V7 Sport Head Leak Mystery

[Missionguzzi]

I've recently finished an engine rebuild on a V7 Sport.  Bike starts and runs fine, but has an untraceable, and so far unfixable, oil leak from the left side head.  This leak only appears after the bike gets hot.  I've redone the top end 4 times now, with new base, head and rocker gaskets and o-rings.  I even added high-temp seal to all the gaskets on one of the attempts.  The leak continues to appear after the engine heats up, enough to soak my boots after a 5-mile ride.  I did a light valve job, cleaning the head thoroughly, lapping the valves, etc., to no avail.  Based on close observation by myself and another, there is no leak at the head gasket or the valve cover gasket; they are completely dry.  There is visible oil at the front head bolt (in the spark plug well) and the rear head bolt, the cylindrical nut inside its own well.  The upper access nut for the rear well is oil-tight.  All the valve cover bolts are oil-tight.  The spark plug is oil-tight.  The drain channel from the head to the block is clear.  The oil feed banjo is oil-tight, and the oil passages to the rocker spindles are clear and flowing properly.  This is absolutely maddening.  I'm suspecting a small crack somewhere in the head, maybe the underside of the oil feed passage, but can't find anything even under good light and a magnifying glass. 

Has anyone else ever experienced such a thing?  What am I missing?  Heads are properly torqued to 32 psi.  I've rebuilt a couple dozen old Guzzis, Loop and Tonti, over the past 3+ decades, and many other cars, bikes and trucks.  I don't think it's due to inexperience or ignorance, although I'll admit the latter when it comes to this leak.

Any tips are welcome.  If you've ever seen a similar problem, please tell me what you found and how you fixed it.  Thanks in advance for your input.

[guzzisteve]

The short studs have an oring under the cylinder. My guess is it's bad if you have oil in spark plug area next to stud nut.

I have a V700 head that is porous casting but it only drips after hot. I have located it coming out of the aluminum. I have to get it coated inside the pressure drilling.

[Antietam Classic Cycle]

My '69 V700 did the same thing, nothing I tried fixed it. Finally gave up and replaced the head. No more leak.

[pehayes]

In all  your description  you never seemed to mention the top-center head stud and nut.  Maybe I missed that?
The top-center head stud and nut are 'outside' of the rocker chamber.  There is a large cover plug that has to be removed to gain access to that top-center stud and nut.  An older version of said cover plug was an external hex and used a large aluminum crush washer to seal.  Later models used a smaller recessed Allen hex.  This later version used an o-ring to seal the plug against the head.  These o-rings are notorious for getting hard, flat, and/or cracked due to many heat cycles.  That particular o-ring should be considered a 'one-time' use and discard.  You might get away with two or three removals, but after that it is sure to leak.

The four studs which secure the head and the rocker frame have an obvious  o-ring placement.  However, the shorter top/center and bottom/center studs are not so obvious and many people have installed o-rings incorrectly.  Have you ever removed the cylinder barrels themselves?  The cylinder base gasket goes directly against the engine casting.  The o-rings for top/center and bottom/center now go directly on top of the gasket.  Look underneath the cylinder barrel casting and  you will see a 45 degree chamfer or relief for those two stud holes which allows for gentle crushing of the o-ring and thence sealing against any oil migrating up the outer surface of the stud.  I've seen many with the o-ring under the gasket against the engine.  Crushes the o-ring too much and fails to seal.

Patrick Hayes
Fremont CA

[bigbikerrick]

I had a square head engine on a cal II that did the same thing. I tried everything,and finally replaced the head. It had a porosity I could not find . It also would only leak when hot.
Rick.

[Missionguzzi]

O-rings are all in place properly, and have been replaced twice now.  No difference in the leak.  The large nut (cover plug) which covers the access to the upper center stud is well-sealed with a new crush washer and exhibits no oil around the threads or directly beneath it.  However, there IS oil at the cylindrical upper head nut itself, and it appears to pass down the open channel toward the spark plug and lowest head nut.

I completely rebuilt the engine, from the sludge trap to the heads and everything in between.  Its condition before the rebuild is unknown except that the bike wasn't running right and was leaking from MANY points.  Now there are no other leaks except this one.  It very well could be porosity of the casting, because there are no visible cracks or other signs which may be causing the leak.  When the engine is just fully warmed up, the leak begins.  I shut it off quickly to see where the oil can be seen on the fins and where it CAN'T be seen (to rule out certain sources, like the head gasket and rocker cover gasket).  Base gasket and cylinder itself are completely dry, so I ruled out those fittings and the base o-rings. 

