Head gasket failed. Any ideas? Pics included

[RXV550ME]

Hi, just wondering if anyone has an idea why my front headgasket failed? I torqued to factory spec but my guess is i may have over torqued. Replaced them when i pulled the heads off 700klms ago to do inlet valves. Ran well until last week when it started using water. A little water is in the oil but not alot. I also put a new set of rings in when the heads were off and replaced the o-rings at the bottom of the cylinders. It looks like i have put alot of sealent around the timing chain area but i only put on a very thin film. Can prob use less next time.
Cheers

[kimzx1000r]

http://forums.pstuning.com/blog/jim_hubert/index.php

Look here at the end of the of the posts may provide direction??

[ETN550]

The last 2 pictures look like you have a leakage path at 8:00 O'Clock. Check the head, liner and crankcase deck for flatness. Once a leak starts and it gets very hot from combustion gasses it could warp more.

Looks like a lot of sealant but the bead of the gasket was contacting all around so that may not be a problem.

[FORZA]

Lap the liner deck face & check for high/low spots.

Dave Ward
Moto Italia
Aprilia-Ducati-Moto Guzzi
0432 441 985

[amauri]

Some observations, please refference my red marks on your photos and previously posted Aprilia bulletin about head gaskets and new castings.

1st photo is an 07 or early 08 crankcase.
2nd photo is that of a late 08 cyl head
3rd photo is also late cyl head gasket

Though I don't think it is a problem, interesting none the less.

ETN550 is right about the area where it looks to be leaking, but IMO it is not a warped surface.

In this example, your leak is caused by the cyl sleeve sitting even or below the deck of the crankcase. Not enough protrusion as we've discussed here:
http://www.apriliaforum.com/forums/s...d.php?t=186941

[RXV550ME]

Thanks for the info everyone. The engine and heads are both 06 as far as i know. It went in for a reseal in early 07 but there was no mention of new heads going on it. What are my options here? Use a stone?
Any info appreciated.

[amauri]

What are my options here? Use a stone?
Any info appreciated.

Before you can dicide how to fix it, you need to measure the exact height of the cyl sleeves in the crankcase.

I believe Jim Hubert described how to do that in his blog linked in Kimzx post above.

[nicogc]

if i uderstand it correctly amauri is saying that the problem you have is that your sleeve is too low, so lapping it would not work. what you would have to do is shim it(if it is possible) or get a new sleeve? or is there another fix?

very informative thread. thanks!!!

[amauri]

The sleeves are made by Gilardoni and in my experience, very consistent.
A new one will not fix it either.

All 550 sleeves I've measured to date are exactly the same height, 1.981". Used or new.

You need to measure accurately to determine if too low or too high.
Use an outside micrometer on the sleeve and a depth mic on the crankcase.

Another equally accurate option is to use a precision ground steel bar and feeler gauges.

[irie]

This is such a good informative thread. Jim Hubert was right on the money.

If the crankcase is ground too short then the cylinder liner butts too hard into the head gasket and can cause leakage in the cylinder head. This can be corrected by using a slightly smaller thickness 'O' ring. And vice versa of course.

IIRC the standard cylinder liner 'O' ring is BS152 which is 82.22mm x 2.62mm (Viton of course).

I also seem to recall that some Renault car engines used 'O' ring cylinder liners - the Renault 16 perhaps? I think there were also problems with them ... but no doubt someone will correct me ...

[amauri]

This can be corrected by using a slightly smaller thickness 'O' ring. And vice versa of course.

Almost but not quite.

The lower flange of the sleeve bottoms out flat onto the lower step of the crankcase bore.
The sleeve and case are a metal to metal fit.

The o-ring does not determine if the sleeve sits lower or higher in the crankcase, it's only function is to seal. It is not a spacer.

[irie]

Almost but not quite.

The lower flange of the sleeve bottoms out flat onto the lower step of the crankcase bore.
The sleeve and case are a metal to metal fit.

The o-ring does not determine if the sleeve sits lower or higher in the crankcase, it's only function is to seal. It is not a spacer.

I know it's 'almost but not quite', but a 3mm metric 'O' ring solved the problem.

[amauri]

I don't doubt that the thicker o-ring fixed a water leak for you, but it will not raise a cylinder that is sitting too low in the deck.
Which in this case is causing combustion pressure to leak past the head gasket and into the water jacket (as we can see from the photos originally posted).

At the risk of starting another heated debate, lets just think about this for a minute.

If the bottom of the cylinder was sitting on a rubber o-ring instead of solid metal, what are the chances that there is enough pressure applied to the top of the cylinder for it to compress the metal head gasket when you torque the head?

[nicogc]

ok, but if it is determined that the cylinder is sitting too low, and the oring is not the right fix, then what would be the right fix? or what could we use as shims to raise the cylinder?
if it is too high then grinding can be acomplished easilly i think.

thanks.

[irie]

I don't doubt that the thicker o-ring fixed a water leak for you, but it will not raise a cylinder that is sitting too low in the deck.
Which in this case is causing combustion pressure to leak past the head gasket and into the water jacket (as we can see from the photos originally posted).

At the risk of starting another heated debate, lets just think about this for a minute.

If the bottom of the cylinder was sitting on a rubber o-ring instead of solid metal, what are the chances that there is enough pressure applied to the top of the cylinder for it to compress the metal head gasket when you torque the head?

I get your point, but if the cylinder lining is not sitting on solid metal, then what? We're talking about an April '06 engine here.