 |
| A 1990 Range Rover County @RobisonService |
At Robison Service we have been rebuilding Land Rover engines for 30+ years. We have been rebuilding original pushrod Land Rover V8 motors with flanged liners for a little more than ten of those years. The flanged liners address the problem of loose liners moving up and down – the flange clamps them positively in place. That was a problem that appeared in the late 1990; at the time people attributed it to worn out tooling.
If you've got a bad pushrod engine in your Land Rover you may want to start with this article on making the decision - repair or replace.
For a number of years Land Rover sold very inexpensive replacement blocks. That came to an end after 2008, when the last of the Discovery II models went out of warranty and the engine stocks ran out. That was when we and others began looking for an alternative, and settled on flanged liners in the existing blocks.
The flange provides an extension of the cylinder wall steel for the head gasket to seal against, preventing head gasket failures when liners move relative to the aluminum block. The flange also prevents coolant from migrating through cracks in the block, between the liner and block, and into the combustion chamber. In the same way, combustion gases are prevented from going the opposite way and pressurizing the cooling system – the principal mode of failure in original engines.
If you've got a bad pushrod engine in your Land Rover you may want to start with this article on making the decision - repair or replace.
For a number of years Land Rover sold very inexpensive replacement blocks. That came to an end after 2008, when the last of the Discovery II models went out of warranty and the engine stocks ran out. That was when we and others began looking for an alternative, and settled on flanged liners in the existing blocks.
The flange provides an extension of the cylinder wall steel for the head gasket to seal against, preventing head gasket failures when liners move relative to the aluminum block. The flange also prevents coolant from migrating through cracks in the block, between the liner and block, and into the combustion chamber. In the same way, combustion gases are prevented from going the opposite way and pressurizing the cooling system – the principal mode of failure in original engines.
The flanged liners have proven much more rugged in cases of other failures. Flange liner engines are much more likely to survive an overhead following a water pump failure, for example.
 |
| 40,000 miles later the liners and block look good (c) J E Robison Service |
In the past year we have begun seeing a new failure; one that all owners of pushrod V8 motors should be aware of. We’ve seen four engines in a row with combustion blowouts through the lower part of the head gasket. The gases blow out toward the exhaust manifold and are often confused for manifold leaks. There is no overheating associated with this, and no oil or coolant leakage. The middle cylinders tend to be the ones that fail. Prior to this, we have not seen a single rebuilt Land Rover engine failure of this type. It’s a new problem.
We have seen stock engines blow the head gaskets in this way, but blowouts in flanged liner rebuilds are a new thing.
The earlier Rover engines used metal head gaskets, and performance rebuilders still use metal. This problem may be limited to engines with the stock style composite gaskets, which were used from 1990 onward. The composite gaskets seal external coolant and oil leaks better, but are not as good at resisting combustion blowout. Their strength depends on clamping force (compression.)
We have seen stock engines blow the head gaskets in this way, but blowouts in flanged liner rebuilds are a new thing.
The earlier Rover engines used metal head gaskets, and performance rebuilders still use metal. This problem may be limited to engines with the stock style composite gaskets, which were used from 1990 onward. The composite gaskets seal external coolant and oil leaks better, but are not as good at resisting combustion blowout. Their strength depends on clamping force (compression.)
We have examined these engines very carefully to ascertain the reason for the failure. In each case the problem appeared 3-4 years after an uneventful overhaul. Miles run ranged from 20-45,000. We’ve done hundreds of these motors, so the failure rate is low, but still worrisome.
Our process for installing these liners is the same as ten years ago. What’s changed is that the blocks are older. There are more cracks and more corrosion. But we don’t think that is part of the problem here. Corrosion would put coolant into the oil, and we have yet to see that on any motor. Otherwise typical cracks don’t seem to have much effect on flange liner engines but a new effect remains a possibility.