I'm not sure how to find if there is porosity or a hidden hairline crack in the head.  I've tried spraying penetrating oil into the head, but of course it drains down the oil-return hole and down the push-rod channels, so can't really isolate it.  I might try boiling it to see if air bubbles come out of any odd places - if I could even see it.

I'd love to find a new head (left-side head for a V-7 Sport), but they are rarer than hen's teeth.  I suppose I could use an Ambassador head, but I'd need to replace both sides, and it would be kind of a mongrel V-7 Sport....  but not out of the question, assuming I can find some.  Maybe the Eldorado heads would fit as well, not sure.

Thanks for your ideas and keep 'em coming!

[Antietam Classic Cycle]

AFAIK, the V7 Sport head is the same as an Eldo head. There are several fin configurations on Eldo heads.
https://www.thisoldtractor.com/moto_guzzi_loopframe_cylinder_head_comparison.html

[Moparnut72]

When I worked in a shop overhauling radial aircraft engines we used a product which I believed was used to seal aluminum cases. Unfortunately I didn't ask why we used it. The main reason was probably because the original manufacturer did. We didn't just overhaul the engines but restored them to the way they came out of the manufacturers factory. We used red Glyptal which was probably 1201b. I would like to provide a link but I haven't figured out how to do it on this new to me laptop. If you can't find it let me know and I will fire up the tablet and provide a link.
kk

[Tom H]

Even though I have never figured out why the upper and lower studs needs an O ring.

Even though you said all O rings are installed correctly...You DID, slide on the base gasket WITH the oil hole positioned correctly, then an O ring on the upper and lower studs, then installed the cylinder and head gasket WITH the oil hole correctly, ect, ect?????

And to be clear, it's just one side?

Tom

[pehayes]

I'm not sure how to find if there is porosity or a hidden hairline crack in the head.

Now this triggers a memory for me.  I bought a 98EV new.  After 6 months it developed a similar oil leak to yours.  I eventually tracked it down and got a new head under warranty.  Its been 100K miles so I forgot all about it.

You can find oil leaks by cleaning the area fastidiously and then spraying the clean/dry metal with the cheapest foot powder you can find.  Go for a ride and the leak will soon show up as a brown stain in the otherwise snow-white area.  Bingo!

When the head is constructed new at the factory, there are some oil passages that get drilled from the outside and thereafter are plugged with a malleable metal plug hammered into place.  I think it is zinc or potmetal or such.  One of my hammered plugs leaked but didn't show up for 6 months.  We tried using a tapered punch to re-hammer it, but in the end only a warranty head solved it.  Look carefully on the outside of your head.  How would  you drill oil passages that intersect inside the head's metal casting?  You have to drill one or the other from the outside and plug the leftover hole.  I'm betting on this for you.

How to solve it?  After another fastidious cleaning  you can cover the plug with some grey JB-Weld or such to seal it into place.

Please report back.

Look at this pic which I stole off the Internet.  The oil passages are all drilled AFTER the casting is made.  The YELLOW arrow is the oil feed into the head.  The RED arrows are drilled at 90 degrees to pick up the oil and feed it to the rockers.  After drilling, the red arrows are plugged with a hammered soft metal plug.





A more modern head may have those red arrow passages drilled at a 45 degree angle rather than this older 90 degree version.  You get the idea.

Patrick Hayes
Fremont CA

[pehayes]

Even though I have never figured out why the upper and lower studs needs an O ring.

Because under crankcase air pressure, oil can migrate up past the stud's threads and all the way up to the nut at the top and bleed out to atmosphere from there.  The o-ring atop the base gasket seals the stud and keeps oil inside the engine.

Does that work?

Patrick Hayes
Fremont CA

[Tom H]

Highly plausible. But darn it, now I need to be sure the upper and lower stud threads are drilled through the block or a blind hole.

With all due respect, this is one of those things that make me wonder!!

Even if it is a through hole, I really still find it hard to believe that the oil can go past the tightened against each other threads (but..there are thread sealant products from Loctitie to keep this from happening in other applications where the bolt is "in" fluid), then up the stud, and at least in the case of the lower stud with a washer that "could" be sealing the hole. AFAIK, the upper does not use a washer, at least I do not remember ever finding one. Also there should be very little air pressure in the block due to the breather.

And another one...Why put sealant on the two lower bolts for the rear carrier bearing. Neither sit "in" the oil. All would get splashed, why only those two need sealant???????

Sorry for the thread drift.

