Thursday, February 20, 2014

Blown Head Gaskets on Land Rover V8 Engines

I've got a blown head gasket in my Land Rover.  What will it take to fix it?  That's a question Land Rover service managers hear fairly regularly.  We used to do head gasket jobs all the time, but in the last 5-7 years many of those jobs went bad. Many shops won't even do LR valve jobs anymore.  Why?

This is a big issue for people with the original LR-Buick aluminum V8 engine - all the US market Defenders and Range Rovers to 2002 and Discovery I and II models through 2004.




The engines overheated and failed either right after the head gasket job, or within a few months.  At first I thought the failures were comebacks - errors of workmanship.  But I soon realized the problem was not the workmanship - it was the motors themselves.  They were failing internally, in seemingly invisible ways.

Join me now as we look closely at a seemingly simple head gasket failure, and find there is much more to the story . . . 

This 2001 truck came into Robison Service a few days ago (early 2014) with a noise complaint.  Exhaust gases were blowing out between the head and the block.  It seemed like a classic case of fire ring failure in the head gasket.  In years past, I'd have been right on it with new head gaskets and a cleaned up heads.  Today, not so quick . . . As it happens, our caution turned out to be well founded.

Here are both heads off the motor.  As clearly shown, only one has a blowout (second cylinder from the left, upper head)  So far, it looks like a blown gasket.






OK, now lets look at a closeup of the failed cylinder in that upper head.  The blowout line is in the center.  Look at the holes for the head bolts.  The one on the left is actually facing the front of the engine, as you are seeing the head upside down (we will look at that hole in the block in a minute)   Note how its orange from coolant intrusion.  The one on the right (the rear bolt hole) is clear and that’s what you want to see.

The orange is sedimented Dex-cool.  Sedimentation is a known issue with Dex cool and it's particularly visible here.  It looks very different from freshly spilled coolant, like you get from teardown.  Scroll down the page four more images and you'll see freshly spilled coolant in a head bolt hole.  There's no mistaking the difference.

There are some motors where the head bolt holes go into the coolant galleries.  This isn't one of them.  These holes should be dry.  The fact that they are not suggests a crack or leak somewhere.

The blowout has damaged the head slightly but it's nothing we can't fix with a weld and resurfacing before the valve job.  Right now, that is the least of our worries.



Like I said, that dried coolant is a bad sign.  There are no coolant passages from block to head in the middle cylinders of a Rover-Buick V8.  There is no connection between the head bolt holes and the coolant galleries in the block, either. That area should never show coolant.  It's a bad sign, suggestive of internal failure.  But there's more . . . 

Now lets look at the block on the right side.




The blowout is clearly visible in the bottom of the second cylinder back.  Note the rectangular marks at the left and right edges of the block.  Those are the passages through which coolant flows into and out of the head.  There is no coolant flow through the middle.

The reddish spotting between 1-2 and 3-4 cylinders and the respective lower head bolt holes is even more suggestive of slow coolant leakage.  We will look at that in closeups.  When you look at the second and fourth head bolt holes from the left, those are dark.  The other holes are light, meaning no long term coolant intrusion.

This is a closeup of the lower head bolt hole and the edges of cylinders 1-2 on that side.  Note the pattern of leakage from the liners in toward the head bolt hole. See the “burnt” coolant in the bolt hole.  Those are sings of long term seepage.  This usually indicates a crack emanating from the bolt hole out to the liner faces on 1-2.  Also note the pattern of leakage continues onto the surface of the front piston, which is washed clean of carbon in the same area.  This is a sign of coolant intrusion into the cylinder and its location corresponds to the seepage on the block



For comparison here are the front and rear head bolt holes with a view up to the coolant passages from block to head.  In the rear one you clearly see some coolant leaked in disassembly and the difference between that and what’s dried and hardened in those inner bolt holes in the earlier images  is clear




Here is a top view of the blown head gasket.   There's no damage (other than the blowout) between this gasket and the head.  It's very clean and normal looking.



Closeup of the bottom reveals a different story on the engine block side.  That face makes the leakage pattern strikingly clear, and shows it’s all coming out of the block.  That's not surprising, because it can't come from the head.  There's no coolant in that area!  However, the area between the head bolt bore and the cylinder edges is hollowed out in the casting, for coolant flow.  That is the area that is vulnerable to cracking, and that's what's cracked in this motor.



The leakage traces on the bottom side of the head gasket really tell the story.  The way the gasket is discolored we know the leak has been developing over a long period of time.  What happens is that the crack grows, and as it does, the crack opening relieves the tension on the head bolt. That's probably one of the reasons the fire ring seal blew out.



Here’s a broader view of the bottom of the gasket, where two leaks are visible, to the left and right of the blown fire ring..  

Like I said, five years ago I'd have put head gaskets on this motor and sent it down the road.  And looking at today's evidence - it would have failed because the block was already damaged.  Head gasket leakage was a symptom of that failure, not the actual problem.  It may have lasted a week; it may have lasted six months.  Either way, it would have blown.

Here's a photo of a stripped engine block, after we cut it in half and circled the crack that made it fail.  The coolant passages are clearly visible


What do we do now?

The correct fix will involve removal of the liners, welding the cracks, and then fitting liners with flanges at the top, so that the liners will seal agains the head basket and coolant will not be able to go between block and liner and cause a blowout.

Read more about that in this article from 2012.

As a footnote to this story, when told about these issues, the owner of the truck told me he'd been adding coolant for a while for a period of months.  Now we know where it was going.  The coolant was getting burned in the cylinders as it leaked from the cracks behind the liners.  The fire ring blew out because the block cracks caused the head bolts to lose their clamping force.  We have an explanation for the whole thing, disagreeable as it may be to the one who has to pay the bill.  Still, I contend it's better to know the bad news up front than to discover it after a $3,000 valve job and head repair goes bad.


John Elder Robison is the manager of J E Robison Service, independent Land Rover specialists in Springfield, MA.  Find him online at www.robisonservice.com or on the phone at 413-785-1665

4 comments:

Scott Gaynor said...

Great write up. Thanks, John.

Some questions -

Why do you think these cracked blocks are becoming more prevalent?

Is the cost of repairing the cracks worth it vs. R&R the engine? Considering...

Do you think cracks would form elsewhere in the block, thus causing another faillure?

Superladies said...

Thank You for sharing such a useful post. Its very difficult to manitain a car in condition.

Sara Stout said...

I have a 1989 Toyota Celeca and have over the course of the last 5 years blown my head gasket twice. I don't know if it is faulty equipment or the way I drive. I know my spouse would greatly appreciate it if I could find out why this is happening and not have to spend the money to replace the head gasket every other year.

Zachary Stewart said...

That's solid mechanical investigation.

Does this mean that ALL of these engines have this problem? Or just the "lemons"?

I had a 1997 Discovery I with 175k on the original engine. But I've seen a lot of the Disco IIs blowing head gaskets at 90k miles.