L18 burning oil + comp. test + rebuild

[Genaro]

Hi guys,

My truck has been burning oil the last year, i didnt bother about it because it was running strong, but in the last weeks it started wetting the cyl 4 and 2 spark plugs with oil and therefore start in 3 cyl one out of three of four times... 

Blue-ish smoke comes out the pipe during acceleration...and kinda grey at idle (very little)... 

I've changed valve stems seals and adjusted valves last week but it didnt change, valve side to side movement is almost inexistent... Im using 20w-50 mineral oil (its summer down here in SouthAmerica) 

Oil pressure with cold engine is 50-55 psi and drops to 30-40 when hot...

Refrigerant level is the same since always...no oil traces in there neither foam in the oil cap. 

I just did a compression test following a post that i found here with cold engine & dry/wet cylinders and the results are down here

Should i re-do the test with the engine hot? 

What would be the next diagnose to perform before removing the head ? 

 

(Sorry for my english if there is something that its not properly explained/written)

Edited April 6, 2019 by Genaro
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[DanielC]

By refrigerant, I think you mean coolant, the radiator, engine cooling.

Refrigerant, at least in USA English, is used in air conditioning.

 

My opinion, the compression is a little low.  It may be time to rebuild, or get another engine. 

Here in the USA, I can usually wait for a useble engine to show up in a junk yard.

 

You know Argentina's options for auto repair much more than I do.

[datzenmike]

I think 150 is reasonable and while 170 or higher would be nice, there's still lots of miles left in it. Compression numbers would be even higher on a warm engine. The best thing of all is that all cylinders are within 10 PSI of each other... however burning oil is troubling.

 

30-40 oil pressure when warmed up is a bit too low. I would say that the rod bearings and probably worn out. Worn bearings will have more clearance and more oil will bleed out from between them and the crankshaft. This oil will be flung outward and some is bound to splash all over the cylinders and could easily over load the oil rings. If you are thinking of rebuilding you would want to replace the mains and the rod bearings anyway, so you have nothing to loose replacing them now. The only extra cost is the oil pan gasket.  Yes you can replace the main bearings by sliding them around the crank till at the bottom and removing then. New ones are the reverse of removal. The brace between the torsion rods can be unbolted and removed in order to remove the oil pan to get at them. If this doesn't help the bearing are already done and waiting. 

[Genaro]

Thanks for the replies, guys!

Im warming up the engine right now and will do the test again.

 

Engine haves 57k miles since brand new, the previous owner told me that the first owner kept the truck sitting stored for 10 years, now that i started using it daily, this problem came up...

Maybe some rust build up in the cylinders during that time and is agravating with the use... 

 

I've never found metallic particles when doing an oil change...but i know it doesnt mean a lot. 

 

I will update after the compression test with hot engine...

 

Damn! I dont want to crack the engine open... 😕😕😕

[Genaro]

 

Okey, looks like Postimage doesnt want to upload the pic...

Hot engine compression readings...

Cyl 1 - 175 psi

Cyl 2 - 165 

Cyl 3 - 170

Cyl 4 - 175  

All dry... After adding oil, only cyl 4 went from 175 to 180 psi...the rest showed the same values... 

Thanks for the feedback! 

Edited March 18, 2019 by Genaro

[Genaro]

Exhaust blows and sucks the paper...bad valve seats? But then how compression shows acceptable values... 

Maybe i've adjusted valves lash wrong? 

Excuse if these are stupid questions...im lost!

[datzenmike]

Stupid... is not asking questions and you English is excellent..

 

40 is the warmed up oil pressure?????

6 hours ago, Genaro said:

Damn! I dont want to crack the engine open... 😕😕😕

 

Removing the oil pan isn't really 'cracking it open' any more than taking the valve cover off. Replace the main bearings and the rod bearings and try to get your hot oil pressure up to 55 when driving around.  

 

What brand of oil are you using? I ask because today's oils are slowly phasing out the zinc anti scuff additives that our engines (made 40-50 years ago) need. I recommend a light diesel oil like 15w40 Shell Rotella T4 or Chevron Delo 400. They are still high in ZDDP levels.

[Genaro]

12 minutes ago, datzenmike said:

Stupid... is not asking questions and you English is excellent..

 

40 is the warmed up oil pressure?????

 

Removing the oil pan isn't really 'cracking it open' any more than taking the valve cover off. Replace the main bearings and the rod bearings and try to get your hot oil pressure up to 55 when driving around.  

 

What brand of oil are you using? I ask because today's oils are slowly phasing out the zinc anti scuff additives that our engines (made 40-50 years ago) need. I recommend a light diesel oil like 15w40 Shell Rotella T4 or Chevron Delo 400. They are still high in ZDDP levels.