Tom

[Missionguzzi]

To reiterate, all the o-rings are in place correctly.  Base gasket first with the drain hole where it should be, two o-rings on top of that at the top and bottom stud, cylinder on top of that, head gasket, head.  4 o-rings on the studs beneath the rocker mounting block.  Head torqued to 32 ft/lbs, "x" pattern in 5 ft/lb increments.  Meticulously cleaned with brake cleaner spray, then started engine to warm it up, then located the wet areas using a bright light and surgical mirror around the entire circumference of the head.  Also checked the high-pressure oil passage where they are drilled, and found these completely dry.  NO leak at head gasket or rocker cover gasket, nor at the base gasket, of course.  All studs are dry at the bottom, that is, no oil is migrating upward from the crankcase.  This leak seems to originate somewhere in the head, about 2 fins above the head gasket and below the rocker cover gasket.  It collects a little on the upper stud nut, and on the lower stud nut, maybe following gravity from top to bottom.  From there the oil drips off the 2nd fin above the head gasket seam.  I'm nearly convinced there is porosity which allows oil from the pressurized passage to seep through to the lower side of the head, and then it drips from there.
I'm going to rig a pressure test for the head (off the bike now) by attaching a hose to the oil feed banjo and blocking the rocker spindle lubrication holes with a piece of rubber and bolting the rocker cover through the head.  This will prevent the 120 psi pressurized air from just blowing out the spindle lube holes, and will force it out any other place (pores, cracks?) it can.  Submerge this in soapy water and watch for bubbles.  Maybe this will work.  I'd like to use boiling hot water, but it might make it difficult for me to work with the submerged head.

Also, this is just the left side.  Right side is perfect.

I'm looking for Eldo heads now.  I believe the V7 Sport head has bigger valves, but I'll confirm.  If I change to Eldo heads, I'll change both sides (unless the valves are identical, in which case I'll just change the left side).

[huub]

if you fitted all the O rings , its probably a porous casting.
i had the same with my le mans 2 , when rebuilding it i had the heads bead blasted , and once rebuilt it had a irritating oil stain at the left sparkplug.
a friend worked at a iron foundry at the time , he had the head impregnated at work.
no idea what they used

[Missionguzzi]

It would be nice to find something that would impregnate all the imperfections in the head.  Have no clue what it might be, though.
Good news is that I confirmed, as someone else suggested, that the V7 Sport head is identical to the Eldorado head, left side is 13 02 22 60.  This will make it much easier to find a replacement head.  I thought, incorrectly, that the V7 Sport had bigger valves.  I guess the difference is in the camshift lift, which requires the cutaway section in the piston crown.

[Antietam Classic Cycle]

And another one...Why put sealant on the two lower bolts for the rear carrier bearing. Neither sit "in" the oil. All would get splashed, why only those two need sealant???????

Those two bolt holes go through into the inside of the engine, unlike the other six which are "blind" holes. On early engines, without a sump spacer or deep sump, they were actually under the oil level, so would leak unless sealed. Even on later engines, I believe it's important for them to be sealed.

[Vagrant]

Re, the #5 reply from Missionguzzi in his first paragraph. I had a 72 Eldo that the tower under that cap nut had a hairline crack in it that was only visible if you put extra torque on the cap nut. But, it opened up and leaked when hot.  JB eld might have fixed that one. I'm sure the tap caught or bound up when tapped at the factory.

[pehayes]

and at least in the case of the lower stud with a washer that "could" be sealing the hole. AFAIK, the upper does not use a washer, at least I do not remember ever finding one.

Not a thread drift.  We're still investigating a leak.

The upper/center and lower/center studs DO require a washer under the nut.  You would never want the steel nut tightening directly against the aluminum casting of the head.  The required washer is steel.  In the case of the lower/center stud, that washer is the same as the other four used on the longer/outer studs.  I once confronted and Eldorado where the owner had used an aluminum crush washer under the nut to help stud sealing.  Bad juju.  When fully torqued, the aluminum crush washer distorted and 'crushed' as intended with the center hole becoming smaller and smaller as the washer gripped the stud.  It was then a serious task to get that head off of the bike!!!

The top/center stud uses a special Allen barrel nut rather than a traditional hex nut.  Under that Allen barrel nut is a unique washer.  What is unique about it?  I don't know.  I just spent time looking at Parts PDFs for V7-Sport, Eldorado, and T3.  Each engine requires a total of TEN washers for the regular nuts on both sides of the engine.  Then they require TWO different washers which belong under the Allen barrel nut.  Different part numbers in each case, so there must be something unique about that washer.  OD?  Thickness?  Material?  (The following quantities refer to BOTH sides of the engine.)

