2004 S60 B5244S6 uniformly low cylinder compression

[ttrikalin]

Hello all,
I would really appreciate your thoughts on how I should proceed with my car. Any pointers, thoughts and suggestions in general are most welcome...

I have a NA 2004 FWD S60 (B5244S6) with 145K [miles] on the factory engine.

Symptoms: The car has been consuming some oil (~1 quart [1 liter] per 2K) over the last 40-50K at least.

Exam: I did a compression test (throttle full open, measured twice, over two weekends). Numbers are in PSI, dry and wet (10 cc of motor oil):

#1: 117.5, 155
#2: 125, 157.5
#3: 122.5, 150
#4: 120, 162.5
#5: 125, 160

My gage shows increments of 5 PSI, so I interpolate/average over 2 reads in the numbers above. I realize I am being spuriously precise.
Based on the alldatadiy site, the specs should be 190-210 psi, so these numbers are low -- at least uniformly low.

History:
1. I got the car with 30K on it, and I do not know its prior history. I am to blame for the last 110K miles, and I have run it low on oil once or twice, as inferred by a brief flash of the oil sensor light at a hard turn.
2. It probably needs a PCV job: The dipstick tube and the oil cap orifice are smoking with the engine running. A glove over the oilcan tends to inflate (slightly). For what it's worth, the glove test indicated a slight vacuum 10K ago.
3. I started maintaining the car myself at 70K, after realizing that I was neglecting stuff because it was inconvenient to bring it to the shop (I have a great shop near home -- the car talk guys' shop actually) but it just is not convenient and I was letting maintenance slip.

Questions:

1. Am I correct in interpreting the difference between the wet and dry as an indication for worn rings (at best). I understand that I still have not checked the valves.
2. I do not have a compressor and cannot do a leak down test at home. It is acceptable to blow air in the cylinder from the spare to simple try to hear from where the air escapes -- or should I just drive it to the shop?
3. How urgent is the PCV job? Can it wait until I find time to pull the engine off for a rebuild?

Thanks for considering,

tom

[oragex]

The compression is fine, it's when one cylinder is much lower than others that you have an issue

The oil consumption is due to the clogged pcv valve. Replace the breather, the pipes, remove the oil pan, clean the pcv oil passage inside, remove sludge if any, clean the suction pipe mesh, check the o-ring seals inside (better replace them). About a $700 job + parts at a smaller garage

About how urgent the job is, nobody can exactly tell, if you only keep the car for another 10k miles it can be ok, but at any time the pressure built up will damage some of the engine seals => more $.

[jimmy57]

PZEV engines from most makers use a little oil. 1 qt/2000 miles is a little oil.
The PZEV versions use low tension rings and that has proven to allow more oil consumption and replacing the rings might not drop the consumption enough for your expense. The engines run cleaner and the combustion byproducts getting into oil are reduced so you don't have that to offset the slight use of oil.

Did you check compression immediately after starting with a fully warmed up engine? Did you prop open throttle while obtaining those numbers?

[ttrikalin]

Thanks to both, really

oragex, I understand the point about urgency -- I will do the PCV in the next 3-4 weekends. I will remember to take photos/videos.

Jimmy57, indeed I did the test with full throttle and the engine in normal operating temperature.
FWIW, whether with full throttle or not depressed throttle, the reading is the same after 8-10 cranks.

However, the compression numbers are well outside the range and change a lot by 30-40 PSI after the addition of oil... I did not find any mention of alternative specs for the PZEV engines (keeping looking and will post updates).
Indeed, as oragex said, the uniform numbers suggest even wear or a systematic reason (such as a ... bad gage -- this I have ruled out; or perhaps low tension rings, as was mentioned by jimmy57).

Thanks for the replies... and take care

tom in MA

[JRL]

Readings are just fine for its age
Try a Seafoam treatment, you may gain 5 to 10 across the board (or maybe not, but it can't hurt)!

[jimmy57]

I asked only to assure the readings were not low due to the method obtained.
I always instruct to crank until pressure maxes out. The hose rigidity, length of hose, quick connect flow rate, etc can affect how many compression strokes it takes to fill up the hose before you get the max reading. Many instructions on compression testing will list 4 or 5 compression cycles.
That gain does look like bad rings but one more thing does affect the dry vs. wet number: how much oil.

As stated already, clean/replace the crankcase vent system and then monitor. I would advise that depending on how much debris you find in the lower port once the box is removed from block that you may need to drop oil pan and clean the return oil passage. That lower passage goes down below the oil level into sump and if it is clogged the condensed oil can't drain and it will use more oil.

[draser]

It sounds like worn rings. Not sure what the lower limit is for non-turbo, but I'm thinking in the 150 range. Rebuilding PCV does improve breathing, nothing else. I'd try another gauge and repeat test.

[ttrikalin]

Thanks to all.

To summarize, the PCV job has to be done irrespective of the compression results. I ordered the kit from FCP and I will do it this weekend. I will try to document the whole thing for posterity. I may have to drop the oil pan for thorough cleaning, so I will budget time.

The compression numbers (120-125 PSI dry; 150-160 wet w/ 10 cc oil) are low according to specs (190-210 PSI), the largish gain in the wet test suggests worn rings.

At some point I will tackle the rings, but not before the winter break. Too much going on till then at work.

thanks,

tom

[vtl]

What oil do you use? 2002 V70 w/ B5244S and 136k miles on the odo was consuming some 5w30 oil. Not much, but I've switched it to 5w40 (Amsoil synth). Changing oil every ~10 months, level does not drop even two X's on the dipstick. Engine is also quieter on a thicker oil.

[ttrikalin]

I use 5w30, which is what the engine requires.
I understand that the heavier oil may be consumed less, but I am not clear on whether this is a good thing or not.

A penny for your thoughts.

Here's a summary of mine: Oil consumption is a manifestation of an underlying problem. Fixing oil consumption by means of heavier oil use does not fix its cause; it might just rob you of your only way to gage whether the underlying problem has worsened (the oil consumption rate would grow...).

Happy to hear more about this, I have not read stuff about oils and my rationale may be naive.

take care,

tom in MA