I purchased a certified pre-owned 2007 XC90 with 21K miles on it from a local volvo dealer back in March of this year. I have so far had to bring it in twice with a ticking noise coming from the engine. The first time they said it was the Tappet on one of the valves and it was replaced. About 3 weeks later I heard the noise again. They said it was the same valve, but the tappet wasnt the issue. They said the valve spring was too strong causing the tappet to misbehave. I have 2 quesitons....
1) Shouldnt the tech. have discovered the spring issue the first time I took it in for the noise? Or while testing it after they replaced the tappet?
2) Shouldnt they have ran some diagnostics during the "Volvo Certified Pre Owned 130 Point Inspection"? I mean springs dont tend to get stronger with use.. they get weaker right?
Thanks in advance for all your help.

 

Question #1: No. They don't remove and test valve springs as part of a CPO inspection, I'd wager. That's way too labor intensive. Valve springs don't usually fail unless you really, really like the red zones of tachometers. And with rev limiters, even those opportunites are few and far between unless you get the truck airborne from time to time with your foot to the floorboard.

Question #2: Yes. Springs get weaker, not stronger. Have you compared the tick, tick, tick to others with the same engine? Is it isolated to one cylinder (use a short piece of garden hose as a "mechanic's steathscope" to see if the sound is isolated to one valve).

Question #3: Maybe. Was the CEL on? If not, there's be no code indicating misfire or anything, so the tech simply wouldn't look. The tappet was heard, I assume. And its a reasonable assumption that a tick, tick, tick is a tappet noise.

Ask, politely, if there might not be something wrong now with the valve seat, too, as something is obviously wrong with the valve assembly. See what sort of reaction you get. Hey, the dealer doesn't care as long as Volvo pays.

TIck, tick, tick??? I hope your Volvo isn't a gray market import from Iraq or Afghanistan or someplace like that. If so, the problem might not be valve clatter after all......

 

malaka, thanks for the reply. The valve spring didnt fail. If I remember the tech said it was "too strong" and causing the tappet to misfunction. The CEL wasnt on. However I did notice that there was one time I was going about 75, gunned it to pass someone and got an error message. Something about "Downshift or slow down". Maybe the valve spring replacement will fix that. Its still in the shop, when they call I'll ask about the valve seat.

 

Valve springs don't get stronger and I don't think that's the problem. Also there is no way a tech would check a valve spring during a CPO inspection. They are more likely to check cupholders and wiper blades. My advice is to keep making the dealer try to fix it. If they can't fix it, call Volvo directly. You'll either get a new engine, or a new car under the lemon law. I've seen both.

 

I figured every noise it makes, I'll bring it back since its still under warranty.
Still havent gotten the SUV back yet. Part is on its way. Thanks all for your replies.

 

If the valve spring is too strong it cause excessive wear on the cam. If it is too weak then the valve will not fully close, or at least will not close quickly enough. In a highly tuned engine you cannot afford to skimp on the selection of valve springs. If one of these breaks then the valve will stick open and this will cause catastrophic engine damage, depending on which part of the suck,bang, blow cycle the engine is at.

The springs also prevent bounce. When the valve is pulled back into its closed position the last thing you want is for it to bounce open again as it closes.

If a spring is compressed and each coil is in contact with the coils above and below you have what is known as coil bind. The spring is extremely stressed at this bind point and you should ensure that you do not approach this bind point otherwise the cam lobes, lifters and follows will be damaged.
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Valve springs and installed height.
All those with two-strokes skip one page, but don’t smirk, check your reeds and clean your exhausts out with a small tissue.

We all need to replace valve springs on an ongoing basis if we want best performance.
Failing to replace springs when it becomes necessary can allow valve bounce to occur before maximum revs are reached, and in extreme conditions, big damage.

So when should you replace valve springs?
All workshop manuals give measurements of new springs, easy to do a comparison whilst the head/s is/are off and everything is stripped. Keeping a record of kilometres travelled to measurements taken from new can give you a general replacement guide.
There is a piece of equipment that gives poundage readings when the spring is compressed. Some members have one and it’s interesting to see what the difference is between a new spring and an old one.

Saying all of the above, the valve springs are made to exceed the onset of valve bounce at maximum revs when new and even when they are 1,000’s of Km’s into hard use, they still would minimise valve bounce for normal road use.

Take the latest Jap bikes for instance. Many rev to 14,000 and above and springs close the valves.
These valves are small though, stems are thin and the overall mass is far less than a 1960’s machines valves.

For those who are not quite sure what valve bounce is, it’s fairly simple. The valve on all but the desmo bikes need a spring to close the valve. If the spring is too weak, the valve train will not follow the heel of the cam exactly as engine speed gets close to maximum.
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Defective springs (and valve float) are all things of the past. Get with the 1990s...

I would lose that mechanic that says the spring is "too stong"... sheesh...

What undoubtedly happened is that there was some problem with the follower / cam that caused the metal to wear away. The mechanic replaced the follower, but the cam was already buggered, which wasted the new follower.

What will happen now is the mechanic will replace the follower and spring, and in three weeks you'll be in the same place...

 

This was the service center at the volvo dealership I purchased the suv at. I usually have a local mechanic that I love, but the car is still under warranty.

 

Oh man...

I guess Volvo dealers can hire high school dropouts too...

Try and get your mech to come along and look at the cams when the cover is off. The problem should be visible.

 

We all need to replace valve springs on an ongoing basis if we want best performance.
Failing to replace springs when it becomes necessary can allow valve bounce to occur before maximum revs are reached, and in extreme conditions, big damage.

So when should you replace valve springs?
All workshop manuals give measurements of new springs, easy to do a comparison whilst the head/s is/are off and everything is stripped. Keeping a record of kilometres travelled to measurements taken from new can give you a general replacement guide.
There is a piece of equipment that gives poundage readings when the spring is compressed. Some members have one and it’s interesting to see what the difference is between a new spring and an old one.

Saying all of the above, the valve springs are made to exceed the onset of valve bounce at maximum revs when new and even when they are 1,000’s of Km’s into hard use, they still would minimise valve bounce for normal road use.

Take the latest Jap bikes for instance. Many rev to 14,000 and above and springs close the valves.
These valves are small though, stems are thin and the overall mass is far less than a 1960’s machines valves.
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The spring is extremely stressed at this bind point and you should ensure that you do not approach this bind point otherwise the cam lobes, lifters and follows will be damaged.