rather rounded where it seats and just as nasty.  The machinist took a look at where the guide pokes into the intake runner and it was really clean, so he felt that it was unlikely that the oil was getting in there...

[TwoTired]

Because the camera died, I will just have to describe what I saw... The valve seats of the exhaust valves cyl. 2 & 4 were as cruddy as their combustion chambers.  The valves weren't seating well at all. 

Did you pull off the valve springs and check the valves wobbling in the guides while seated?

The valve itself was rather rounded where it seats and just as nasty. 

That's more evidence of valves not simply closing, but moving laterally. (which the guides are supposed to prevent.

The machinist took a look at where the guide pokes into the intake runner and it was really clean, so he felt that it was unlikely that the oil was getting in there...

I asked for a valve backside picture, because oil leaking past the guides gets burned onto the backs of the valve heads.  The valves remain way hotter than the runners do.

The runner to valve stem interface has high velocity gases passing by to help keep it cleaner.

[ofreen]

It was really stuck around the timing chain but cam up easily around cylinders 1 & 4.  I also noticed that studs between those cylinders (the shinny ones in the picture) are rather greasy at the base...  These can also be seen in the foreground (at the sides) of the 2nd and 4th pictures of the pistons that I just posted. 

Thius is why I'm thinking oil was getting by the head gasket into the cylinders.  I've seen it before on bike and car engines.  One of the reasons I've come to the conclusion over the years that a head retorque is a good idea.  Less than handy on bikes that require engines removal, but no less valuable.

The issues with the valve train wear is something else.  TT called it right, I'd say.

[ofreen]

3) while turning the engine over slowly with the kickstart I hear a "swish" (of air??) once per two revolutions

Another symptom that points to the head gasket not sealing.

[Deltarider]

Wrong ear!

[themagicalatsi]

I am thinking that the headgasket was most of the problem, the valves may be a small part of the problem, and the rings are probably fine.  I think this because the rings and valves in all of the cylinders should wear evenly (more or less)... It wouldn't make since that cylinder 2 & 4 are such a problem in comparison to the cylinders right next to them.  And if it was a valve or ring problem it would be obvious when comparing the valves or rings of the good cylinders to the bad cylinders.  The head gasket would be more of a random problem affecting random cylinders.  It also would cause some problems with the valves seating... What do you think?

The machinist did pull all the valves and check the wobble of the valve laterally.  It wasn't bad but it wasn't great either, this is why he suggested to do the guides. 

[HedNut]

Reading this post this afternoon...I felt like I learnt a lot today....good info....good stuff.  Keep it up!

[Deltarider]

Wrong ear.

If you are referring to the avatar, I believe the left ear is correct.

You are depicting our countryman as an imbecile who cannot even cut his right ear. It's a disgrace and I must object.

[sangyo soichiro]

Wrong ear.


If you are referring to the avatar, I believe the left ear is correct.

You are depicting our countryman as an imbecile who cannot even cut his right ear. It's a disgrace an I must object.

I don't know if there's an inside joke going on here, but...

On 23 December 1888, frustrated and ill, Van Gogh confronted Gauguin with a razor blade. In panic, Van Gogh left their hotel and fled to a local brothel. While there, he cut off the lower part of his left ear lobe.

Regardless, seem odd to have this discussion here....   

[TwoTired]

The head gasket would be more of a random problem affecting random cylinders.  It also would cause some problems with the valves seating... What do you think?

A head gasket that causes valve issues is a bit of a stretch, I think.  I welcome theories on how that can happen.

Leaking head gaskets always show signs of high pressure/ hot gasses passing over the metal ring (assuming a running engine). I don't think the pic you posted earlier shows that detail.

The machinist did pull all the valves and check the wobble of the valve laterally.  It wasn't bad but it wasn't great either, this is why he suggested to do the guides. 

The wobble is why you need both the seats and the valve seating face reground/ refitted.
I don't remember if the valve faces are surface hardened.  If so, they need replacement, or re-hardening.  The machinist should be able to figure that out, if he is worth the money your are paying for the job.

The pits worn in the valve stem tips require them to be ground flat.  The seated length/height at the valve adjuster must be checked. And if too short, then lash caps must be installed to restore that height/length (in order to restore the adjuster to valve stem geometry).  I'd go with all new adjusters, as well if you care about durability.   I think those have surface hardened tips, too, but I am not certain.

