Rebuild time? Excessive blow-by?

[evanmc]

1985 110 2.5NA with 200K miles

Please take a look at the attached video -- I have excessive amounts of smoke/oil mist coming out of the filler cap. It's ex MOD, and the plate on the engine indicates it was rebuilt in 1995

So much so that oil mist is now landing on the exhaust, causing quite a bit of smoke.

So if I do need to rebuild (and the quote for this was an eye popping $7K for insertion of a turner engine, $10K if they had to rebuild), are these the bits I need to order?

I know there are kits to be had for all of this, but I wanted genuine parts if I'm going to do this.

[Snagger]

Ooh!  No, they’re not meant to do that! 😆

It could be a head gasket failed between a cylinder and an oilway (the push rod bores are also tasked with allowing oil to return from the head to the sump via the cam followers).  But it could also be cracked pistons or broken rings.  Hopefully it’s not damaged bores, but I suspect at that age, it’ll be pretty high mileage and they could be pretty worn.  I don’t think it could be just worn bores by themselves, though.

I think you may want to consider adding cam followers to the list, along with a timing kit (belt and tensioner).  Get valve stems caps too.  When you lift the rocker shaft off, you’ll be able to see if the rocker pads need refacing or the rockers need outright replacement.  The rocker shaft wears out too, so check for play once it’s off the head.

Turners will send you OEM parts much cheaper than you’d be able to buy LR Genuine Parts.

It could also be worth considering replacing the engine with a Tdi, if you can find a good one for a sensible price.  It seems crazy to spend that much money on something son asthmatic.

[evanmc]

Thanks for the pointers.

I've replaced the head gasket about 2 years ago and the timing belt about 5 years ago.  I suppose I could take the head off, and if the gasket was indeed failed, just replace that, and proceed with a rebuild if it does look OK. So how do I check for a worn bore?

Replacement TDi engines are not terribly common here, unfortunately, but I will check, certainly.

Turners was the only place I could find the pistons -- I suppose I could get all the other bits there.

-Evan-

[deep]

I thought mine was fumey but this is something much worse.  I'd suspect a broken piston.  Head off might give you a pointer but the sump will have to come off and the pistons removed.  It doesn't have to be all bad news.  If you only have to replace one cracked piston and the bore isn't damaged, the cost may be reasonable.

I guess it depends on the mileage you cover but I don't really subscribe to the rich man's notion of "replace everything while it's in bits", largely because I live on a tight budget.  If something's half worn, it still has half its life ahead of it and it's wasteful to throw that away!  Check everything carefully and replace anything suspect but you gain nothing by throwing a ton of money at it, unless it's a high pressure work vehicle in constant use (I'm sure it isn't).

[evanmc]

This was my daily driver until about a year ago, so now it's no big deal if it is in pieces in my garage for a while. Just have to finish up another truck project there to make room.

When you say "broken piston", what do you mean. and what am I looking for?  Just a crack in the piston?  Just trying to see how much I can do with just a head off that is no big deal, and how much must be engine out, that is.

I have not noticed a significant drop in power. BTW.

-Evan-

[steve b]

1 hour ago, evanmc said:

 

I have not noticed a significant drop in power. BTW.

-Evan-

get a head gasket kit and pop it off, it sounds like a blown HG . While off get it checked for straightness and maybe pressure tested for cracks .

Also check for bore wear , an obvious wear lip at the top at 90deg. to crank checked with a finger nail is a good initial check , if you want more accuracy get an internal micrometer and measure at 90 deg. opposite points as low as the piston will allow and at mid travel .

At 200k it will probably need a rebore to make the rebuild worthwhile , but a cheap check over and new HG will tell you plenty and give you time to decide .

cheers

Steve b

[Snagger]

These engines are generally understressed, unlike the turbo version that followed them (never adopted by the military for that reason), but they can still crack their pistons if they get hot.  My 12J would frequently get close to, but not into, the red on long hill climbs in summer, and descending the other side of the hill didn’t really bring the temperatures down, but dropping a gear to raise the revs rapidly dropped the temperature.  That problem went away with a replacement exhaust (correct 2” diameter instead of the old petrol exhaust - this was on a 109).  So, even without technically overheating the engine, you could have cracked the pistons.  You should see that if you remove the head and clean the pistons of soot with soft wire wool (brass rather than steel) or a Scotchbrite.  They generally crack across the piston left to right, not front to rear, and tend to be close to centreline.  Hopefully the bores are ok - they tend to last very well on these and Tdis.  Look for the honing pattern on the bores.  They’re likely to be a little worn, but if you can still see honing, they don’t need reboring unless you have a vertical score from some dirt or damaged pistons or rings.  A rehone can be done in situ with the ball/bog-brush type honing brushes common in the US.  Reboring is a professional shop job that needs a full engine strip, so fingers crossed it doesn’t need that.