 

Thank you Mike!

 

Today after being running for 20 minutes it was showing 45 psi at idling and around 60 at mid throttle (i dont have a tachometer)

 

You are correct about the "cracking it open" thing... Its just that i cant believe that i will have to start changing bearings on a motor that have so low mileage, but...it is what it is, i was hoping that it could be the valve seals only...

 

The 20W50 oil that im using is from an argentinian brand im not sure about its composition... It says under norms: 

ACEA (Europe) A3/B4

API (USA).         SN/CF

 

i will buy the Rotella one, i've seen it for sale here...

 

Thanks again and appreciate any input..! 

[Genaro]

7 hours ago, DanielC said:

By refrigerant, I think you mean coolant

 

You know Argentina's options for auto repair much more than I do.

 

Yes, i meant coolant ! 

Thanks for the correction...

 

And about parts down here is pretty difficult to get them, very few vehicles with this engine were imported...mostly Datsun cars and Nissan Bluebirds... 

 

Regards!

[datzenmike]

45 at idle and 60 mid throttle is perfect. Not to worry about the bearings.

 

Any chance that it's over filled? Should be just over 4 liters with a new filter.

[Draker]

You'll want to get a good leakdown gauge and check how much air is getting past the rings. Compression numbers do look good, so maybe the issue is not rings. I think a leakdown will be able to tell you a lot more about engine health.

[Genaro]

1 hour ago, datzenmike said:

45 at idle and 60 mid throttle is perfect. Not to worry about the bearings.

 

Any chance that it's over filled? Should be just over 4 liters with a new filter.

 

It has never been overfilled because it burns the oil very quickly...😀😀😀

I change the oil & the filter every 5k miles, but soon later i have to add more....about 1qt after 1-1.5k miles... 

[Genaro]

40 minutes ago, Draker said:

You'll want to get a good leakdown gauge and check how much air is getting past the rings. Compression numbers do look good, so maybe the issue is not rings. I think a leakdown will be able to tell you a lot more about engine health.

Thanks! 

I will research what that leakdown gauge is and try to procure one....

[Loryde520]

I had the exact same problem on my L20B a few years ago. It turned out to be bad rings. I did the job without pulling the motor out. pull the pan and head and it's easy from there on. I rolled in a new set of bearings while I was in there too. It runs awesome now and doesn't use a drop of oil. I was running Delo 400 but have switched to Rotella 15/40.

I hope this helps you out. Good Luck!

[bottomwatcher]

Adding oil and not getting much of an increase in compression should eliminate bad rings from the equation. The rest of the numbers look good. Are you putting the spark plugs back in the same hole. One plug fouling I would check for weak spark. The blue smoke unless it continues for over 30 seconds personally I wouldn't be too concerned about, but if it is more blackish than blue that may be from your misfire. Old engines burn more oil, Its cheap, check your dipstick every other fill up and enjoy your truck.

[datzenmike]

Oil can only get into the engine in two ways... past the oil control rings or the valve seals. You've replaced the seals so for now that only leaves the oil rings. As to the rings, either they are worn out, stuck or plugged with deposits (which would not hurt the compression readings) or they are receiving too much oil for them to handle. (over filled or too much cast off from the bearings)

 

17 hours ago, Genaro said:

 

Engine haves 57k miles since brand new, the previous owner told me that the first owner kept the truck sitting stored for 10 years, now that i started using it daily, this problem came up...

 

 

57K miles or Km? Either way this is very low for a truck that's almost 40 years old even if it sat for 10 years. I always wonder why owners let a good running truck sit and it makes me suspicious. Maybe there was a reason it was parked that you don't know about. I've known people that get an old car and it runs well at first but when you start doing oil changes it cleans out what was keeping it from burning oil. 

 

Have a look for the engine tag. It's on the right side (passenger?) inner fender below the hood hinge. It will list the engine used in it. We got the L20B engine in 1980... maybe this isn't the original engine?

 

 

[DanielC]

I would look at the engine block, just below the number 3/4spark plugs.  stamped is the engine type, L-16, L-18, or L-20-B, then the serial number.

If the PCV valve is missing, or the wrong one, that may allow some oil to get in to the intake manifold.

 

[Genaro]

3 hours ago, datzenmike said:

Oil can only get into the engine in two ways... past the oil control rings or the valve seals. You've replaced the seals so for now that only leaves the oil rings. As to the rings, either they are worn out, stuck or plugged with deposits (which would not hurt the compression readings) or they are receiving too much oil for them to handle. (over filled or too much cast off from the bearings)

 

 

57K miles or Km? Either way this is very low for a truck that's almost 40 years old even if it sat for 10 years. I always wonder why owners let a good running truck sit and it makes me suspicious. Maybe there was a reason it was parked that you don't know about. I've known people that get an old car and it runs well at first but when you start doing oil changes it cleans out what was keeping it from burning oil. 