[themagicalatsi]

I only mean that the leaking of the oil into the cylinders could cause the valve not to seat properly due to buildup of crap in the combustion chamber... Plus this could mess up valve clearances and lead to some valvetrain wear... I plan on replacing all of the valves so they won't be a problem. 

Maybe, the valve guides are the main source of the oil getting into the motor... It could be... Either way, it sounds like there is a pretty good consensus that my piston rings are fine... The head gasket is obviously going to be replaced (so that won't be a problem, if it ever was) and I will have new valves, guides and seals (so that shouldn't be a problem either).

It looks like I will also buy a set of adjuster screws as well, like you suggest. 

Does this all sound good and correct?

[ofreen]

Leaking head gaskets always show signs of high pressure/ hot gasses passing over the metal ring (assuming a running engine). I don't think the pic you posted earlier shows that detail.

That was why I was wondering what the other side looked like.  But I don't know about the 'always' part.  In the past two years I have done the head gaskets on a couple 4 cylinder car engines.  One was an '87 Civic, the other a '94 Plymouth Colt, same car as a Mitsubishi Mirage.  Both were overheating because of bad head gaskets.  Neither showed any obvious damage to the metal inserts.

[TwoTired]

I think the replacement list is sound.

Are you getting the valve seats reground?

[TwoTired]

But I don't know about the 'always' part.  In the past two years I have done the head gaskets on a couple 4 cylinder car engines.  One was an '87 Civic, the other a '94 Plymouth Colt, same car as a Mitsubishi Mirage.  Both were overheating because of bad head gaskets.  Neither showed any obvious damage to the metal inserts.

Then there was no compression loss?

During combustion, the gasses get in the 1500F range.  Passing this hot gas flow over thin metal usually leaves a visible mark or distortion.

Overheating can be many things, though, clogged water jackets (passages through the head gasket).  Even compression loss into the water jacket which is faux overheating because the compression is too high in the cooling system and blows out the coolant, then the lack of coolant make the engine truly overheat.  (I fixed a Renault that failed in such a way.  The original cause was hose to the overflow reservoir got disconnected, low coolant distorted a cylinder sleeve and made the gasket seal fail.  I hated that car.)

Anyway, every bona-fide blown head gasket I've seen showed a leakage path across the metal of the gasket.

[ofreen]

Then there was no compression loss?

Probably was.  I didn't check.

During combustion, the gasses get in the 1500F range.  Passing this hot gas flow over thin metal usually leaves a visible mark or distortion.

You think it would.  But does it in every case?  In my experience it doesn't.

Overheating can be many things, though, clogged water jackets (passages through the head gasket).  Even compression loss into the water jacket which is faux overheating because the compression is too high in the cooling system and blows out the coolant, then the lack of coolant make the engine truly overheat.  (I fixed a Renault that failed in such a way. 

A typical symptom of combustion gases leaking into the water jackets is intermittent overheating.  The engine will run at normal temperature, then suddenly the temperature will spike.  Frequently, this will happen at idle.  That's what happened on the two cars mentioned.  There was no rapid coolant loss, just a steady one.  Changing out thermostats, water pumps, etc, doesn't cure the problem.  A new headgasket does.  Sometimes the appearance of the head gasket makes the reason obvious, sometimes it doesn't.  Sometimes there is the appearance of coolant in the oil (or vice versa) or exhaust, or deposits on spark plugs, sometimes there is not.  It seems like I've had the opportunity to look at a lot of head gaskets over the last few years.  It seems like head gaskets in Japanese cars are good for about 150,000-200,000 miles, then they begin to fail.  I've seen this in inline 4's and V6's.  And all the gaskets are not created equal.  The one in the Colt engine was actually crumbling.  The one from the Civic appeared as though it was made from the cover of an old Sears catalog.  The one from our Mazda 626 looked a lot like the head gasket from the OP's bike, soaked in oil.

Anyway, every bona-fide blown head gasket I've seen showed a leakage path across the metal of the gasket.

I don't doubt that for a moment.  I've read enough of your stuff over the years to know you are an excellent observer.  I learn something new every time I look into an engine.  I always try to learn as much about the history of the engine as I can to correlate with what I see.  I'll never see it all, and it is always interesting.

[TwoTired]

During combustion, the gasses get in the 1500F range.  Passing this hot gas flow over thin metal usually leaves a visible mark or distortion.

You think it would.  But does it in every case?  In my experience it doesn't.

