Abnormal Engine Deposits Only On Rear Bank

[The Critic]

Last Saturday, I went with aznboi24 to have the 105,000-mile service performed on his 2001 Acura CL Type-S. This service included the replacement of the timing belt, water pump, both timing belt tensioners, idlers, camshaft seals, both drive belts, upper/lower radiator hoses and the spark plugs. In addition, the valves were adjusted as part of the service since the engine was emitting a diesel-like clatter.

When the valve covers were removed, the front bank was very clean. However, the rear bank showed an abnormal amount of deposits.

Please excuse the poor quality of the pictures as they were taken with my phone.

Here are some pictures of the front bank:

Now, here are some pictures of the rear bank:

While removing the valve covers, the technician noticed the PCV valve was not working properly. I personally shook the PCV valve and did not hear a rattle, so it is likely the valve had failed. It is quite possible that the failed PCV valve caused the abnormal amount of deposits on the rear bank.

After flushing the PCV valve with carburetor cleaner, it began to rattle normally. Still, we went ahead and replaced the PCV valve with an aftermarket replacement from AutoZone.

As for the oil change intervals, the car was purchased used with about 75k. For the last 30k, it has seen 7-10k intervals with Mobil 1 and Valvoline Synpower and premium filters.

So, enjoy the pictures, and let me know what you folks think!

 

[killagt]

Look normal to me, im sorry wat I try to say is, its look clean.

 

[JHZR2]

I think the explanation may be heat load. The front bank is in the way of more airflow, and has a higher chance to shed heat. Also, unless the piping is exactly equal, being fuurther from the radiator, there may be slightly preferential flow to the front cylinders due to lowr pressure drop, again, causing a slight rise in temperature.

Remember, oil oxidation can double in rate with just a 10C rise in temperature, that delta is easy.

Bad PCV doesnt help, but on the only "V" engine we own, the PCV only vents from one head, not the other. Not sure how it works with that engine, or how it matters - it either vents everywhere or nothing perhaps, and does it all ether well or poorly.

While definitely darker and slightly more varnished, if that was the onl thing, Id not be concerned. Were the valves on the rear bank tighter than those on the front?

One interesting thing to observe would be compression and leakdown on front vs. rear.

 

[Gary Allan]

I'd say one looks normal ..and the other looks brand new. The difference could be due to anything from PCV routing to the rear bank just getting heat soaked more ..both..

 

[hominid7]

At 105,000 miles i'd say that this engine has been well cared for.

Nice photos!

 

[aznboi24]

Also I did seafoam treatment for the intake for the first time on the engine at 100k and at 105k. The treatment did reach all 6 cylinder though. Not sure if that made the problem worse or caused the discoloring all together. Honestly I was quite concerned to see the difference.

Thanks to The Critic for posting this.

Originally Posted By: hominid7
At 105,000 miles i'd say that this engine has been well cared for.


Thanks! I've only had the car for 30k miles and I do baby it a lot. For as much as I love the car, I take real good care of it as shown in the extensive 105K service.

 

[The Critic]

I should also add this bit of information: the PCV vents from the rear valve cover on this particular engine.

Originally Posted By: Gary Allan
I'd say one looks normal ..and the other looks brand new. The difference could be due to anything from PCV routing to the rear bank just getting heat soaked more ..both..

I'm sure a lot of people remember me by my poor maintenance practices on the Saturn, but my valvetrain more closely resembled the front bank despite 95k of extended drains on conventional oil.

 

[Gary Allan]

Quote:
I should also add this bit of information: the PCV vents from the rear valve cover on this particular engine.


Reverse them. Now before you pull some "but there's no baffling in the rear one" ..see if the valve covers are identical otherwise.

 

[Virtuoso]

I would not worry one bit. Looks great!

 

[zulu]

Nice Comptech headers! (pic #1) +1 for the rear bank running hotter than the front.

 

[ADFD1]

Looks pretty good to me for the miles on the engine. I've seen MMO clean that junk up in one OCI. Truth is I don't think I'd lose much sleep over it. As a few guys mentioned probably related to heat.

 

[Propflux01]

Or the front bank has been replaced before?

 

[buster]

Looks clean. May have been cleaner if the PCV valve was replaced sooner.

 

[PT1]

Looks fine to me. Run some PP in that engine.

 

[Gary Allan]

Originally Posted By: PT1
Looks fine to me. Run some PP in that engine.


Yeah, but you'll never see a difference. Both will have 46% less of whatever is on them. The new head will look like polished aluminum ..maybe with a media blast treatment ..and the dark one will just look ..new. Same distinction.

Why bother with PP?

 

[PT1]

Originally Posted By: Gary Allan
Originally Posted By: PT1
Looks fine to me. Run some PP in that engine.


Yeah, but you'll never see a difference. Both will have 46% less of whatever is on them. The new head will look like polished aluminum ..maybe with a media blast treatment ..and the dark one will just look ..new. Same distinction.

Why bother with PP?

PP cleaned that brown varnish looking stain off my kids CRV in about 20,000 miles.

 

[Gary Allan]

[sarcasm]....[/sarcasm]

 

[PT1]

Originally Posted By: Gary Allan
[sarcasm]....[/sarcasm]

HOW DARe YOU QUESTION THE CLEANING POWER OF PP....HARUMPH!!!

 

[jstutz]

Originally Posted By: PT1
Originally Posted By: Gary Allan
[sarcasm]....[/sarcasm]

HOW DARe YOU QUESTION THE CLEANING POWER OF PP....HARUMPH!!!

Did you forget that pennzoil causes sludge... Just kidding but threw that in there becuase i just read someone saying that on another forum. Will this sludge rumor every go away?

 

[mechtech2]

I have a dial up, and those massive pictures are still loading.
But more varnish or sludge in one bank indicates more heat, or poor PCV flow, or both. Possibly bad drainback, but this doesn't seem likely here.