Do failing failed turbos oil plugs?

[Bellow]

As per thread title. The engine in my car with 'Engineered by Mercedes-Benz' emblazoned upon it has been consuming oil at the rate of 0.5-0.7 litres / 500 miles for a while now and the suspicion has been it's gone the way of all smart Suprexes and is allowing it past the rings to burn. At this level of consumption the spark plugs can be expected to be oily and ready to foul and the advice is to rebuild the engine ASAP.

Except that when I pulled the top three plugs today they are as clean as can be - absolutely no carbonisation or oiling.
There is some oil in the intercooler but some carryover is expected. When a turbo is failing and the oil consumption rising as a consequence, can it reach this level of consumption (bear in mind it is only a 700cc engine) without it showing on the plugs?

Apart from the oil consumption, it's running well and the only other sign is oil spots on the rear panel after a 100ish mile blatt which I expect to stop now I've replaced a weeping throttle-body seal (not the cause of the high oil consumption as I damaged it investigating the high oil consumption). Could the oil spots be a clue to something else? There are no signs of leaks (other than the aforementioned weeping) so I can only assume TB seal was the cause. No engine light to indicate cat malfunction, but smarts can be using considerable amounts of oil and the cat cope.

Any ideas? More investigation of the turbo required? Car has done 60,000 miles and all but the first 4000 are by me.

 

[Dieselman]

Unburnt oil in the exhaust points towards turbo exhaust side bearings going.

 

[Bellow]

Unburnt oil in the exhaust points towards turbo exhaust side bearings going.

Can the oil get past the cat in that scenario to form the oil spots on the bodywork? Or is that more likely the weeping seal (now fixed)?

 

[Dieselman]

I would think it can get past the Cat before it is fully hot or if there is enough oil.

If the oil was being ingested pre-combustion there would be blue smoke as it was burnt.

 

[Bellow]

I would think it can get past the Cat before it is fully hot or if there is enough oil.

The spots appear on a longish (up to temp) run. Suspect the weeping seal the culprit. I'll know next time out.

If the oil was being ingested pre-combustion there would be blue smoke as it was burnt.

Not with smarts. Even when they are burning it after the rings have failed, they go a long way before blue smoke appears. Cat suffers though.

Failing turbo with oil exiting on exhaust side is next on the list to check I think.

 

[ccp]

My smartie (600cc) wasn't using that much oil but it was using about 0.5l in 1000miles. I replaced the PCV valve and associated plumbing and the oil consumption dropped to about 0.5l in 3000 miles. There was no blue smoke in evidence before hand or symptoms other than a very "oily wet" PCV. I was a bit suprised at the effect of changing it!

Did you check the compression when you had the plugs out?

 

[Ian Donkin]

If this is a 450 with the 699cc engine, I believe they are prone to burnt out exhaust valves around the mileage you are suggesting... I know a couple of smart specialists who spend their lives rebuilding these engines so I don't believe it's the end of the world.

 

[Bellow]

My smartie (600cc) wasn't using that much oil but it was using about 0.5l in 1000miles. I replaced the PCV valve and associated plumbing and the oil consumption dropped to about 0.5l in 3000 miles. There was no blue smoke in evidence before hand or symptoms other than a very "oily wet" PCV. I was a bit suprised at the effect of changing it!

Did you check the compression when you had the plugs out?

The PCV valve was replaced a short time back - it was goosed.
Didn't have a compression tester so couldn't, but the plugs are too clean for their to be oil passing through the chamber.

If this is a 450 with the 699cc engine, I believe they are prone to burnt out exhaust valves around the mileage you are suggesting... I know a couple of smart specialists who spend their lives rebuilding these engines so I don't believe it's the end of the world.

It is a 450 with the 700 engine. The exhaust valve failures tend to happen after and as a consequence of the oil-past-the-rings issue or other ignition related problems. (Slow burning, retarded timing due to lowered octane, less fueling as oil is detected by Lambda, losing spark on one plug,etc - are all candidates to burn a valve).

I think the reason may be coming apparent though - and it's not a fault with the car. It may be as simple as me allowing it to warm up while parked nose up a hill and the oil not draining from the turbo back to the sump well enough and exiting via the seals. (The turbo is situated very low and I'm running with a 15W/40 - a touch thicker than most use).

 

[Dieselman]

I think the reason may be coming apparent though - and it's not a fault with the car. It may be as simple as me allowing it to warm up while parked nose up a hill and the oil not draining from the turbo back to the sump well enough and exiting via the seals. (The turbo is situated very low and I'm running with a 15W/40 - a touch thicker than most use).

I thought you would have known to not do that. Having said that, if the turbo seals are allowing oil past when cold, they must be getting a bit worn.

 

[Bellow]

I thought you would have known to not do that.

I have never liked driving off with a motor still cold - but it could be time to re-appraise that!

Having said that, if the turbo seals are allowing oil past when cold, they must be getting a bit worn.

At 60,000 miles and a hard worked wee turbo at that, I suppose some wear is possible.

Do you think it's worth checking end play in turbo - or just re-appraise warm up regime and look for the replaced TB seal to have cured the oil spots and see if the oil consumption falls back in line?