The V7-Special calls for 10 of #95-10-03-15 and then 2 of #95-00-42-10.
The Eldorado calls for 10 of #14-01-84-00 and then 2 of #95-12-91-80.
The T3 calls for 10 of #14-01-84-00 and then 2 of #95-12-91-80.

I often find the washers for top/center and bottom/center studs stuck directly to the heads and they need to be pried out.  Reach with a magnet which won't adhere to the aluminum casting but might adhere to a steel washer stuck in place.

Frankly I was never aware that the top/center barrel nut required a different washer.  Clearly it does by booklet inspection.  I'd sure like to know exactly what is different about this unique washer.  Hope this data helps.

Patrick Hayes
Fremont CA

[Antietam Classic Cycle]

The top/center stud uses a special Allen barrel nut rather than a traditional hex nut.  Under that Allen barrel nut is a unique washer.  What is unique about it?  I don't know.  I just spent time looking at Parts PDFs for V7-Sport, Eldorado, and T3.  Each engine requires a total of TEN washers for the regular nuts on both sides of the engine.  Then they require TWO different washers which belong under the Allen barrel nut.  Different part numbers in each case, so there must be something unique about that washer.  OD?  Thickness?  Material?  (The following quantities refer to BOTH sides of the engine.)

The V7-Special calls for 10 of #95-10-03-15 and then 2 of #95-00-42-10.
The Eldorado calls for 10 of #14-01-84-00 and then 2 of #95-12-91-80.
The T3 calls for 10 of #14-01-84-00 and then 2 of #95-12-91-80.

I often find the washers for top/center and bottom/center studs stuck directly to the heads and they need to be pried out.  Reach with a magnet which won't adhere to the aluminum casting but might adhere to a steel washer stuck in place.

Frankly I was never aware that the top/center barrel nut required a different washer.  Clearly it does by booklet inspection.  I'd sure like to know exactly what is different about this unique washer.  Hope this data helps.

Patrick Hayes
Fremont CA

Guzzi changed from flat washers to wave washers - 10 large o.d. ones and 2 smaller o.d. to fit down in the "12 o'clock" position.

[Tom H]

Can't remember ever finding one in the upper stud hole. Guess they must have been stuck to the head.

I'm pretty sure that 40 years ago I was likely the first one to pull the heads on my Ambo and Eldo. I just really don't remember a washer on that stud. I think I would remember cursing that washer since I don't see how to just slide it over the stud with my fingers. Guess they must have been stuck to the head?

Thanks for the info!
Tom

[John A]

Often the washer at the twelve o’clock position stays stuck on the aluminum, which is ok as long as it’s there. Feeling around with a small magnet on a stick will help determine if it’s there. Its od is smaller to fit in the hole, I assume so they didn’t have to hog out the space for it and an allen nut was used for the same reason

[bigbikerrick]

It seemed to me that the two  "different" washers  had a slightly smaller outer diameter than the rest. 
Rick.

[5154guzzi]

Like Vagrant`s  Head, I also found a hairline crack in the threaded boss of the upper middle stud

[Missionguzzi]

First, regarding the washers on the head stud nuts:  All 6 require a washer.  As stated, the 5 which are accessible for the normal 17mm nut are one size; earlier ones were flat washers, later were wave washers.  Don't think that makes much difference.  The "12 o'clock" stud with the barrel nut uses a washer with a slightly smaller outside diameter so it will fit down through the recess onto the stud.  The other 5 washers have a larger O.D. which will not fit through the threaded recess where the cap goes.

Next, I can find no evidence that the cap nut has a crack or is leaking in any way.  It is a solid fit, and dry even when the leak is visible.

Third, I made a Rube Goldberg test apparatus to pressurize and check the oil feed which goes to the rocker spindles.  I fit a rubber hose to a banjo fitting, secured with a hose clamp, and bolted the banjo fitting to the oil feed port.  On the other end of the hose I fit a quick-disconnect fitting for my air compressor, which had a barbed insert for the hose (lucky I had that in my tool chest) and secured with a hose clamp.  Then I found some thick rubber seals and bolted them between the rocker yoke and the head to seal that tightly shut, and tightened them down firmly.  This allowed me to apply 120 psi to the oil feed passages.  I then submerged the entire head into a large bucket with hot water, and watched for bubbles.  I saw a few small, random bubbles, but no "stream" of bubbles coming from any particular place.  I moved the head through 360 degrees to watch closely at all locations and between the fins.  Nothing.  The few random bubbles were most likely just trapped by surface tension onto the head, and broke loose with the little bit of motion in the water.  I expected to see a stream or flush of bubbles which would indicate a leak, but unfortunately, did not.  However, I think that compressed, hot oil at roughly 35-40 psi might leak (on a hot engine) more than air, even at 120 psi.  Air will compress, while liquid will not (thus the rationale for hydraulic systems over pneumatic systems).

