IS250 Carbon build up? Oh yes!

[Mike_Mac]

As i'm sure all IS250 owners know, the DI nature of the 2.5 V6 engine means that some degree of carbon build up is inevitable.

I've just replaced the engine in the IS250 project I have ongoing, from a 183K mile, neglected and pretty beat-up engine, to a 29K mile, excellent history and good condition engine.

So, for those who're interested, below is the intake and valves from the 183K engine:

Not too nice!

And here are the intake runners and valves from the 29K engine:

Not as much, the runners are pretty clean, but there's a fair buildup on the back of the valves already. This is what they looked like after a lot of manual cleaning:

 

 

Not perfect, but a lot of the remaining gunk was quite loose and soft, so should clear even more once running.

So! It looks like it's not a bad idea to get your intake off every so often and see if it's worth givign it a bit of a freshen up!! 😄

I would also recommend walnut blasting vs DIY unless you're a bit of a masochist!

[Mr Vlad]

Nice one Mike 👍. No one can argue now that our engines coke up even in just 29k miles.

Personally I looked into those DIY sprays and came away none the wiser as nothing was conclusive. Walnut blasting is the way to go but as of a year and a bit ago not many did it.

[Mike_Mac]

10 minutes ago, Mr Vlad said:

Nice one Mike 👍. No one can argue now that our engines coke up even in just 29k miles.

Personally I looked into those DIY sprays and came away none the wiser as nothing was conclusive. Walnut blasting is the way to go but as of a year and a bit ago not many did it.

The DIY sprays, on their own, do very little IMO. You're talking about carbon that's been baked onto the intake and valves over hundreds of heat cycles and nothing's going to do the trick unless it's incredibly strong - and would probably not be good for the rest of the engine! 

Where they do assist, is when you're using them to aid manual cleaning, which is what I did above. Which is very time-consuming and still leaves remnants. It is cheaper, though, but unless price is the driving factor, I's go for walnut blasting! 

[Mr Vlad]

Yes Mike and that's where no conclusion came about. Far too many fake type videos showing before and after and using a boroscope. The most stupid fake one was with a guy with an accent almost unique using the same ruddy car time and time again using different sprays. The most convincing ones showed what they call heat soak. Spray the stuff in when the engine is hot then leave the stuff to 'do it's thing' then start the car up and enjoy the plumes of white/grey smoke billowing out of the exhaust. 

I just wish I had the nowse to strip a top end down but at my age I just ain't got it anymore. I will however buy a boroscope and take a plug or 2 out and have a look to see what's there and go from there. I'm hoping in that since new my cars had its oil changed at around 4.5k mile intervals that the coke might not be bad.

I'll look into walnut blasting this week to update where does it.

[Steven9233]

Very interesting ! Thanks for posting this . I will be changing  oil every 6 months as did previous owner , I only use super unleaded so I hope this is helping to reduce carbon build up risk . Maybe it’s not . I also make sure the car gets a motorway blast at least every month   Car has now done 39k .  Intend to keep for long time as I’ve had far too many cars and wasted lots of money , also anything newer in Lexus world seems to be hybrid , I’d rather boil my head than buy a hybrid , but guess I’ll have to one day . so I’m interested in looking after the engine best I can . 

[Mike_Mac]

1 minute ago, Steven9233 said:

Very interesting ! Thanks for posting this . I will be changing  oil every 6 months as did previous owner , I only use super unleaded so I hope this is helping to reduce carbon build up risk . Maybe it’s not . I also make sure the car gets a motorway blast at least every month   Car has now done 39k .  Intend to keep for long time as I’ve had far too many cars and wasted lots of money , also anything newer in Lexus world seems to be hybrid , I’d rather boil my head than buy a hybrid , but guess I’ll have to one day . so I’m interested in looking after the engine best I can . 

Sounds like a good plan - these engines definitely don’t like dirty oil! 

Ref carbon build up - so long as it’s being well serviced, I wouldn’t worry too much - all DI engines do it and my only suggestion would be to consider cleaning the carbon out every 60+ thousand miles or so. Plenty of places do walnut blasting, and there is a DIY option if you’re a bit masochistic too!

[H3XME]

2 hours ago, Steven9233 said:

Very interesting ! Thanks for posting this . I will be changing  oil every 6 months as did previous owner , I only use super unleaded so I hope this is helping to reduce carbon build up risk . Maybe it’s not . I also make sure the car gets a motorway blast at least every month   Car has now done 39k .  Intend to keep for long time as I’ve had far too many cars and wasted lots of money , also anything newer in Lexus world seems to be hybrid , I’d rather boil my head than buy a hybrid , but guess I’ll have to one day . so I’m interested in looking after the engine best I can . 

Motorway blast won't really do much for it to be honest. It's not like cleaning DPF on a diesel.  What's better is taking it out on some fun welsh/b roads and have some fun stretching its legs over the full rev range. You need to build up a lot of heat which you won't do from a motorway run sat at 2.5k rpms. You can do it within national speed limit on fun roads by just redlining the car in second gear.. I do it just for fun anyway, but it's also beneficial.. that's how I justify it myself🤣

[H3XME]

@Steven9233 @Mike_Mac I would recommend these two products. Put them in a tank of super unleaded every few months and you'll be fine. It's an additive, not a miracle. I worked for Liqui Moly and know the products. They do work, (can't comment on similar products from other brands), but bear in mind it's a not a magic fix. It does help with cleaning, but more importantly it's a preventative measure. People tend to turn to additives when it's too late and then complain that they don't work.

