Engine Making Oil - Suspected Diesel Contamination

[Rattle]

G'day,

I suspect I have an internal diesel fuel leak which is contaminating the engine oil and overfilling the sump. I drained 12 liters of oil from the engine (expected just under 7 liters). The oil didn't smell too much of diesel, but did appear to be thinner than usual (although both hard to tell).

Questions:

1. Are the fuel pumps known to leak diesel into the timing case (and therefore, sump)?

2. Other than the fuel injector lines, fuel return lines and the fuel pump, is there any other way diesel can get into the sump?

Vehicle:

2006 Hilux, KUN26R, 3.0 D4D (1KD-FTV)

Any advice appreciated.

[dave g]

Has your injectors been done the sets should have been done at the same time when you changed the oil did you have a look at the oil pick up to make sure it was clean

[Rattle]

Has your injectors been done the sets should have been done at the same time when you changed the oil did you have a look at the oil pick up to make sure it was clean

Did you mean injector seals (seats)? Are people pulling the injectors at each oil change interval?

Short answer is no, I have not replaced the injector seats for quite some time - but I don't understand how that would cause diesel to leak into the sump? Is that likely to cause a diesel leak into the sump?

[dave g]

If the injector were taken out the return line may be leaking or cracked that's y Toyota said to all ways use new one's

[Rob_Wood]

Dave, please forgive me, but I don't understand the relationship between possible fuel in sump and injectors. I may have missed something, but I don't recall rattle mentioning injectors.
I'm not completely certain, but if memory serves, then the main way that fuel gets.into the sump would be past the pistons, shot rings. Not that common if the engine has been looked after.

[Gipsy]

Leaking injector or over fuelling is the only way it gets into the sump! No other explanation for fuel in sump oil.
An extra 5 litres of oil sounds more like someone topped up the oil when it wasn't needed. That's a lot of fuel if that's what it is!

I noticed in another post about trouble starting... If you keep turning the engine over without running, the injectors keep pumping fuel into the cylinder without running the engine the fuel has nowhere else to go but into the sump.

[dave g]

Rob in a post dy boxhead55 said he has seen it before I believe he work for Toyota for many years

[Rattle]

Leaking injector or over fuelling is the only way it gets into the sump! No other explanation for fuel in sump oil.

In my experience with common rail diesel engines, there are a few ways diesel will get into the sump:

Fuel return line (loose or cracked inside the valve cover)
Fuel injection lines (loose or cracked at the injector
Fuel pump - leaking through front seal into the timing case
Fuel injectors - leaking through the nozzle into the cylinder

If an injector was leaking that much fuel, I would expect smoke and rough running, which I haven't seen.

The engine oil has not been topped up. It's possible I overfilled the sump at the previous service (I'm actually hoping that this was the case), but i think this is unlikely

I was hoping someone here has experienced one of the first 3, to point me in the right direction.

[ptrl1600]

I would put money on the spill line leaking. The spill/return line is inside the cylinder head cover and is connected to each injector using hollow bolts and a gasket on each injector. While a different engine, my old Nissan ZD30 did the same thing while on a 800km long trip and destroyed the engine. I wasn't aware until I started hearing a knocking sound when slowing down. By the time I was able to get to the next town (Hawker) I drained the oil and filled with 10 litres of the thickest oil I could buy and although it got me home another 400km, I had 13 litres in it when I arrived. The engine was toast! It lost a balance shaft bearing and destroyed the timing gears. A lot of damage caused by a relatively cheap part.

This picture, while a Nissan engine, shows that Numbers 1, 3 & 4 are all oily and black, but Number 2 is clean after being washed by the leaking diesel fuel. Take the cylinder head cover off and check, it only costs a gasket! The line has been known to crack and leak where it joins to the banjo bolt fitting or the gasket may fail. This isn't as uncommon as some might suspect.

[Rattle]

G'day Charlie,

Thanks for taking the time to reply. I agree that the fuel return (leak-off) pipe is the primary suspect.

I removed the valve cover yesterday and found that the banjo bolt at No 4 injector looks a bit "washed".



