New Head gasket or new motor? 2005 Volvo S60R

[BlackBart]

General question - Can a leak down test determine the difference between a valve seat, a head gasket, or a cracked sleeve leaking pressure?


<EDIT> If the piston is at top dead center for a leak down, it may too high to expose the sleeve crack. Where do the cracks usually form?

[- Pete -]

The cracks appear at the top, between adjacent cylinders.

[humanatek]

UPDATE:

I've decided to pay to have the head removed so we can further investigate what may have caused the head gasket failure.

My best educated guess is that my leaking exhaust/turbo down pipe may have finally burned out my head-gasket and finally caused the leak. I'll know by next week. If this is what caused it, then I'll be keeping the motor and just rebuilding the head and replacing the gaskets and maybe getting a monosleeve... I'll probably also get an upgraded turbo.

Besides Viva Volvo's is there another place to get a fair price on a monosleeve for an S60R?

[RickHaleParker]

Besides Viva Volvo's is there another place to get a fair price on a monosleeve for an S60R?

Darton Sleeves is in Carlsbad, CA You might want to contact them directly and see what they can do for you, or go through the distributors list for somebody close to you.

[SuperHerman]

Leak down test - explanation - air is forced into the cylinder when the valves are closed (usually at the top of the stroke).

As air is pressurized it looks for away out. Possibilities for air to escape are: 1) cracked cylinder walls, head gasket that has been compromised, piston rings, intake and exhaust valves and spark plug adapter (or area).

All engines leak somewhat - main place is the piston rings. Tight rings leak at a certain "acceptable" level while worn rings leak at a greater rate. Valves leak when they are carboned up, compromised (either valve or valve seat), or are bent. Head gasket leaks when it is blown and the air escapes into the next cylinder(s). The same holds for the cylinder walls, but your concern has some merit. First the engine is cold and the cracks may not be large enough and second not enough of the crack may be exposed if it is located down past the rings.

Before moving forward - listening for air leaks is the main test - a hiss from the left/front or right/back tells you exhaust or intake (varies with engine). For the Volvo the exhaust is generally on the back. Comparing with other cylinders also provides useful information.

That said the pressurized air will pass through even though the piston is at TDC because the piston and cylinder are not a 100% fit by design. The piston rings are as close to 100% as possible less ring gap, but they are elastic by design and simple physics (otherwise they would be frozen in place). Piston rings are can be seen as round springs pushing out and riding on a layer of oil. They are larger then the piston, but smaller than the cylinder (ring gap). In a normal situation at TDC the air will go to the rings and bleed/leak through. So they will travel the distance of the piston tops to the piston rings - this distance varies by engine but on every Volvo I have worked on at least 1/2" - being conservative.

Based on the other poster's response that the cracks are up high - my guess is the cracks will come into play on the readings, but could be lost by the piston ring factor.

So to answer your question - a leak down test may give additional clues, but only when compared to all the other cylinders. This of course assumes the other cylinders are in the same basic condition.

[BlackBart]

Great explanation - thanks.

I've always wondered - if you're listening for hissing out the intake or exhaust, and it's a head gasket and the leak is going across to the next cylinder, aren't you getting the same sound? I imagine the neighboring cylinder has a valve open and that would tell you something different. Or is the head gasket leak unlikely to go all the way to the next cylinder, and you're more likely getting bubbling in the coolant?

[SuperHerman]

BlackBart - all of your wondering is correct. The problem is it is very hard to tell when the leak is extremely small. Even worse when the engine is cold.

One has to look for visual clues like clean piston tops and spark plugs for example while comparing the various cylinders and known good values.

If the leak is large enough to hiss through another cylinder these clues will be apparent.

I also thought about bubbling of the coolant, but I am unsure if it can be noted on a small leak, especially with a cold engine. Heat expansion enlarges failure points.

A block test, using fluid, to find combustion product in the coolant is another tool.

Several years ago I had an 2004 S80 2.9 which I bought with a blown head gasket. It had about 80k miles if I recall. Looking at the service history it went to the dealer and received a water pump, and various other items under warranty. Later invoices from non-dealer shops kept at the problem but never found a solution - various parts thrown at it. As the dealer involved is pretty solid and the shops the same I would imagine they did all sorts of tests, but could never find the culprit for the consistent and slow loss of coolant.

When I got it the engine ran, but the oil was a milk shake and it was a smoker. When I pulled the head it was clear the head gasket was the issue all along. Looking at the plugs and piston tops showed steam cleaning. The head gasket showed a small but discernable failure consistent with the visual findings. My guess is the head gasket was defective, possibly installed incorrectly, or maybe something was introduced like a foreign object (tiny metal shaving maybe) during assembly. The issue was kicked around under warranty and then out until it completely failed.

So your wondering has merit.