The heads on these engines are pretty tough, but nothing is indestructible, so have a good look for cracks from around the valve seats and hot spots.  The hot spots are prone to cracking from their square corners (really, square corners are not a new engineering faux pas and they should have known better!), so if the cracks are significant or you have the common looseness of the hotspots in the head, it’s time for new.

Timing belts are good for 72,000 miles or seven years, whichever comes first, if I remember correctly.  I use 60,000 and five years, because they’re not that expensive but their failure is!  Don’t even think about rebuilding an engine and using an old belt!

For engine parts, I really wouldn’t go anywhere but Turner.  They’re good on prices without ever compromising standards.  It’s never worth getting the cheapest parts on engines or transmissions.

I’d also recommend opening the oil pump and checking for wear of the gears, idler shaft and pressure relief parts.  Renewing the spring and, if scored, the piston would be wise.

[monkie]

If it isn't your daily driver and you can accept it being off the road for some time, I wouldn't buy anything other than a gasket set (Elring head gasket) and a timing belt set. Take it apart and check how servicable each part is then produce a list of what you need based on careful  inspection of the parts. My engine is a 19J rather than the 12J, but here are some examples of what to look for in pistons and the head. Pistons 2 and 3 were cracked down the centre as Snagger says, you need to look carefully as they really are hairline cracks. The head had cracks between the valve seats and from a valve seat to combustion chamber.(Sorry for the poor quality of the photos - but hopefully you get the idea!)

The bores were actually in good condition, but check your piston rings crefully to make sure they are not stuck or gummed up.

 

[Snagger]

Haha! Those pistons aren’t cracked - on my 19J you could literally see daylight through the cracks! 😂

As Monkie says, the cracks tend to be hairline, and that’s why scrubbing the crowns helps, perhaps with a little fuel or solvent, so you get clean aluminium contrasting with the dirt in the crack.

[monkie]

7 minutes ago, Snagger said:

Haha! Those pistons aren’t cracked - on my 19J you could literally see daylight through the cracks! 😂

As Monkie says, the cracks tend to be hairline, and that’s why scrubbing the crowns helps, perhaps with a little fuel or solvent, so you get clean aluminium contrasting with the dirt in the crack.

How's this piston then for you? (the engine was amazingly still running quite nicely at tick over!)

 

[Snagger]

Haha! About the same as two of the pistons on the Chavalier I was using when I rebuilt the 109. It blew a head gasket on the way to East Midlands airport and I got there (just about) on two cylinders, lurching and bucking weakly.  It was an unloved temporary car to be scrapped on completion of the 109, so after the AA recovered me home at the end of the work duty, having pronounced death on the car (Conrad or crank, he reckoned), I opened it up, just threw a new head gasket in and pretended the pistons were fine.  It worked fine!

[paime]

13 minutes ago, monkie said:

How's this piston then for you? (the engine was amazingly still running quite nicely at tick over!)

 

What on earth caused that?? Marbles in the fuel mix??

[Snagger]

3 hours ago, paime said:

What on earth caused that?? Marbles in the fuel mix??

Looks like a dropped hotspot to me - notice the semicircular indentation at the apex of the V?  Hotspot probably dropped, did that, then got smashed and the debris did the rest of the crown.  I’d hate to see the valves and seats!  I’d be surprised if debris didn’t score the bore, too.

[paime]

At the risk of exposing my lack of knowledge...what's a hotspot?

[monkie]

I have no idea of who did what to this engine before I had it. What I can tell you is that the bore and head were fine. So someone either did a terrible job and put a damaged piston into the engine or something else did it. I still have this piston as a momento and when you look closely at it the damage looks more like cheese on toast; the surface looks more melted than hit. Possible cause bad injector spray causing the formation of hotspots on the crown?

4 minutes ago, paime said:

At the risk of exposing my lack of knowledge...what's a hotspot?