I replaced all 5 of the aluminum gaskets. Unfortunately, Toyota didn't have a replacement fuel rail in stock, or I would have just replaced it. I did inspect it, but found no obvious cracks or defects (however the joins are braised and it's very hard to tell with the naked eye). Would have been nice to test it, if I had the gear to do it.

I've done about 250km since then, but it's still hard to say for certain that it's fixed (I have my doubts). The engine oil has now been changed 3 times within 1000km, so it's really clean; and the Hilux dipsticks are very hard to read at the best of times, so it's all a bit of an estimate.

It's the usual case - Christmas break, and nothing is open - can't get parts before the weekend. And, of course, the missus has made plans which involves around 900km of driving.... uggh.

[dave g]

Rub same sand paper and scratch the faces of your dipstick will make it easier to read

[ptrl1600]

G'day Charlie,
I removed the valve cover yesterday and found that the banjo bolt at No 4 injector looks a bit "washed".

It looks like you've found the culprit! In my case the area around the leak was easy to identify as being washed and very clean compared to the rest. At least you now know and can monitor the situation, but hopefully it's fixed.

[Rattle]

At least you now know and can monitor the situation, but hopefully it's fixed

Unfortunately, replacing the aluminum "gaskets" did not fix the problem - the engine is still "making oil".

I have ordered a replacement fuel return (leak-off) pipe. If that doesn't fix the problem, I'll replace the fuel pump, injectors and maybe the injector pipes (they're very expensive).

I'll try to keep updating this post for anyone who runs into this issue.

[Rattle]

Rub same sand paper and scratch the faces of your dipstick will make it easier to read

Thanks Dave. I realised how silly I sounded in posting that issue on the this forum with out doing a search. I found a post on here which recommends twisting the end of the dip-stick by 90deg. It now reads like a normal dip-stick!

[Gipsy]

At least you now know and can monitor the situation, but hopefully it's fixed

Unfortunately, replacing the aluminum "gaskets" did not fix the problem - the engine is still "making oil".

I have ordered a replacement fuel return (leak-off) pipe. If that doesn't fix the problem, I'll replace the fuel pump, injectors and maybe the injector pipes (they're very expensive).

I'll try to keep updating this post for anyone who runs into this issue.

Hey Rattle, it seems that you have found the problem so why look any further at fuel pump and injectors if it's obvious that the return line is leaking. I suggest take that route first. Maybe a diesel specialist can pressure test the line to identify the problem before throwing lots of $$$ at it.

[Rattle]

why look any further at fuel pump and injectors if it's obvious that the return line is leaking.

G'day Gipsy,

You may have overlooked the operative phrase:

If that doesn't fix the problem...

Moreover, just because the banjo bolt looks washed, it does not not definitively conclude that that is the issue. It's also possible (though, unlikely), that there is more than one issue.

The post was just my thoughts on how the troubleshooting and repair might progress if the issue isn't resolved by replacing the fuel return line. In my experience, it's often a good idea to have a Plan B, in case Plan A doesn't work.

[ptrl1600]

Hi Rattle,
I'm not very familiar with the Hilux diesels, so not sure if this is possible, but can you run the engine with the engine cover off?? it might be the best or only way to see the leak.

[Gipsy]

With 28 thousand PSI in the pipes it won't be hard to spot!

[Rattle]

... can you run the engine with the engine cover off?? it might be the best or only way to see the leak.

No, unfortunately. The intercooler and injector lines are removed in order to get to the valve cover. Theoretically, I guess you could reinstall the injector lines and run it without the intercooler, but it's not something I'm prepared to do.

[ptrl1600]

No, unfortunately. The intercooler and injector lines are removed in order to get to the valve cover. Theoretically, I guess you could reinstall the injector lines and run it without the intercooler, but it's not something I'm prepared to do.

Fair enough! I guess the easiest way is just to replace the spill line and monitor it again.
In my case, there was a leak in the line where it joined the banjo bolt fitting, but it wasn't visible to the naked eye. My guess would be that with all the vibration in a 4 cylinder diesel, it could crack over time and I did spend a fair bit of time idling over the years.