I'm not making any guarantees.   
It's a strange world, sometimes.

A typical symptom of combustion gases leaking into the water jackets is intermittent overheating.  The engine will run at normal temperature, then suddenly the temperature will spike. 

Isn't that because the coolant level gets below the level of the thermostat and it fails to measure the coolant temp and open up until steam does the deed?
Could also be that at idle the water pump starves/ loses prime once air is introduced into the system.

So many different systems with their own unique characteristics and element placement....   

Cheers,

[ofreen]

Isn't that because the coolant level gets below the level of the thermostat and it fails to measure the coolant temp and open up until steam does the deed?
Could also be that at idle the water pump starves/ loses prime once air is introduced into the system.
So many different systems with their own unique characteristics and element placement....   
Cheers,

The gradual coolant loss was noted at the recovery bottle.  The system itself stays charged unless the recovery bottle is allowed to become empty.  Your point about different systems having different characteristics is right on.  Part of what makes it fun.

[TwoTired]

The gradual coolant loss was noted at the recovery bottle.  The system itself stays charged unless the recovery bottle is allowed to become empty. 

89 camaro 13,000 miles on engine
Coolant still in recovery bottle, albeit slightly low.  Radiator and engine low on coolant, thermostat high and dry.  Blown head gasket into water jacket.  Coolant escaping out #8 cylinder/exhaust (deposits on spark plug).  Pressure in cooling system higher than normal, bubbles in the recovery bottle when running.  Normal cool down cycle can't suck enough in from recovery bottle to keep coolant inside topped up.

Head gasket showed exactly where the compression was escaping.  No coolant in the oil or vise versa. (I changed the coolant anyway.)

Head warped (thanks GM service department for replacing a bad computer module (its 3rd) with another that won't turn on cooling fans and then watching in fascination as the temp goes sky high and it boils over, then they change the thermostat and watch it boil over again, then the manager notices no fans running and has them change the computer again, Problem solved!  Here's your internally damaged car back, sir.... freaking bozos)

Anyway, resurfaced head, new gaskets, and it's fixed.  Still have to change out the hardened overheated valve guide seals. (oil smoke on start up, but oil level consistent)  It's one saga after another with that thing.  GM won't get any more donations from me...ever.

OT...yes.  But, it is about head gaskets!

Cheers,

[ofreen]

Anyway, resurfaced head, new gaskets, and it's fixed. 

It's still a Chev, though.

[themagicalatsi]

I think the replacement list is sound.

Are you getting the valve seats reground?

Yeah, the valve seats will be reground and resurfacing of the both the head and the cylinder case.  I'm guessing he wound resurface the cylinder case if it turns out to be within specs. 

Thanks everyone for the help, it sounds like I am on the right track.

[themagicalatsi]

So... I brought the new valves into the shop today along with the cylinder case.   After the machinist took a look at the cylinder walls without the piston inside the cylinder he identified some scoring.  He is going to try to hit it with a bead hone and see if it helps at all...  My problem is that this makes me want to solve this problem but pistons are hard to find unless I want dynoman's 836 kit (and I can't afford that).  I have found a guy to regroove my pistons for K rings... but this won't help unless the hone removes the scoring.  

Really here is my question:  If the honing removes the scoring, do I really need new rings if mine are within specs?  If the honing fails, then what?  I'm guessing its time to save some money and go big... like 836?

[TwoTired]

The cylinder walls have wear limits.  Any "scoring" removal will increase the cylinder diameter toward the wear limit. So, how deep is the scoring?  Further, won't the honing to remove scoring make the cylinder dimension irregular or non-uniform?

I expect your used ring end gaps will now be excessive after honing.  And, your existing rings will have a score to match that of the cylinder.

If you really need to hone out a score, you are likely looking at new rings as well.

I didn't see any scoring in the pictures you posted earlier.

If you do approve the honing, the cylinders will have to checked/measured to verify roundness and choke (taper) if present, and then rings and perhaps pistons selected/fit for the bore's dimension.

[themagicalatsi]

I just got the head and cylinder case back from the machinist this afternoon... or rather my father picked it up because I am away at school.  Apparently, the cylinder walls are fine.  He did a light honing (I think) that removed the ____(a word I can't remember right now)... Anyway, he determined that the cylinder walls appear to be fine, so my rings are probably fine as well.  I will be returning home in a couple weeks to throw it all back together and see how it goes.  You should hear from me again at that time.