A hotspot in this sense is the swirl chamber part that is inserted into the head on indirect injection diesel engines. On a Tdi (or newer) the fuel injector sprays the diesel at a high enough pressure straight into the combustion chamber formed into the piston itself. On pre-tdi diesel which are indirect injection, the injection pressure is lower and so sprays the fuel into a combustion chamber in the head to give a smoother combustion. This is why the pre-Tdi engines are quieter and smoother running than the clatter from a Tdi.

That hole in the head is where a hot spot would sit and you see through the injector apature to the other side.

 

[paime]

Every day is a school day! So the actual combustion in pre-tdi engines takes place not in the bore but in a separate chamber?

[monkie]

The piston on the compression stroke pushes air through a small port into the combustion chamber, this causes it to swirl so when the fuel is injected into this swirling air it mixes well. The hot gasses then are forced back through the port in the chamber into the cylinder for the power stroke. The glow plug and injector sit in the combustion chamber rather than protruding the face of the cylinder head into the cylinder. 

[Snagger]

The hot spot is also known as a swirl chamber.  It’s not a combustion chamber - that is still in the bore- but some combustion will occur in there.  It’s a fancy injection port to get better atomisation of the fuel with lower pressure systems.  Direct injection gets good atomisation by having far higher fuel pressure delivered through finer jets straight into the cylinder.

[monkie]

37 minutes ago, Snagger said:

The hot spot is also known as a swirl chamber.  It’s not a combustion chamber - that is still in the bore- but some combustion will occur in there.  It’s a fancy injection port to get better atomisation of the fuel with lower pressure systems.  Direct injection gets good atomisation by having far higher fuel pressure delivered through finer jets straight into the cylinder.

Well, yes and no. I get your point but the fuel begins the combustion process in the swirl chamber before entering the cylinder. The combustion of diesel is near instant as soon as it mixes with the hot air in the swirl chamber. 

 

[evanmc]

I finally made room in the garage when I got my other truck out and started to take a look at this.  My first compression test showed really low compression on all cylinders.

From the front: 300 PSI, 180, 220, 240

I have not yet tried a leakdown test.

 

-Evan-

[evanmc]

I've made several mistakes here -- i used the wrong compression ratio (21:1 is what is in the manual), so figures are not as bad as I thought, but still not great, and and I did not test with a fully charged battery.

Just tested, and cylinder #4 is 320, not 240 with a charge and a squirt of oil.

-Evan-

[monkie]

To be honest when I do a compression test; I don't focus too much on the actual individual numbers but pay closer attention to (1) the difference between the cylinders (2) difference between the dry readings and the wet. 

Perform the test when the engine is warm and then review the dry and wet data. 

You are looking for consistency in the reproducibility of the data you collect here so perform a few readings, remove any outliers and average the numbers. 

[Eightpot]

You don't mention if the exhaust is smoking at all, if you're getting a constant haze you may have worn valve guide seals.  These are a very unstressed engine so I wouldn't be thinking cracked pistons etc myself but as its so quick to whip the head off, do that first and have a look for evidence of wear or damage on the bores, unusual clean areas or head gasket damage.   Put some light oil in the cylinders and see if it drains past the rings unusually quickly in each one.  

These engines always tended to suffer a lot from blow by, most of the ex military ones were fitted with a cyclonic breather rather than a straight through cap vent.

 

[lo-fi]

By-the-by: It's not just the 19J that suffers cracked pistons. An unlucky mate of mine had two 12J's in a row let go. The one in the vehicle originally had three pistons cracked; the "it's a low mileage minter, honest mate" replacement he obtained had suffered the same demise with all four. I suspect in the first instance it was timing or injector related as he could never get it to run right. The second one is anybody's guess.

If you're reading inconsistent compression between cylinders, it's time to take the head off regardless. Whatever you might need to do to rectify it will require access to valves, pistons or the gasket itself, so grab a decent gasket kit, get spannering and hope for the best would be my approach here. From the video, my money would be on cracked piston, broken rings or a serious gasket failure cylinder to an oil passage. 

[monkie]

👆What lo-fi says. Take the head off and inspect bores, head and piston crowns very carefully. Have a good look at the head gasket too before you discard it. Best case is a new head gasket (get a good one like Elring). Even if you need to replace a set of pistons its not the end of the world. Just take care to make measurements and observations as you go. What is the oil consumption like?