Varnish: Is it really harmless?

[OVERKILL]

One thing I've noticed is that on almost any engine that has had some sort of failure, there is always varnish present. Many will and have argued on this board that varnish is harmless. I'm not so sure about that.

A recent thread on Maxbimmer, where a gentleman's M62 had its timing chain guide shatter had me thinking about this. His engine had some rather significant varnish build-up inside (I'm not posting his pics until he gets back to me and says it is OK) and my theory here is that the varnish causes the hydraulic part of the tensioner to stick, allowing the chain to slap the guide, subsequently breaking it.

There was a thread on M5board last year where somebody had a tensioner fail. Again, significant varnish present.

And of course this brings up many questions with respect to BMW's oil choice, end-user oil choice and the like. There are FAR too many cases of varnished BMW engines to assume that they all were using some sub-par lubricant. This is especially true with M5 owners, most of which use the coveted "TWS".

A quick search of S62 guide replacement yielded these pictures:

That's a Toronto car from what I could tell.

An M62:

This supercharged car is an exception (it is clean) but he is doing the guides because he had the dealership do them (and he paid 6K) and one of the bolts backed out.... No mention as to why they were replaced initially.

Another S62:

Thoughts?

 

[Hokiefyd]

I may be in the minority opinion here, but I'd say that the level of varnish depicted above is not causing timing chain tensioner failures. Or if it is, then the BMW tensioners are much more sensitive to varnish than most. Those engines look very clean to me.

 

[OVERKILL]

Originally Posted By: Hokiefyd
I may be in the minority opinion here, but I'd say that the level of varnish depicted above is not causing timing chain tensioner failures. Or if it is, then the BMW tensioners are much more sensitive to varnish than most. Those engines look very clean to me.


I would classify the level of varnish in engine #1 (the Toronto one) to be at a significant level. The one below it isn't too bad. The bottom one is somewhere in between.

 

[HyundaiGuy]

Maybe BMW is sourcing the guides from the same place Peugeot is getting them for the Mini engines. This is a common repair with Mini. Mine had the chain tensioner and guides done at 28K miles and was part of my decision to get rid of it. Just as in one of the above examples, the bolt started to back out.

 

[Donald]

The problem is the absurd path of the timing chain. Way different than one on my old 289 Mustang.

 

[OVERKILL]

Originally Posted By: Donald
The problem is the absurd path of the timing chain. Way different than one on my old 289 Mustang.


But not all that far off from the path of the Ford Modular engines

Now Ford had guide failures for a few years, but it was because of the quality of the guides. Earlier years didn't have the problem, and neither did later ones.

 

[HerrStig]

Originally Posted By: HyundaiGuy
Maybe BMW is sourcing the guides from the same place Peugeot is getting them for the Mini engines. This is a common repair with Mini. Mine had the chain tensioner and guides done at 28K miles and was part of my decision to get rid of it. Just as in one of the above examples, the bolt started to back out.
A Peugeot engine in the Mini....gulp!

 

[Hokiefyd]

Cadillac's Northstar used three timing chains on each engine; one shorter "jack chain" to an idler shaft near where the camshaft would be in a cam-in-block engine, and then one timing chain that ran to each head. This was done to keep the timing chain runs as short as possible and to avoid what is essentially a 90 degree change in motion. There are VERY few reported failures of the timing chain system on a Northstar engine, despite running long OCIs on conventional ILSAC oil. Maybe there's a correlation there.

 

[KrisZ]

To me the first picture is boarder line sludge.

I think sludge is harmless in majority of cases, however it is a sign that something is happening to the engine that should not. To me varnish means that OCI's for a given oil choice and application were boarder line acceptable.

 

[LeakySeals]

Take a look at any engine pic on here going through a de-sludge/deposit cleanup. Whats underneath the sludge? A heavy layer of varnish. Its no coincidence. Varnish is telling us something about the oil and surface temperatures of the engine. Varnish always mattered, it can glaze cylinder walls, coke rings, make lifters stick. Matters more today. Tighter clearances, smaller oil gallies everywhere. Any sticky buildup in the tiny gallies of the variable valve timing system will cause issues eventually. So while you may be able to live with it, it cannot be ignored as "normal" anymore.

