Internal engine cleaning

Posted on May 12th, 2008 in diesel,Driving Emotion,Peugeot by Julian Edgar

In recent articles in AutoSpeed we’ve covered the major benefits of water injection. Without recapitulating those articles in full, water injection can improve power, lower fuel consumption and reduce exhaust emissions.

As recounted in one of those articles, the high pressure water injection system that I developed was tested on both my Honda Insight and Peugeot 405 diesel.

However, I haven’t left the water injection system installed on either of these cars – the Honda’s would have needed too large a water tank (the water injection was being used continuously in cruise) and in the Peugeot, the water injection system did not reduce post-turbo intake air temps as effectively as squirting the spray straight onto the intercooler core.

The testing carried out on the Peugeot involved assessing the intake air temp increase when the car was held on boost up a long country road hill. The hill – a steep 15 per cent grade – is nearby. To do the testing, I simply drove down to the bottom, read off the intake air temp (being monitored by a remote-probe LCD gauge) and then drove up the hill at a constant speed. The temp at the top was then noted, and a simple subtraction showed the temperature increase.

After each test, the water injection system was changed in a single aspect (eg the volume of water flowing) and the test repeated. In all, seven or eight different configurations were tested.

Without any water injection, the intake air temp rose by 40 degrees C. With a variety of different water injection amounts, the intake air temp rose by 37 – 39 degrees C… barely any difference. Then, with the spray onto the intercooler core, the temp increase was held to only 21 degrees C.

Now the reason for writing this blog isn’t to compare water injection with an intercooler water spray – much more testing of different set-ups would be needed to draw major conclusions. Instead, I want to tell you what I noticed after the testing was finished.

During the testing, I’d changed the water injection nozzle to add increasingly large amounts of water. As indicated in the series, the water was being added in front of the air filter, a good safety measure in a diesel that has such small internal clearance volumes. To assess whether too much water was being added to properly atomise and evaporate, I periodically looked at the filter element. With the TN0.4 nozzle directed right into the mouth of the air intake, a lot of water was going into the engine. In fact, configured in this way, the filter element was wet and there were condensed water droplets in the air box on both sides of the element.

So, even though the up-the-hill testing was fairly short-term (say an hour or so), plenty of water had been going into the engine.

Testing finished, I removed the water injection system.

It was over the next day or so I noticed the difference. The Peugeot pulled better at low revs and clearly made less smoke. This wasn’t the stuff of imagination: this was the case.

So what was going on? Many independent tests over the years have shown that water injection keeps the insides of an engine cleaner. That is, the carbon build-ups in the combustion chamber are softened and removed by the action of the water (obviously turned to steam!).

My guess is that the water droplets that had been flowing into the Peugeot’s engine had acted in this way, removing carbon build-up and so promoting better combustion (eg through changes to crevice volumes).
It will be interesting to see how long the effect lasts; perhaps a regular dose of water will be obligatory…

37 Responses to 'Internal engine cleaning'

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  1. Marty said,

    on May 12th, 2008 at 10:32 pm

    I’ve certainly heard similar comments – that water injection cleans the cylinder bores, valves, etc.
    However, I suppose the only way to really confirm it is to take the head off before and after a dose of water injection, to check the state of the engine internals.

  2. Lucas said,

    on May 13th, 2008 at 8:01 am

    An alternative: I routinely let old poorly maintained engines sip water via a vacuum line and then a small quantity of naphta based injector cleaner/Moreys Upper Cylinder Lubricant. The before and after difference in terms of engine performance can be quite significant. Lots of smoke might come out of the exhaust though. In the States, some people use Seafoam to clean their engines this way once in a while and often report good results. Of course you can ruin your cat converter, but hey, if it’s an old banger bought cheap, it doesn’t matter.

  3. Peter said,

    on May 13th, 2008 at 12:36 pm

    J, just to add another pump option, take a look at airless spray painting units. I think some of them claim pressures of 150 bar and they are designed to operate with water based paints. Higher pressure might give you the confidence to inject after the turbo in your Pug. I’d be interested to see these results.

  4. Paul said,

    on May 13th, 2008 at 4:29 pm

    I can second that. I’ve been using water injection on a MY95 WRX for about 2 months.

    When my big end bearings got damaged and the engine was opened up, it was very clean inside. No carbon buildup at all. The interior of the head was a light gray with the exhaust valves having a slightly darker gray.