Valve Cleaner - https://www.amazon.co.uk/Liqui-Moly-1014-Valve-Cleaner/dp/B00295G91S

Injector Cleaner - https://www.amazon.co.uk/Liqui-Moly-Injection-Cleaner-300ml/dp/B0096Y6OII

Injector cleaner will have an immediate effect and will be noticeable straight away IF there is something not right. If your car is okay, you won't notice any difference, but like I said, it's about prevention rather than repair. My friend's Astra turbo petrol was not boosting properly when you booted around it 3000RPM. It was ran on sh*t supermarket 95RON fuel all its life. A tank of super unleaded and the injector cleaner and it was working properly again.

[Steven9233]

That’s good enough for me , sound Advice on experience  . Thank you Added to my basket , 

[Mr Vlad]

Nothing added to a tank of petrol will help clear carbon off the inlet valves tops and seats. Nothing.

Those additives above help clean fuel injectors.

As for taking a motorway blast once a run as Lucas stated that's no good really. However. Go on a motorway blast in manual mode and select gear 3 and stick to 70. That'll rev at about 4k. Do 80 and the revs will be about 4.5k. Keep it on cruise control. A while back I did a run from Manchester to Leeds in manual mode. Did 80 most of the way and red lined it a good few times. Didn't do the car any harm but it did kinda clear some cobwebs. Sounds fabulous doing that.

[H3XME]

44 minutes ago, Mr Vlad said:

Didn't do the car any harm but it did kinda clear some cobwebs. Sounds fabulous doing that.

Definitely. I feel like some people are scared to take the car to the red line. (maybe it's a woman thing) It won't hurt when it's fully warmed up! 

[Mr Vlad]

True Lucas. The day I did it on I kept it in 4th and on red line for minutes at a time. Fun was had 😁

[TadasC]

As per @H3XME recomendation I have tried different product of Liqui Molly. He has generously given it to me to try and i think it worked. Its an Intake valve cleaner but its the one you spray into intake when the car is running. Did it when the car was running, holding it at 3.5k rpm and sprayed hole bottle inside the intake. Car was pouring some white smoke out and then took it for a test drive in manual mode and keeping revs high. It mainly helped to get rid of the egg smell from the cats it probably cleaned some of the carbon as well. But will take intake off soon so will see how 110k engine looks on the inside.

Thanks again @H3XME

[Mr Vlad]

Hi Tadas. How did you spray the stuff into the inlet? Through the throttle body or into that vacuum pipe Battery side of the inlet manifold?

Either of those methods are the only ones to 'work' but manually clean the valves and inlets is the best.

I look forward to seeing your photos of your cars inlet when you take it off. Don't forget to take lots of photos. 

[TadasC]

Hi Vlad, the only way to spray it in there was through the breather hose as if you remove the inlet hose the car just dies.. Will be interesting to see how it looks, anyway im determined to do some manual cleaning.

[Spark plug]

On 1/25/2023 at 8:46 AM, H3XME said:

Motorway blast won't really do much for it to be honest. It's not like cleaning DPF on a diesel.  What's better is taking it out on some fun welsh/b roads and have some fun stretching its legs over the full rev range. You need to build up a lot of heat which you won't do from a motorway run sat at 2.5k rpms. You can do it within national speed limit on fun roads by just redlining the car in second gear.. I do it just for fun anyway, but it's also beneficial.. that's how I justify it myself🤣

Italian tune up is what its called lol

[Steve_Pr]

Interesting to read the comments on the carbon issue. My feeling is that how you use and maintain the car must greatly affect what level of build-up of carbon you get on the intake valves. My 2006 250 has 165k miles and had one Terraclean at 100k miles. I've recently taken off the intake plenum to sort out a coil issue and with hesitation (no pun intended) decided to take a look at the intake valves - pleasantly surprised to still see the back of the 'metal' valves and not a thick layer of carbon deposits. I can only put this down to very few short journeys over the life of the car, religious 10k mile oil changes with a good quality synthetic and keeping everything in good order - including cleaning the PCV from time to time. I do a few trips each year with 8-10 hours on the motorway in one day and do pour in some fuel system cleaner, so maybe that also helps, although as someone already said I'm not sure it will do much for the back of the intake valves. Maybe an extended heat cycle helps.

As an aside, since doing very long extended journeys over the last few years the 'normal' oil consumption has steadily dropped to virtually nothing needed between changes. So it would appear any carbon build up on the rings may have been significantly reduced? 

It really is a very well engineered car in my view, and has cost me very little to maintain since buying it new. Other than one rear exhaust backbox nothing else has dropped off over the last 18 years!

[GMB]

I remember the days when we would pour a can of redex down the carb intakes and enjoy leaving a white smokescreen on the road for a mile or two.  Nowadays less anti-socially I use V power and a very occasional thrash through the gears in the hope that it cleans things better. The car seems to run exceptionally well, burns no oil and has no smoky exhaust, good mpg and good performance so fingers crossed.