The liners and machine work are under our control, so we can be sure they didn’t change. Like everyone else we buy head bolts and head gaskets from outside suppliers. We have long bemoaned the poor quality of many aftermarket parts and we use genuine gaskets to minimize risk, hoping they hold the best quality standards. The factory gaskets are made by Elring and look the same as the Elring kits sold in the aftermarket, with the addition of Land Rover logos. However we know looking the same and being the same are often two different things. That said, the head gaskets appear the same as years before.
Head bolts are different, and a known problem. The head bolts we got from the dealer used to torque up better than those from aftermarket suppliers. They felt stronger, and never broke on installation as cheaper ones sometimes did. Now the genuine head bolts have the same problems, and on each of these motors we found several loose head bolts. We think that is the problem – the bolts are stretching and the gaskets blow when the clamping force drops.
We have been repairing the motors with new head gaskets and ARP stud kits instead of bolts. The head nuts are torqued to a number instead of angle of rotation. We hope this solves the problem; time will tell. The photos below show the studs and their installation:
The studs have a coarse thread that goes into the block. The stud should screw in with just finger effort. If it takes more that's a sign the block is cracked or the threads are pulling out. The studs have an Allen nut in the center, and you use that to set them tight at the bottom.
Studs have been a standard for high performance motors for quite a while now. After these bolt problems we have decided to put studs in all our Rover engine builds.
When we do whole motors the engines are swung in assembled. On some Discovery models there is not enough clearance to take the heads on or off with studs in place, so you put the studs in after setting the head down, and remove them before taking them off. That is a good reason not to set them with Loctite; otherwise you will have to pull the engine!
The studs have a coarse thread that goes into the block. The stud should screw in with just finger effort. If it takes more that's a sign the block is cracked or the threads are pulling out. The studs have an Allen nut in the center, and you use that to set them tight at the bottom.
Studs have been a standard for high performance motors for quite a while now. After these bolt problems we have decided to put studs in all our Rover engine builds.
When we do whole motors the engines are swung in assembled. On some Discovery models there is not enough clearance to take the heads on or off with studs in place, so you put the studs in after setting the head down, and remove them before taking them off. That is a good reason not to set them with Loctite; otherwise you will have to pull the engine!
Some readers point out that head gasket blowouts are not unknown on regular Land Rover V8 motors. That's true . . . we see that too. However, the flange liner engines have up to now resisted this failure. We think the flanges help hold torque better.
The moral of that story is that you have to be ever vigilant to be successful with these vehicles. These are simple motors that went out of production 15 years ago, but there are still thousands of them on the road and we’ve got five in the shop right now for overhaul work. It’s clear they will be around quite a few more years and we need to stay on top of them.
The photos below show what’s going on:
The photos above show a blown head gasket. The slit is where combustion gases burned through the fire ring. The photo below shows the block on a motor where this happened. If you repair this problem promptly the block won't be damaged, but if they drive it a long way the block will be eroded, and you will have a very expensive repair.
The information in this story is provided as-is, with no warranty or guarantee expressed or implied. As always, if you have a failed engine. do a careful evaluation, consult a qualified expert, and make your best decision based on the facts of you motor and what you can learn.
This article applies to the pushrod V8 engines used in Land Rover Defender, Range Rover, and Discovery from 1983 to 2004. Search the blog index for my earlier articles on these motors.
© 2019 John Elder Robison
John Elder Robison is the general manager of J E Robison Service Company, celebrating 30 years of independent Bentley, Rolls-Royce, BMW/MINI, Mercedes, and Land Rover restoration and repair in Springfield, Massachusetts. John is a longtime technical consultant to the car clubs, and he’s owned and restored many fine British and German motorcars. Find him online at www.robisonservice.com or in the real world at 413-785-1665
Reading this article will make you smarter, especially when it comes to car stuff. So it's good for you. But don't take that too far - printing and eating it will probably make you sick.
Posts
No comments:
Post a Comment