  5. Sam said,

    on May 13th, 2008 at 10:24 pm

    According to my thermodynamics lecturer, its due to the ‘explosive’ nucleation (which is one of the ways bubbles form), which creates swirl and better mixing in the combustion chamber, leading to a cleaner burn, less carbon deposits etc. Apparently water injection in diesel engines to improve the combustion process has been quite widely studied. Whether this phenomenon is what Julian observed, well anyones guess is as good as mine.

  6. Bob Wilson said,

    on May 13th, 2008 at 11:14 pm

    Could one combine the water system with too ‘cold’ spark plugs to test this hypothesis? Put ‘cold’ plugs in an engine and run until they start to ‘coke up’ and then see if the water injection system ‘cleans the plugs’ in situ.

  7. Jim McNally said,

    on May 14th, 2008 at 2:59 am

    There is no question that water injection keeps engines cleaner and reduces detonation at high boost, allowing you to make more power with less fuel. People have used water injection successfully for over 50 years in high performance engines. There is one thing to watch out for, though.
    Years ago I had a neighbor who had been an aircraft mechanic in WWII on a carrier. Many of the aircraft used water injection to prevent detonation at full power. But on engines with aluminum heads, he said they had a major problem with the steel ends of the spark plugs rusting and then stripping out the threads in the heads when removed. Sometimes they could re-tap them, but often they had to discard the heads completely, because they would never hold compression levels again.
    So if you are going to use water injection with an aluminum head, you might want to test your plugs to see if the threads will rust first.

  8. pete_mac said,

    on May 14th, 2008 at 9:52 am

    In regards to Lucas’ comment regarding Seafoam, the ‘Subaru Upper Engine Cleaner’ product (part no.SA459) is an excellent product available in Australia which has a foaming agent and solvents to help dissolve carbon deposits inside the engine. It can be used on all engines and is very effective. Bars Leaks manufacture the product. Ford now use and recommend the same product, albeit with Ford labelling.

  9. Ben said,

    on May 14th, 2008 at 4:48 pm

    Julian – In regards to cleaning the engine regularly.

    A friend of ours had a Landcruiser with a Ford 351 Cleveland in it. Every 3 months or so he would warm the car up, hold it at about 1/4 throttle, and slowly pour a glass of water down each primary throat of the carby (dual plane manifold with a Carter on top). During the process (and for a small time afterwards) a mix of water, steam, and carbon would come out the exhaust (possibly too much water?). But afterwards the engine was far more responsive, powerful, and (presumably) economical, with that effect declining until he did it again.

    It’s possible that the engine was badly tuned (why else would it need that regularly?), but it is a good example of water being used for maintainance, and the engine showing a good response to it.


    *ps. When you bought a MK1 Zephyr brand new, it came with an owners manual (as all new cars did, do, and will do). Inside the manual was a description of normal servicing, such as adjusting points, idle mixtures, valve clearances, changing all the fluids (and filters), etc. It also described the need to (and method of) periodically removing the cylinder head for decarbonising the combustion chamber and piston head.

  10. Grant Beaumont said,

    on May 15th, 2008 at 7:54 am

    Julian . Just replaced the head gasket on my JR Vectra which had blown between No.2 piston and the water jacket and consequently the engine had ingested a bit of water.
    No.2 piston was as clean as a new one as were its corresponding valves in the head. An uncontrolled test but does seem to show water injection is good as a decoking agent.

  11. Ben said,

    on May 15th, 2008 at 1:21 pm

    I have the impression he already knew that, this is just the first time he has really experienced it.

    What I would like to know is if there would be much effect on a car with modern engine management. If the car is a ‘cleaner’ design, this carbon problem shouldn’t rear its ugly head as much should it?

  12. Peter Tawadros said,

    on May 15th, 2008 at 11:46 pm

    Having read Ben’s account of his friend’s 351 Cleveland, I went down to my little 1.3 charade tonight armed with a 500mL spray bottle filled with hot water. The charade is completely stock standard, coming up to the big 220000kms, fairly well maintained. Same process, except spraying through the intake snorkel after the filter rather than pouring down a barrel (efi).

    I noticed the exact same excessive steam pouring out of the tailpipe and kept the engine at about 1/4 throttle as well, spraying fairly constantly for about 5 mins.

    Unfortunately being in a built up area with no safe place nearby to do 0-100 tests I couldn’t do a before and after, but seat-of-the-pants feel was that it seemed to be much more responsive and much happier revving out past 5 grand.