 

[Dieselman]

For now give it a flush and change your warm up routine as you won't be doing the engine or turbo any good with the one you have at present.

The rings need pressure to seal, otherwise you will have excessive blow-by and the intake needs pressure to stop oil migrating past the turbo seals. The oil is at ~50psi, intake pressure at zero...

I'm surprised you use a thicker oil as that is likely to increase cold wear and any 40 weight oil will have adequate hot protection.

 

[Bellow]

For now give it a flush and change your warm up routine as you won't be doing the engine or turbo any good with the one you have at present.

The rings need pressure to seal, otherwise you will have excessive blow-by and the intake needs pressure to stop oil migrating past the turbo seals. The oil is at ~50psi, intake pressure at zero...

Both points noted and will be incorporated (except for flush).

I'm surprised you use a thicker oil as that is likely to increase cold wear and any 40 weight oil will have adequate hot protection.

It spends a lot of it's life boosting like crazy on long hills so I chose the 40 for the additional HSSS over the 30 weight. The 'careful' warm up regime was a counter to its additional cold viscosity.
The Suprex turbo has a particularly poor drain path back to the sump I'm told, sits very low on the block, and the hill I've been parked on quite steep.

I'm going to run for a bit with a new warm up regime and see what transpires.
I am mighty relieved it doesn't need the complete rebuild though.

 

[Dieselman]

It spends a lot of it's life boosting like crazy on long hills so I chose the 40 for the additional HSSS over the 30 weight. The 'careful' warm up regime was a counter to its additional cold viscosity.

I agree about 40 weight oil giving greater hot protection, but why not go for a wider cold viscosity?
Even my ol' sludge-burner is on 5W-40.

 

[Bellow]

I agree about 40 weight oil giving greater hot protection, but why not go for a wider cold viscosity?
Even my ol' sludge-burner is on 5W-40.

Two reasons.
One, I'm keen to stick with the products I sell - and the only 30 weight then available was a 10W/30.
Two, a 5W/40 (to use your example) is an oil never thicker than an SAE 5. The gap to SAE 40 is bridged (when hot) by viscosity improvers (VIs) which are long chain polymer molecules, and in time they shear thinning the oil. The wider the gap between the the two numbers the more the VIs are employed. I prefer as stout a base oil as possible (for improved HSSS).
(Incidentally gear trains are the cruelest to VIs - which is why (along with minimised warm up relative to actual running) marine engines tend to run with straight grade oils as they are festooned with myriad gear drives for boat ancillaries. Gears chop up the polymer chains).

 

[Dieselman]

Two reasons.
One, I'm keen to stick with the products I sell - and the only 30 weight then available was a 10W/30.
Two, a 5W/40 (to use your example) is an oil never thicker than an SAE 5. The gap to SAE 40 is bridged (when hot) by viscosity improvers (VIs) which are long chain polymer molecules, and in time they shear thinning the oil. The wider the gap between the the two numbers the more the VIs are employed. I prefer as stout a base oil as possible (for improved HSSS).
(Incidentally gear trains are the cruelest to VIs - which is why (along with minimised warm up relative to actual running) marine engines tend to run with straight grade oils as they are festooned with myriad gear drives for boat ancillaries. Gears chop up the polymer chains).

But can't use EP oils as a result of the other requirements.

I am aware of the VI's used to widen the oil viscosity, but over a normal drain period have never noticed oil thinning, in fact isn't the trend to use thinner oils for extended life operating, to combat the eventual thickening that will take place.

 

[flango]

The worst thing you can do to an engine is let it warm up on idle before driving off that's how most wear occurs.

Drive off cold using the minimum amount of revs between changes until the engine warms up.

Both our Volvo's limit the rpm available until the engine is at temp same with SWMBO sister BMW that actually shows on the rev counter what maximum revs are and it varies by temperature.

 

[markjay]

As above... the only proviso is that you should wait till the oil pressure is up before driving off. Sadly oil pressure gauges have been removed from most modern cars, so the advice is to wait 5-10 seconds until the engine rpm has stabilised and them drive off.

This prevents having the oil diluted by excess petrol in the combustion chamber during cold idle, and helps bring the engine up to optimal working temperature faster.

This does indeed contradict what I was thought as a young driver, i.e. that the engine needs to be 'warmed-up' before driving off.

 

[Bellow]

But can't use EP oils as a result of the other requirements.

Do you mean extreme pressure?
My oil has a good anti-wear additive without having to lean on ZDDPs.

I am aware of the VI's used to widen the oil viscosity, but over a normal drain period have never noticed oil thinning, in fact isn't the trend to use thinner oils for extended life operating, to combat the eventual thickening that will take place.

The move toward thinner oils is all about fuel consumption and CO2 output at the point at which cars are tested for homologation. Oils can thicken in use - but that's them getting dirty. If the VIs are breaking down the new thickness is just dirt.


The jury is out on warming up prior to driving off.
My issue here though is not one of wear but of poor oil drainage when cold - or at least I hope that's all it is....

 

[Tiff]

U R Pinger and I claim my 5 pounds.

 

[Bellow]

U R Pinger and I claim my 5 pounds.

Never denied it and don't recall offering a fiver!

Do I know you from somewhere else? Or were you just Googling?