Head Gasket Fix and Bad Gas Mileage

[bleslie]

Hello,

I unfortunately had to have a head gasket job about three weeks ago. The job was done by a certified land rover mechanic and i know they did a good job, but ever since i have had the rover back my gas mileage sucks. I was getting 350+ miles to the gallon, and now only 300. Basically about a 2 mpg loss. There is also a tapping noise that i can mainly only hear inside the cabin when the engine is warm. Any ideas on why my mileage dropped and also the tapping noise? Thanks in advance. Blake

 

[joey]

Mileage may have dropped due to the ethanol in the fuel due to winter months... it usually goes up and the fuel economy goes down.

 

[Disco Mike]

I am not sure how you can say,"You know they did a good job", when your mileage has fallen off and you now have an internal noise.
I would get it back to them Today and see what is wrong.

 

[deeb]

Hello,

I unfortunately had to have a head gasket job about three weeks ago. The job was done by a certified land rover mechanic and i know they did a good job, but ever since i have had the rover back my gas mileage sucks. I was getting 350+ miles to the gallon, and now only 300. Basically about a 2 mpg loss. There is also a tapping noise that i can mainly only hear inside the cabin when the engine is warm. Any ideas on why my mileage dropped and also the tapping noise? Thanks in advance. Blake

excuse my nosy-ness, but how much did you pay for the head gasket job? was it done on both sides or just one?

im on the brink of the same thing and curious what im in for.

thanks
chad

 

[Chongo]

Head Gasket Fix and Bad Gas Mileage

Hello,

I unfortunately had to have a head gasket job about three weeks ago. The job was done by a certified land rover mechanic and i know they did a good job, but ever since i have had the rover back my gas mileage sucks. I was getting 350+ miles to the gallon, and now only 300. Basically about a 2 mpg loss. There is also a tapping noise that i can mainly only hear inside the cabin when the engine is warm. Any ideas on why my mileage dropped and also the tapping noise? Thanks in advance. Blake


Well, if I’m reading this right, you were getting 350 mpg, and after the head job was finished, you’re getting around 300 mpg with a 2 mpg loss.

I did the math, a got a 50 mpg difference instead of 2, and if you’re getting around 300 mpg you’re awesome, and you have total bragging rights over any Hybrid………………. I’m surprised no one caught that……..lol

That knocking noise is most likely the liner moving 004” believe it or not. You definitely need to document this and get this dealers attention to fix this properly. Please read below.
Engine

The engine in the disco 2 is the old buick 215 v-8, with no roller cam, and no rotators on the exhaust valves like US engines. The dry cylinder sleeves, “ these are not wet sleeved engines”, are straight, un - flanged and made of steel, while your block is made of aluminum. This creates a thermal condition of dissimilar materials. Many mechanics blame a blown head gasket on this thermal condition as a, “dropped liner”, but in reality at about 210 degrees operating temperature the cylinder liner actually moves around .004” of an inch away from the head gasket ring , this releases the tension on the head gasket between the liner and the head. This also releases the tension between the head and the head gasket between the liner and the head, and reduces the heat sink value on the head gasket steel ring, {this is why when you remove the old head gaskets on a land rover the steel ring on the head gasket is usually yellowish or has a burnished color}, causing premature head gasket failure. Now note what I said, the head to liner distance is getting larger by .004” not the head separating from the block, but the liner actually grows 50% shorter than the aluminum block walls. And since the stock land rover liners seat at the bottom of the bore, and on the main bearing saddles the expansion ratio starts at where it seats, at the bottom of the bore, not the top.
Expansion ratio of steel is 6 parts per million per degree
Expansion ratio of aluminum is 12 parts per million per degree.
No real such thing as a dropped liner according to popular belief, it is a thermal problem with dissimilar materials. And there is only one bullet proof cure, Top flanged liners, sometimes called top hat liners in the British market.
There just isn’t any other long term substitute for this issue.

Cracked blocks

A rare issue

Land Rover Bosch engine blocks, or the old buick 215 block usually cracks on the main bear saddle bulkheads, just below the liner. This is caused by the straight walled liner. Since the straight walled liner has no lip or flange at the top of the bore to seat against, it must seat against the bottom of the bore. Where the crankshafts main bearing saddle bulkheads hold all the tension from the tightening of the cylinder head bolts. As you tighten the head bolts, the head is pushed towards the block, pushing the steal ring head gasket towards the cylinder liner, forcing the liner to push hard against the bottom of the bore in the block, which is the main bearing saddle bulkhead. Switching to top flanged liners eliminates this issue. This is a rare issue, but I have seen this
several times in my lifetime with this engine.

Head Bolts

Head bolts must be replaced every time you remove the head, they are not regular bolts, but a special designed stretch bolt. Their is a tightening sequence principle that must be followed although contrary to popular belief, and the service manual, as long as the principle is adhered to the sequence can be changed. The principle is uniformly and incrementally tightening the head down. The actual order doesn’t matter.
Take a good look
how the head gasket is designed and it comes with a sticky adhesive on the
composite part of the gasket. This will work beautiful if both surfaces are left
perfectly dry, and free of oil, i.e. lacquer thinner. Use NO OIL PERIOD on the head bolts, You’ll regret it if you do. You see the oil you put on the threads, like the book tells us to, will push off the threads as you thread it into the threads of the block and it
gets between the block and head pushing into the gasket areas ruining the effects of
the adhesive on the gasket, Oil and adheasive isn't usually a good combination......

What I did and this works well, I put only 2 layers of Teflon Tape on the threads of the new head bolts and a small amount of grease just under The bolt head. What this does is not let the bolt head gall into the heads and lubes The threads into the block without any oil. I believe this is an area where a lot of people have got themselves into trouble, and they followed the book. This would probably cause gasket failure in a few thousand Miles or so, and would probably be blamed on the mechanic or machinist, when it is A procedure problem. Use the Teflon tape on the bolts, it runs in nicely and life Is good.

In testing the book vs. torque standards I found the service manual, “again” in error as it says to tighten all bolts to 15 ft. lbs. then 90 degrees more in sequence, then a additional 90 degrees for final torque. This is bogus, and utter nonsense. My findings after doing this left the 3 long head bolts at 50 - 58 foot pounds of torque, while the short head bolts read 68 - 72 foot pounds of torque. I found that almost an additional 90 degrees was required on the long bolts for a total of 245 - 270 degrees before the long bolts achieved the 68 - 72 foot pound equivalent to the short bolts. This makes the tension and torque on all bolts even.
Due to the dissimilar materials of the steel bolts and aluminum heads it needs a stretch bolt design. Don’t go buying studs for this engine, you won’t be happy with the long term effects.

Best wishes……..Chongo