    I then did the same thing with my little three-pot charade (1L carby, also more or less stock standard, coming up to the big 240,000kms), and sprayed down the barrel. For a while I noticed the same steam coming out the exhaust, but then after about 250mL no matter how much I sprayed I couldn’t see the same steam coming out. I think this may be because the intake heated up enough to turn the water into steam before it entered the cylinders. Anyhow net result was that I noticed no discernable difference between after water and previous performance. That may just be because the thing put out 37kW when it was new, and bugger all improvement on bugger all still comes out to bugger all…

    So thats 1 positive and 1 negative. I’ll try this with my 185,000 4cyl camry when I get a chance and report on results soon.

  13. Julian Edgar said,

    on May 16th, 2008 at 8:04 am

    People adding water to their engines in this way should be very careful that they don’t hydraulically lock the engine and so damage it!

  14. Ben said,

    on May 16th, 2008 at 9:37 am

    Yeah. I would hate to see someone blame me because they failed to have their engine running while they poured it down, or just dumped the whole glass in.

    I think it’s time for me to give it a try.

  15. Brad said,

    on May 16th, 2008 at 10:15 am

    I use a fuel additive at 1:1000 which works so well that pulling any intake parts off old or new cars I have used it in reveals spotlessly clean. ie. no carbon whatsoever. In every vehicle (car, bike, mower) I or aquaintances have used it in, typically improvements are felt immediately, but gradually increase over several tanks, particularly if the motor is being worked when used..

    Carbonisation is a common problem in old, new, carby, fuel injected cars, bikes, petrol, diesel motors (although not LPG). The old method was to pour half a glass of water down the carby at 1/4 throttle as mentioned, followed by a decent dose of carby cleaner. CHANGE OIL AFTERWARDS as this will contaminate the sump.


  16. Peter Tawadros said,

    on May 16th, 2008 at 12:38 pm

    Yeah actually I guess those points need to be overtly stressed, it is pretty easy to stuff an engine if you don’t know what you’re doing. Knowing full well what could happen, I wasn’t about to lock my engine and I let it warm up to operating temp before I started spraying. I specifically used a spray bottle set on a fine mist spray rather than jet spray, and I periodically took the snorkel off altogether and tapped it out to make sure there were no pools of water accumulating. I sprayed to the point of the engine wanting to bog, then let it revive itself (in a cyclic manner), and made sure it was always spinning faster than idle.

    Its interesting to note that this morning its cold start problem (it starts fine but then sits there at about 300rpm before I blip the throttle) was non-existent.

    On another note, has anyone tried seafoam: – a google search comes up with quite a lot of favourable comment, but the only concrete measured results noted on its benefits is a decrease in particulate emissions. Probably similar to the Subaru Upper Engine Cleaner mentioned by pete_mac.

  17. Ben said,

    on May 16th, 2008 at 1:38 pm

    that additive wouldn’t have much to do with acetone would it?

  18. Brad said,

    on May 16th, 2008 at 1:42 pm

    If you are talking about the one I use I have no idea whatsoever what is in it. All I know is apparently injectors and diesel pumps running this stuff typically are not looked at in heavy transport for 1.5 million k’s when the trucks are sold, so whatever it is it apparently doesnt eat plastic or rubber, which I imagine acetone would do. The only thing I know for sure is the company gets the specific additive package from the states- ie not available anywhere else (that I know of).

  19. Ben said,

    on May 16th, 2008 at 2:23 pm

    it sounds like a pretty good thing.

    What’s it called?

  20. Lucas said,

    on May 17th, 2008 at 1:01 pm

    The main ingredient in Seafoam is naptha. Unfortunately, I don’t seem to be able to find Seafoam in Aus. I heard about the Subaru cleaner but after looking at the MSDS for Seafoam, I concluded that it’s a mixture that has a majority naphta content. At the usual weekend autoparts shop I looked around at the various cleaning/valve fluids and found that Morey’s Upper Cylinder Lubricant. An MSDS search for this Morey’s product made me think that it has naptha in about the same concentration. I sometimes used it mixed with a little ATF, sometimes straight. Most ‘fuel injector’ cleaners that you can buy easily everywhere also has a similar concentration of naptha. The trick to not hydrolocking your engine is to let the liquid sip through the vac line, and NOT suck in a whole lot at one hit! Of course some people recommend that you should let the liquid in a fairly quick gulp to just before hydrolocking and let the engine steep for a few minutes before restarting. Sipping water before and after the naphta treatment has been recommended by quite a few Seafoamers and that’s what I do as well. The engines I have treated always seem stronger and smoother after such treatments – but note, these are usually old engines with more than 100k kms on them, and have not been generally well maintained.