 

Have a look for the engine tag. It's on the right side (passenger?) inner fender below the hood hinge. It will list the engine used in it. We got the L20B engine in 1980... maybe this isn't the original engine?

 

 

 

Hi, 

Engine is the original one, it would show up in the title if the engine was swapped...here it requires some paperwork and certificates to change an engine on a vehicle.

What i was told was that the first owner was an old man and use the truck on Sundays (typical story), the he got too old/disabled to drive and kept it stored for 10 years, then the 2nd owner bought it and used it for a while and kept in his factory as a second delivery vehicle. 

Everything that i opened was from factory...brake shoes, brake cylinders, clutch cylinders, wheel bearings, steering parts, etc... 

 

I think you guys pointed me in the right direction...must be the oil rings. 

I will buy the parts and start disassembling...i dont decide yet if im gonna to remove the whole thing or do it while installed in the truck... I dont want to suffer from lower back pain ! 

 

Thank you all for all the info, will keep the thread updated as i go further on this..

[Genaro]

[Genaro]

3 minutes ago, DanielC said:

I would look at the engine block, just below the number 3/4spark plugs.  stamped is the engine type, L-16, L-18, or L-20-B, then the serial number.

If the PCV valve is missing, or the wrong one, that may allow some oil to get in to the intake manifold.

 

 

It doesnt have a PCV valve , only a hose from the valve cover to the air filter...but it doesnt wet the filter nor the admission with oil...

Thanks! 

[banzai510(hainz)]

I had a motor that was a oil burner with 50K miles.

MAYBE   Who ever built the motor didn't gap the rings. Each cylinder had a score mark when the ring end binded.

 

how much oil does it use in a week? 1 quart a month? Iwould not worry about it. It kills the misquitos!!!

 

 

If not PVC make sure the crank case is vented. But one should have a PVC valve if stock carb and intake manifold set up.  if plugged that's bad

[Genaro]

Just now, banzai510(hainz) said:

I had a motor that was a oil burner with 50K miles.

MAYBE   Who ever built the motor didn't gap the rings. Each cylinder had a score mark when the ring end binded.

 

how much oil does it use in a week? 1 quart a month? Iwould not worry about it. It kills the misquitos!!!

 

 

If not PVC make sure the crank case is vented. But one should have a PVC valve if stock carb and intake manifold set up.  if plugged that's bad

 

Thanks for your feedback!

It was using 1qt every 1-1.5k miles, and i didnt bother about it, but it started wetting the cyl N4 spark plug with oil and ran in 3 cylinders... So i decided to stop using it until i solve the issue.

 

I will verify if the hose is not plugged, carb and manifold are original from the truck...but maybe that PCV valve was removed by one of the previous owners...🤔🤔🤔

 

 

[banzai510(hainz)]

What I would do is drive this and find another motor or lower block(L16 is exact bolt in ,same chain ect flywhells bolts ect...) and have that motor rebuilt and when your ready to a swap in a day.

 

My 510 the sparkplugs leak oil also. I just don't worry about it right now the motor is still strong.

 

Just make sure the valves are adjusted. If you have a sand blaster I would save the old plugs and try to still use them.  If fouling out plugs fast then you have a real proplem.Some people say don't do this. I used to do it and seemed OK.

 

Just a thought my friend had a old Volvo P1800 and it smoked a lot. Find out the power brake diapram was sucking the brake fluid and we thought the head gasket was bad But you would notice the brake fluid going down.

[Genaro]

1 hour ago, banzai510(hainz) said:

What I would do is drive this and find another motor or lower block(L16 is exact bolt in ,same chain ect flywhells bolts ect...) and have that motor rebuilt and when your ready to a swap in a day.

 

My 510 the sparkplugs leak oil also. I just don't worry about it right now the motor is still strong.

 

Just make sure the valves are adjusted. If you have a sand blaster I would save the old plugs and try to still use them.  If fouling out plugs fast then you have a real proplem.Some people say don't do this. I used to do it and seemed OK.

 

Just a thought my friend had a old Volvo P1800 and it smoked a lot. Find out the power brake diapram was sucking the brake fluid and we thought the head gasket was bad But you would notice the brake fluid going down.

 

Thanks! 

There is very scarce parts available for these engines where i live... forget about finding a whole engine or block...

This video is from an hour ago, after being warmed up and valves lash re-adjusted at .25 & .30 mm with the engine hot. 

 

 

 

[datzenmike]

The left side of the block should have a vent like this...