96 Volvo 850 Engine rattle - Thoughts to cause?

[scot850]

Hi Guys,

Went to meet a fellow Volvo owner and MVS'r today to see if I had any wisdom to add to a dying engine diagnosed by a mechanic.

Story goes, 96 859 10V has close to 300,000 miles on it. Owner works from home now so car stood for a while and when he went to use it this noise started:



Strange part and what makes me question that the engine is bad is that the engine starts of really quiet, and then this noise starts up which sounds like there is something rattling around in the engine. Car has had regular oil changes and run on Premium gas.

Engine runs really smooth otherwise. I thought at first a rod knock, but again would expect some rough running. Also noise comes and goes which is weird.

It almost sounds like there is something loose inside either the cam area or in a cylinder. If it is in a cylinder then it might be a piece of a valve, but being a 10V I would expect rough running again. Hard to pin-point the exact area, but it seems to be in the area of Cyl #1-2.

I am ok going back to do further checks before condemning the car to scrap.

Neil.

[BlackBart]

I would vote bottom end knock. I wouldn't think a sloppy rod or crank bearing would affect the combustion process.

[wizechatmgr]

Check oil quality and quantity, check oil filter to see if it had inhaled some metal filings. To me it sounds like a bearing that's intermittently getting oil, but that's just me. Could have spun a bearing on the crankshaft, but I haven't actually heard an engine when that's happening so I cannot say from experience.

Also pull timing belt cover off. Look there while it's running. But you're right, that sounds rather bad.

[scot850]

Oil was clean, up to level and changed not all that long ago. No floating silver bits in it on the dipstick.

Still can't figure why it was fine when laid up and then this suddenly starts. I can understand the lifters (hydraulic on a 96 if I recall correctly) can get noisy when sitting for a while, but they generally don't get this noisy unless they have seized. The bit that still gets me is the engine still ran smoothly and no faltering, just the rattling. I've heard both main and small end knocking and they did not sound like this. The suggestion of a frozen or spun bearing is possible.

I had thought about pulling the plugs and looking down the bores with a camera to see if there was anything loose in the combustion chambers, but again, as these are interference engines I would not have expected it to run, even roughly. It is really weird.

Neil.

[abscate]

Ouch, that’s ugly. Broken camshaft or almost loose rod? Smooth idle points to rod…..

[454cid]

Timing belt tensioner loose, but belt still in place for the moment?

Maybe poke around with a mechanics stethoscope?

[scot850]

As a 96 this will have the hydraulic tensioner. The noise was rom the top of the engine with a stethoscope. Seemed to be more in the Cylinder #1-2 area.

Owner has decided to put the car up for sale stating possible rod knock. I could go to have another look but we are forecast for 4 days of rain and he has no garage accessible as he does not want to move the car and it is parked on the street.

If the timing belt tensioner was loose, the timing would be moving and the engine would not run as smoothly I would have thought? Anything is possible. I'm thinking abscates thoughts on the camshaft or something in that area breaking off could be the issue or a bad/burnt valve. With the oil filler cap off, it does sound bad. The other thing I noticed, come to think of it, is the cam looked quite dry. Maybe no or little oil pressure to the head? Question is, how far do you go pulling it apart to try to find the issue?

Neil.

[454cid]

Really sounds like a parts car or engine swap candidate to me. Drop a v8 out of an xc90 into it?

[scot850]

Have been talking to the owner. I think this is worthy of a 2nd more detailed look , weather supporting I hope! Plan to head down next week wit tools to remove the serp belt as the owner mentioned a noise from last year and was unsure about the serp belt tensioner. Still think this is not the issue, but for my own peace of mind want to make sure. I did not notice the belt jumping or the tensioner moving much, unlike when I had one fail it literally was flailing around. This will also eliminate any of the other items that rotate on the belt path like the alternator, the A/C compressor and the PS pump. It will also allow access to remove the TB cover and check the hydraulic tensioner and the belt not having jumped possibly.

I will also take my boroscope and check the bores for anything broken like a valve.

Neil.

[scot850]

Well am I embarrassed! I listened to what a mechanic had told the owner and that the engine was toast. Glad that you guys all chipped in and strongly suggested I go back for a second look. Something did not sit right in my pea sized brain that the noises did not fit the crime.

So did the suggested pulling of the serp belt and forgot you have to pull the tensioner to get the cover off the timing belt. Wanted to minimise starts so wanted to be able to check the ancillaries being removed from the equation and noise making were not the issue and be able to get better access to the area with my stethoscope to try to pinpoint the noise location and also check the timing belt to make sure the hydraulic tensioner had not failed or timing belt jumped.

By shear luck (would never happen on my cars........! ) the timing marks were almost on the alignment marks. Belt was spot on.

Got to use my new jump pack as the owner said the battery was low. Worked great. Got him to start the engine and and got my stethoscope onto the head near cylinder one and the cam shaft. I could hear the knocking but not from the top. Looked down and saw the water pump pulley wheel dancing all over the place!! The pump bearing had failed but not badly enough yet to seized and toast the engine!!

Switched the engine off immediately and we were both delighted. Now the worrying part is that although the timing belt was 'professionally' changed in 2016, the car has only done about 50,000km (40k miles) since. So either the mechanic used crap parts or the pump was not replaced.

Now we just have to figure out how to fix it. Good news is he has AMA (AAA/CAA) membership. So hopefully the tow to a repair shop should be free. Also as I have already removed the serp belt tensioner and timing cover, the work is not huge. Trying to decide if I want to step up and do it for Ed. He is a recent graduate and intern so I would assume money is not growing on trees. Also ideal opportunity to use the hoist and not have to lay on my back cursing trying to work on the water pump. I can now do all that while standing!!

Ed was offered $6-650 for scrap for his car which is also amazing! Hopefully we can now pull this back from the edge!!

Thanks guys for your encouragement and advice.

Neil.