 

[Artem]

Hence why I'm trying so hard to clean up the varnish build up (i'm sure its harmless in my engine though, as it's very light) in my 98 Camry V6.

 

[OVERKILL]

This is also why I made sure the M5 I bought was clean through the fill hole, FWIW

Now, to stir up the hornets nest, most of these engines would have been run on Castrol/BP lubricants

 

[exranger06]

Originally Posted By: Hokiefyd
Cadillac's Northstar used three timing chains on each engine; one shorter "jack chain" to an idler shaft near where the camshaft would be in a cam-in-block engine, and then one timing chain that ran to each head. This was done to keep the timing chain runs as short as possible and to avoid what is essentially a 90 degree change in motion. There are VERY few reported failures of the timing chain system on a Northstar engine, despite running long OCIs on conventional ILSAC oil. Maybe there's a correlation there.

The Ford 4.0 SOHC V6 has a similar design. They were known for failed chain tensioners for the first few years of production. Ford eventually came out with an updated design that fixed the problem.

 

[mechanicx]

Originally Posted By: Hokiefyd
I may be in the minority opinion here, but I'd say that the level of varnish depicted above is not causing timing chain tensioner failures. Or if it is, then the BMW tensioners are much more sensitive to varnish than most. Those engines look very clean to me.


I think so too. Lots or all engines have varying degrees of varnish, but they don't all have early valvetrain failures. Overkill is probably just trying cover for BMW fragility with varnish

.

 

[LeakySeals]

Originally Posted By: OVERKILL
This is also why I made sure the M5 I bought was clean through the fill hole, FWIW

Now, to stir up the hornets nest, most of these engines would have been run on Castrol/BP lubricants

The "C" word. I agree, written about it on here several times. Following high mileage Toyota teardowns/rebuilds for a supposed "oil consumption problem", most of the time all thats found is hardened carbon, hardened varnish in the piston area. Oil used? 90% of the time Castrol something usually GTX or Syntec. I always ask so I'm not just throwing it out there. I think Castrol's flashpoint is too low for modern all aluminum engines.

 

[OVERKILL]

Originally Posted By: mechanicx
Originally Posted By: Hokiefyd
I may be in the minority opinion here, but I'd say that the level of varnish depicted above is not causing timing chain tensioner failures. Or if it is, then the BMW tensioners are much more sensitive to varnish than most. Those engines look very clean to me.


I think so too. Lots or all engines have varying degrees of varnish, but they don't all have early valvetrain failures. Overkill is probably just trying cover for BMW fragility with varnish

.


But that's just it. Many (most?) of the cars will never have this problem. But the ones that DO have the problem, appear to suffer from varnish build-up and I'm curious as to the correlation. This is a huge double roller chain that spans both banks too, so slap and whip may be of far greater detriment in this application than in others.

 

[daman]

Man that's allot of chain,trouble waiting to happen IMO.

 

[OVERKILL]

Originally Posted By: daman
Man that's allot of chain,trouble waiting to happen IMO.


But the Modulars have a lot of chain too, and they are usually problem-free.

 

[daman]

Originally Posted By: OVERKILL
Originally Posted By: daman
Man that's allot of chain,trouble waiting to happen IMO.


But the Modulars have a lot of chain too, and they are usually problem-free.

Im just not used to seeing that much owning only GM non OHC all my life.

 

[HyundaiGuy]

Originally Posted By: OVERKILL
This is also why I made sure the M5 I bought was clean through the fill hole, FWIW

Now, to stir up the hornets nest, most of these engines would have been run on Castrol/BP lubricants

While that is true, I think the problem is the extended OCI as opposed to the oil brand used. Mini recently changed their OCI from 15K/12 months to 10K/12 months due to sludge formation.