Sunday, April 18, 2010

The last word on Land Rover liner failures - I hope!

Note:  This story was written a few years ago, but it's even more true today.  Robison Service is building 4.0, 4.6, and oversize Land Rover engines using the latest flanged liner technology.  Call us at 413-785-1665 or write robisosn at robisonservice.com if you'd like to talk about YOUR engine project.

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I have written several articles over the years, describing the liner problems in Land Rover V8 engines. No matter what I write, the damn engines continue to fail. And we’re seeing more and more of a pattern. These engines are, as best I can tell, failing more frequently than before, especially in the last of the Discovery II rigs. Where earlier motors tended to fail on end cylinders, these motors are blowing out the middle cylinders. That led us to wonder . . . is there a new problem in these late engines?

Last week we decided to find out.

We just got a new CO2 laser up here, and our machinist Steve Dutcher was looking for some action on a lazy Friday afternoon. Some people would go fishing, or even weasel hunting, but Steve had other ideas. He cut a Land Rover engine block in half, just because it was there.

When he did, we finally got some hard answers to what’s going wrong in these motors.

Let’s begin by looking at a brand new Land Rover short block. You might call this the “pre-failure” picture:



In this shot you see the aluminum block, with steel liners, and aluminum pistons. As you can see, the steel liners are tapered at the top, sort of like you’d bore a countersink hole if the engine block were a piece of wood. . . .



Now lets jump to the late model block Steve cut in half. He removed the liners before cutting this block right through the middle of the third cylinder bank. Check it out:



This block had a middle cylinder failure. There was no visible problem with the liner but it failed a pressure test on the middle cylinder. When we took the liner out, we found the crack you see circled here. Take note of what a subtle defect this is . . . you can barely even see the crack, but it’s enough to kill the motor. Here’s a closeup of the 1/4 inch crack that cooked this block.



The block cracked from the liner wall into the coolant jacket from the stress of the head bolt. Here’s a shot of the deck that shows that relationship. In fact, if you look close, you can see how the depth of the crack corresponds to the depth the head bolt is threaded into.



Here's a closer view, with my finger for perspective. The blue circled crack is visible to the left of my fingernail



Here’s another interesting shot. In this image you can see the step that prevents the liner from sliding down into the crankcase on these newer motors. In this design, the liner can’t actually move more than a few thousandths of an inch unless they failed to seat it against the step at the factory. What does that mean? It means the stories of "slipped liners" in these newer engines are probably incorrect. The issue is not movement of the liner (which can't happen in this example) but a failure of the block wall behind the liner.



This shot shows that post-2000 model year liners can’t move very much at all but the engines fail anyway. What gives? A little bit of thought gave us some answers.

The liner is tapered at the top where it meets the head and head gasket. For that reason there is no gas or pressure tight seal between the liner and the block. Therefore, when the cylinder fires, some combustion gas gets behind the liner. If there’s a crack back there, out it goes and you know what happens next.

Your coolant gets displaced by superhot combustion gases, the engine temperature skyrockets, and in the blink of an eye, your Rover is assuming the British Position on the back of a tow truck. And you are facing a ten thousand dollar repair bill.

How do these failures happen? It sure looks like the stress from the head bolts is causing the blocks to crack. I don’t know why this is happening now; the aluminum may be more brittle, or the head bolts may be stiffer. Perhaps longer or shorter bolts would help.

Now that we know what’s happening, it’s clear that top hat liners will fix this problem once and for all, even in an engine with cracks in the aluminum. The flanges on top of the liner will seal tight against the head gasket, preventing any combustion gas from getting between the liner and the block and blowing things up.

This picture shows the difference. The left cylinder has the original liner. The right cylinder has a top hat liner, which cannot move in the block. In addition, the head gasket now seals against the liner for a firmer and more positive combustion seal.



Why doesn’t Land Rover use flanged liners? My guess is, they cost a few dollars more and carmakers are notoriously cheap. It’s also possible that there’s an issue with the steel liner expanding at a different rate than the aluminum block and heads.

How about the engines that rap at idle? I’ve had several late model Discos at the shop with noise complaints. In two cases, dealers told the drivers they had noise from liners moving up and down, and they suggested the motor was about to fail as a result. One dealer actually got the motor hot and heard it rap, at which time he sprayed the side of the block with a hose and the rap went away. He told the customer that was evidence of liner movement.

Actually, it wasn’t. These photos make it pretty clear that late model liners have nowhere to move. The hose test simply showed that the noise went away when the engine block was cooled – in other words, the noise was triggered by thermal expansion.

Steve and I sorted that noise question out on another engine a few months back. On that motor – which had exactly the same hot rap – we found the piston skirts had collapsed in about ten thousandths of an inch. That was enough to make them rock when they got hot, and they rapped good and loud.

On that engine we expanded the piston skirts and refitted the pistons. No more rap. But did that repair need to be done? Loose piston skirts would not lead to a failure. I’ll bet that motor would have run 25,000 miles with that rap, maybe a lot longer. In any case, new pistons are the fix. Liners are not involved at all, unless the block were to crack when the head bolts were cinched down one more time . . .

While were talking noises . . we saw a few engines whose secondary air valves had failed, and they also rapped. If you didn't know better you'd swear that secondardy air rap was coming from within the motor. And we still see engines with rocker shaft issues and lifter issues where the raps will fade in and out as the parts rotate while the engine idles hot.

I’m glad we’ve finally got some positive answers about these latest failures. When we rebuild engines here, I’m thinking we need to do flanged liners in the middle cylinders, and maybe all eight cylinders. The only drawback to that is going to be cost – it’s going to make the cost of redoing an old block almost as much as the $5,000 cost of a new one. But if the flanged liners last and the factory ones fail, that’s still smart money.

Like everything else, time will tell . . .

And one more thing before I go. In October I wrote about some later blocks that failed from premature corrosion. Here's a view of the freeze plugs on this motor. As you can see, they are pretty rotted but the aluminum block itself is good. Check your freeze plugs if you do an overhaul. It would suck to lose it all for a two dollar metal disc.

Friday, April 9, 2010

The Bentleys are coming!




It’s spring in New England. Now that the snow is gone, the Rolls Royces and Bentleys are coming out of the woodwork.

I’d like you to meet one of my old friends and his car:



This is Efrem Gordon, a local attorney and long time Bentley driver. One of my judge buddies describes Efrem as the elder statesman of the Western Massachusetts bar. He graduated Harvard Law School before I was born, and he’s practiced here in Springfield ever since.

For a quarter of a century, if I had bad trouble, I always knew I could turn to Efrem for help. For just as long, we’ve kept these cars of his running.

Here are a few views of the car . . .






This Bentley R Type is just about all original. It's got less than 50,000 miles on the odometer, and it still works like new.