Frustrated that I'm not finding a cause or specific location of the leak.  I can purchase and install some Eldorado heads, but am concerned that there may be some other cause not inherent to this particular head, although I can't conceive of anything I haven't already checked.  The only time I can detect the leak is when the engine and oil are hot and has run for a few minutes.  Logically, those conditions are changing either the dynamics or the physical structure of the head, but short of cracks or pores which only manifest themselves when hot, I don't know what else it could be.  I thought of a warped head, which could be exacerbated by temperature, but the leak is not occurring at the head gasket (or rocker cover gasket), which are the only places that a warp would change the seal between mating surfaces.

I may purchase the Eldo heads and install just for grins, but if it doesn't solve the problem, I'll be out even more $$$ and feel like a real dumb-ass.  Then again, if it DOES solve the problem, I'll thank all of you, pat myself on the back and feel like a hero.  Decisions, decisions......

[Pescatore]

Maybe the water is not hot enough to expand the leak source.
You could put the head in an oven to get it really hot.
The other factor, when mounted on the bike, is vibrations.

I would also want to find the source.  Talc, or foot powder as suggested, would be my next experiment.

[wirespokes]

I'm thinking the head isn't hot enough, so how about this: Heat it in an oven to 300F and then connect the air. Listen for the leak. Fill the cavity with ATF and watch for the red stain.

[Missionguzzi]

Good suggestions.  I might have trouble heating the head to 300F (I could heat it in the oven, but then I'd have trouble handling it to my workshop, connecting the air, putting it in water and then moving it around to observe for leaks).  I can try it.  I like the ATF suggestion, which would show up wherever it leaks, a lot better than my nice, clean, clear oil.  If I had a hydraulic cylinder, I could put a good bit of pressurized oil/ATF into the head and force a leak, but....  I can't figure out how to transfer pressure from my hydraulic jack to the head.  It would require a bunch of special fittings and a hose or pipe capable of handling the pressure.
I've dealt with porosity a bit during my manufacturing career, and it's a product of inconsistent process control.  Casting requires pretty exacting parameters - temperature, pressure, time, material, tooling - and sloppy processes can result in porosity, among other problems.  Sometimes it's obvious, sometimes it's hidden, sometimes it's in an area which will never cause a functional problem.  But it is a structural defect which can worsen with time, temperature fluctuations, pressures, torque stresses, etc.
I found a set of Eldorado heads, which are in transit.  They'll need to be cleaned up and a valve job, but they should be suitable to replace the V7 Sport heads.  I'll post after they're installed on the bike and let you know if that solved the issue.  If not, then I think I'll check myself into the Alzheimer's facility, and pass my time watching TV re-runs.  Less stressful.....

[wirespokes]

LOL

After heating in the oven, don't submerge in water - that would only cool it down. Since it only leaks when hot - out in the air - do the same. Heat it up and see if it leaks.

I was thinking you could fill the cavity with ATF, then apply 100 psi air to it. That could provide enough pressure to force fluid through the crack.

Another possibility is using a hydraulic pump like a port-a-power - a hydraulic ram body-working tool. That shouldn't be difficult to hook up.

[Vagrant]

You need to put it in a big enough metal container to submerge it then heat it in the water to almost boiling. That should show up the issue.

[Missionguzzi]

OK, for all of you who are sitting on the edge of your seats waiting for an update.....   I found some old Eldorado heads on eBay.  Bought them, cleaned them and did a valve job.  The heads were NOT identical to the V7 Sport heads, with a few minor differences in the fin configuration, part number stamping, etc., but functionally the same with the same size valves.  (It seems that the V7 Sport had at least 3 different configurations of heads during its short production span).  I installed the Eldo heads as per normal procedure except I used Copper Coat spray on the head gaskets.  Torqued everything down and let it sit for a couple of days, as I had some trepidation about starting it too soon - and generally just nervous about the possibility of finding that the leak was not solved.
Well, thank the Lord, the leak is gone.  Rode it around long enough to get the engine fully hot, and drip-free!  I am deducing that the leak was due to a micro-crack or porosity, nearly impossible to detect the exact location, but big enough to allow a pretty heavy drip after the engine warmed up (and not UNTIL it warmed up).
Thanks to all for your suggestions, as a head defect never would have occurred to me.  Too many other human or material factors (gaskets) to even think the basic head might be bad.  But it finally worked out, and I now have a running V7 Sport to turn over to its rightful owner.