  21. Lucas said,

    on May 17th, 2008 at 1:16 pm

    …addendum to earlier post: I should have said that I had thought that the majority ACTIVE ingredient was naptha (20-35%). The majority component in Seafoam liquid is actually ‘pale oil’ (40-60%). The balance is Isopropyl Alcohol (IPA). Of course, some people argue that it’s the pale oil that’s doing the cleaning. The MSDS for Morey’s Upper Cylinder Lubricant lists ‘naphthenic distillate’ in <60% and doesn’t say much about the balance. The Seafoam can lists “Upper Cylinder Lube” amongst one of its many uses……..

  22. Jay said,

    on May 17th, 2008 at 9:38 pm

    I never thought this would work until reading this site.
    I tried it with my car. 283 000km VK commodore EFI. I bought the car about 230 000km 10 years ago. Oil changes have been at 5000 to 10 000 km. BP ultimate, Mobil Synergy and Shell Optimax/V power fuel used except for emergencies. The engine has been making a deep knocking,clicking noise noticable for about 6 months. For the last year I have NEVER revved it over 3500rpm. On Friday I drove the car to warm the engine up and sucked in about 1 litre overall of water. (I have know idea how much is enough). Then I took the car for a road test in my normal driving style. The engine improved quite noticably. I checked the oil and found oil contamated with water all over the oil filler cap and dip stick except where the normal oil level is. I almost straight away drained the oil and checked the filter. There was no visual signs of water contamination. The oil/water gunk on the dipstick and cap I am presuming is from blowby. I changed the oil and filter then drove and warmed up the engine. The engine was running beautifully so I gave it a good squirt. I revved it to 4500rpm then backed off feeling very happy about how the engine was running after the water treatment until I slowed right down and the knocking in my engine sound much worse (terminaly worse). I nursed it back to the workshop for further checks. The noise appears to be one of the gudgeon pins which I’m guessing didn’t enjoy being connected to the crankshaft rotating at 4500rpm. I don’t think the water was the direct cause. I’m am stripping the motor when I have time over the next couple of weeks. When I’ve inspected the engine I will post my results.

  23. Ben said,

    on May 18th, 2008 at 11:08 pm


    I’m curious what happened to the air-fuel ratio’s during the testing (if they were being measured) on the Insight. If the water was being injected before the air-flow meter, could some of it have gotten on the hot-wire air-flow meter element (if the car uses that)?

    If it did and the air mass measurement was affected it is possible that the air-fuel ratio was effected, however slightly.

  24. Julian Edgar said,

    on May 19th, 2008 at 6:55 am

    I didn’t measure the air/fuel ratio in this testing. The car doesn’t use an airflow meter.

  25. Brad said,

    on May 19th, 2008 at 8:39 am

    I dont know if I am allowed to say its name here, but its called PM800 by PM Lubricants, Australia. They tell me as far as they are aware their mix is the only one of its kind available, all I know is it works as far as I can see.

  26. Steve said,

    on May 19th, 2008 at 7:40 pm

    My father, (ex- mechanic from yesteryear), use to recommend periodically replacing the engine oil with an oil / diesel mix and running the car at idle or just above for a few minutes to clean the engine. Over the years I have tried the mix in various ratios even using straight diesel a few times. Couldn’t say if performance was any better after, nor if the longevity of the engine was compromised… though treated engines (most recently RB30) have not shown signs of unusual wear and the following oil change usually results in slightly cleaner used oil emerging, so it must clean to a degree. It would be interesting (and more relevant), if someone (cite me), were to actually gauge results.

  27. ANdrew said,

    on May 20th, 2008 at 11:14 am

    my uncle used to work at a place that had barrels of straight shellite, and he would re-pack it in containers with minor additives, seel it as wax & grease remover, brake cleaner, carby cleaner, and all those high hydrocarbon tyupe sprays etc… he also would pour it in his oil filler hole and run the engine for a bit before draining, the insides were so clean, also big chunks and sludgy bits would also drain out too.

    he would then re-do the shellite/plus new cheap oil again for a bit, then drain…. repeat untill it came out pretty clean and without the lumpy bits…
    this was on a 470,000km L24e (EFI 240z engine) in a R30 skyline that is still running today…

  28. Ben said,

    on May 20th, 2008 at 12:23 pm

    There’s an interesting thought… Offering a complete internal engine clean with a service. Using crude water injection for the combustion chamber, and a light oil (ie diesel) mixture for an oil system flush.

