engine and drivetrain Any Truth To The Following Claim?

[Marshizzle]

I was doing a little looking into changing rings with the motor in the car when I came across this yahoo answers discussion. What do you guys think about this?

 

 

"Are you ready for this.. Rebuilding the bottom end down to rings and pistons is not worth it. Almost all the power loss in these motors is in the head. A way to go about it is get the head off and the cross member off. Remove the pan and oil pump and lower timing cover and just replace the bearings right there in the car, just slide the old main top bearings out by shoving in the new ones just keep it clean. Put a new oil pump and chains and guides in. Maybe a new tensioner and spring. Oh and get some oil pump shims just in case. Really if I didn't mention a part don't replace it that means the gears too. 
Now something that's really going to make you scoff. Before you even crack open the engine. Do an oil change with a new filter and improvise 3/4 of a quart of oil for any ATF. Run it or drive it around till you get the oil light to flicker at idle. Change the oil filter add whats needed of 1/2 oil and 1/2 ATF and repeat and see if you can get the oil light to flicker at idle again. What this is doing is cleaning the oil control rings and the little ring grove drain holes in the pistons. The older rings are extremely long lived and I mean over a million miles kinda thing before enough blow by happens to rob you of power. The smoke an old BMW engine gets especially the 2.0l is almost all in the oil control rings. 
Pistons are huge bucks and you probably won't get as good of a ring seal even again with a hone and ring. The cylinder bores almost always look like new no matter what the miles are and the taper is almost always less than a .001. 
Total cost 1300.00 to 1500. 
Figure 100.00 for the gaskets
100.00 for timing stuff.
400.00 for a head work
500.00 for a good oil pump don't get suckered by low cost pumps get the good stuff. 
200.00 for bearings (get standard) 
The rest for chems and stuff like that.
If you got pistons your looking at last time I looked about 1200.00 them are spendy things."

 

[Rocan]

Some sense in there, but very ill advised. There is no harm in running some seafoam through your oil and motor, and although it is true that sticky oil control rings can cause oil burn, and that the m10 bottom end is quite bullet proof, things DO wear out. Chances are if the main bearings are worn, the piston rings are also worn. Doing all this work and not replacing pistons and rings is just poor craftsmanship, and a bodge job no matter how you put it. Running ATF through an motor of unknown condition is a bad idea... It's good because it loosens up all the crap in the motor, but it is bad, because, well, it loosens up all the crap in the motor and it could get stuck in a worse place then it was before.

 

So in short, you have nothing to lose by replacing the oil and running some seafoam or kerosene or atf (small amounts, very briefly) through the motor and seeing if it improves things. Just make sure you properly flush the engine with fresh oil TWICE after doing something like this. 

[jimk]

1. ATF is not as much a detergent cleaner as "old wives tales" say it is.  It won't clean ou the dino dung from the oil return holes in the pistions.

2. Ring gaps provide the blowby and loss of ring tension (sealing).  These motors started life on oil that wasn't half as good as today's oils, so believing there isn't a lot of ring wear is wishfull thinking.

3. Doubt there will ever be a good pan gasket seal with oil seeping onto the gasket flange while the pan is replaced..  It will drip for a good long time if waiting for it to stop dripping.

4. If it is desired to just flush it, use a fluch product designed for flushing, not some heresay, unsubstantiated method.

 

Edit:  I couldn't resist -- Throw in a set of rods and mains, grind the valves and let her go.  No need to check the rings.

Edited May 20, 2013 by jimk

[Rocan]

i agree with jim on everything except number 2... Old oil was better; new oil is just more high-tech and is processed using far better techniques to make it seem better, but it is thinner and has certain additives that aren't very good for our motors (part of the reason I use 20w-50 that is specified for "diesel" engines). Same deal with old gasoline... You used to be able to get high octane leaded fuel at the pump which makes engines quite happy... too bad it's so bad for the environment. Nowadays everything has ethanol in it, and unless if you built your car from the ground up to burn ethanol, it is simply a worse fuel. If you built your car to run on e85 though... as Jeremy Clarkson would say.... POWAAAHHHH!!!

[jimk]

i agree with jim on everything except number 2... Old oil was better; new oil is just more high-tech and is processed using far better techniques to make it seem better, but it is thinner and has certain additives that aren't very good for our motors (part of the reason I use 20w-50 that is specified for "diesel" engines). Same deal with old gasoline... You used to be able to get high octane leaded fuel at the pump which makes engines quite happy... too bad it's so bad for the environment. Nowadays everything has ethanol in it, and unless if you built your car from the ground up to burn ethanol, it is simply a worse fuel. If you built your car to run on e85 though... as Jeremy Clarkson would say.... POWAAAHHHH!!!

I think a brush up on SAE Viscosity grades is due.  They are the same today as 50 years ago and haven't thinned any.  If you are referring to the shake the bottle test, then you need to brush up on what Viscosity Index is.  Old oil was not better, back then the best there was is API SE, allowed to thicken 400% in the high temp IIIc API test.  Synthetics in those days thickened around 8% in the same test and would be able to pass the test after 3 times the test time.

[Rocan]

I think a brush up on SAE Viscosity grades is due.  They are the same today as 50 years ago and haven't thinned any.  If you are referring to the shake the bottle test, then you need to brush up on what Viscosity Index is.  Old oil was not better, back then the best there was is API SE, allowed to thicken 400% in the high temp IIIc API test.  Synthetics in those days thickened around 8% in the same test and would be able to pass the test after 3 times the test time.

I'm not daft, I know that the viscosity has remained the same. Perhaps my explanation was lacking detail. My main issues with new oils is that they add a ton of additives that are meant to "clean" the engine, or in other words, detergents. Finding non-detergent oils seems a lot harder then it was just 5 years ago and it gets harder every day. Yes, new oils meet much stricter demands, but the push to reduce resistance has gone too far; a lot of new cars are running 0w or 5w oils and are facing premature engine wear (seriously, i've heard of grandmas spinning main bearings on hondas) because of super strict emissions demands. Though that is unrelated. 

[Guest_anonymous]

You will save absolutely neither time nor money refreshing an engine this way. I know I have done it.

[TobyB]

I have never pulled a used piston out of a well- run BMW motor that was worth anything more

than the scrap rate for dirty aluminum.

 

The skirts wear out after probably 50k miles or so, and once they're done, the pistons start

to move around enough that the rings don't seal, the ring lands pound out, and eventually

the rings break, and liberate themeselves through the exhaust valves.  With attendant damage

to the head.

 

I HAVE pulled bearings out of 200k motors that could have been reused.  The crank and bottom end

will last FOR(effing)EVER if you keep enough clean oil down there.  Those bearings put a smallblock

chebby to shame.  Ask engine builders how hard it is to find decent cranks.... they laugh, and ask

'But seriuosly, do you have any decent heads you don't want?'

 

As to oil, I just wish it had more ZDDP in it still, and that people changed it (and their coolant) more often.

 

So yeah, I'd say everything you find on the internet is true, and all you have to do is figure out which truth you

believe in most.

 

Me, after buying good measurement tools, I tend to rebuild bottom ends when they need it.

And if you want great leakdown numbers, buy Total Seal rings. 

 

t

[c.d.iesel]

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