    My method of an oil flush is a little simpler. I just run the cheapest oil I can find with the right viscosity (spelling?) rating for about 500km. I change the filter twice (once when the cheap oil goes in, and again when it comes out).

    It would be interesting to see how many people can tell the difference.

  29. Brad said,

    on May 20th, 2008 at 12:34 pm

    There are engine flush machines around. PM Lubricants produces the flushing oil for one of them. Basically an extremely detergent oil reuseable up to 5 times, or the machine flushes the motor for I believe just under an hour at a time. What I am told typical results between noticeable improvement to 30% power increase, particularly for old diesel motors such as the hilux and 1HX (?) diesel landcruiser. Obviously it has to be in a fairly bad way already to gain much improvement.

    Another thing to do is just use a quality high detergent, low volatility oil rated S-/C- (ie for petrol and diesel) which will negate the need for additional flushing. Some are more detergent than others.

  30. Ben said,

    on May 20th, 2008 at 12:51 pm

    The 1HZ engine for lancruisers is a relatively late model engine (as far as diesels go). The 2H is that dirty filthy thing fitted to early 60-series cruiser and coasters capable of turning good oil into something resembling black paint in next to no time. That said we have a turbo 2H 60-series and it makes light work of a HX on a heavy trailer.

    Back to the point though, a 30% increase in power? We saw a minimal power increase for the first oil change on the afformentioned 60-series. It required that the sump be removed (the **** that was in it was there so long it wouldn’t come out the sump plug hole at anything more than a slow drip, and held its shape for a short time) to get it all out. I suppose we could have put in some diesel, or even fresh oil, but we didn’t think of that at the time. The oil was changed again shortly afterwards as well.

    Incedentally it’s pretty amazing how loud the engine became after we finally ended up with a semi-clean oil in it.

  31. Brad said,

    on May 20th, 2008 at 12:56 pm


    What I am told is 30% increase has been achieved when engine has been hooked up to the flush machine for however long it takes. Your old 2H I believe would have been a good candidate as that is the sort of condition they were talking about.

  32. Ben said,

    on May 20th, 2008 at 1:17 pm

    I should certainly hope it would classifiy as a clogged up engine.

    Can anyone out there suggest why there would be such a massive power increase? The only way I can see is if the flush process somehow affects the combustion chamber.

    Another way for water injection (on a n/a car with a throttle body anyway) would be to have a small hole drilled just in front of the throttle body idle position (much like the progression drilling on carbies). On light throttle a combination of high airspeed and engine vacuum would draw the water out of the hole and break it up into small droplets. I haven’t actually heard of this being tried, but it seems to be worth a look.

  33. Brad said,

    on May 20th, 2008 at 2:03 pm

    I would imagine it is a combination of freeing up rings, and greatly increasing oil flow reducing friction as now the increased flow through bearings, cam lifters etc. allows for more consistant hydrodynamic lubrication

  34. pete_mac said,

    on May 20th, 2008 at 2:37 pm

    In regards to the Subaru Upper Engine Cleaner, it contains:

    Butane – 10%
    Propane – 10%
    Aliphatic/Aromatic Hydrocarbons (toluene, benzene, acetone etc) – 60%
    Ammonium Hydroxide -10%
    Butyl cellosolve – 10% (This is the foaming additive)

  35. Mitchell said,

    on May 29th, 2008 at 6:38 pm

    Doesnt the water cause the bottom end to corrode?

  36. Ben said,

    on June 6th, 2008 at 5:14 pm

    RE: Spraying water into intake (for once off cleaning):

    I just got around to doing this on my EF Falcon. No idea on results yet, but evidently a 2000rpm idle is not enough with this manifold design. I pumped about 400ml of water in as a fine spray, and it had a few missfires. Eventually I went to up the idle further, and it coughed and spluttered for about 30 seconds before picking up. Evidently water was pooling in the lower part of at least two runners. If I had have opened the throttle quickly, or been doing it at a lower rpm, it could have been pretty bad…

    I thought people should be aware when doing this with a manifold that allows anything to pool.

    Incedentally there is a black patch on my driveway at the end of the exhaust… Do it over grass, lest your better half finds out.

  37. Ben said,

    on June 12th, 2008 at 1:51 pm

    Results aren’t quite what I expected. Open road fuel economy was virtually unchanged, but the engine was quiter at idle. Interestingly enough I noticed a missfire for the first time when it was cold, after having water through it.

    Oh, the 30 seconds was a little long. It was more like 10… But it felt like ages when I had a rough idea what was causing it.