dissolving water ports in cylinder head (lots of pics) - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• dissolving water ports in cylinder head (lots of pics) by rubadubdub on 24 Feb, 2008 10:06
• Thought this might be of interest to you guys. I had remove the head (thanks for the help rich) on my gtd as it was pressurizing the coolant. It has been a little smokey and used oil and water ever since i bought it a year ago. More recently it'd been getting increasingly worse up until it completely overheated (first time) 2 weeks ago whilst driving down the motorway.
  
  The gasket didnt look too bad, no hugely obvious failed points but the guy in the machine shop who checked the head for warpage pointed out that lots of the water ports were eaten away.
  
  He said it was caused by using just water without enough proper coolant and the heat caused it to become acidic and eat away at the aluminium. The head was brand new 3 years ago and when i bought the car last year the coolant was a filthy brown colour so i changed it for 50% ethyl glycol, but presumably some damage had already been done. Interestingly he said this also happens to ethyl glycol coolant over time which is why it should be changed every 2 years.
  
  He also said that the coolant and engine can act like an electrolysis cell and metal dissolved in one area can get deposited in another with certain combinations of metals in head/block which favour such reactions. Anyone heard this before?
  
  I 'm just amazed this could happen in such a short space of time, especially seeing as i changed the coolant when i got it. Does it look like this could be the cause of the pressurized coolant?
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
• #1 by jtanguay on 24 Feb, 2008 10:29
• thats weird!
  
  I've heard of electrolysis, but that looks a lot different than electroplating... it looks as if it was always that shape.  also you need a 12v source for electrolysis, and there is only a ground source on the block.  otherwise you would be producing hydrogen & oxygen inside the coolant system which might not be good.
  
  hey where's the cracks between the valves  :lol:
  
  you might want to skim the deck and plane the head then put on a new hg.  that should get you going.  i'm liking that new antifreeze thats on the market... it seems to have some red litmus dye in it that changes colour when it becomes acidic... its practically idiot proof although you can purchase some litmus papers from a pool supply store to check your own coolant.  who knows maybe you need to flush your coolant earlier because of contamination from combustion gases?
• #2 by Vincent Waldon on 24 Feb, 2008 10:30
• Cool pictures...thanks for posting them.
  
  {WARNING: geeking-out alert !!}
  
  When I saw them and noticed that it seems to be the sharp corners that are being attacked it reminded me of another factor at play in the diesel cooling system environment... cavitation.
  
  http://findarticles.com/p/articles/mi_m0FZX/is_8_65/ai_55993919
  
  In my early diesel days I remember warnings flooding the Internet about a very popular brand of Prestone coolant that was fine for VW gassers but was prone to cavitation and therefore causing issues.. for a while "diesel compatible" was a label you needed to see on the coolant bottle.
  
  As far as I understand most modern-day coolants are diesel-compatible and so  already contain anti-cavitation additives but presumably those additives wear out over time.   Vendors like Amsoil will sell you anti-cavitation additives in a bottle... generally marketed to trucking fleets etc.
  
  Just one more reason to be diligent with cooling system maintenance I guess.
  
  
  
  Vince
  
  
  One more geeking-out point... cavitation is evidently a serious concern inside the injection pump as well... because of the pressure waves caused by the  injection stroke.  The Bosch diesel bible has a couple paragraphs  on things Bosch had to do to reduce the impact.... special metal coatings in certain places, changes in chamber shape to reduce sharp edges, etc.
  
  Isn't it amazing that these things run at all... given everything that can go wrong ??!!!  ;-)
• #3 by jtanguay on 24 Feb, 2008 10:35
• isn't the cavitation caused by high acidity of the coolant?  or exhaust gases contaminating the coolant system?
  
  hmmm guess its a bit more complicated than that... damn these extremely high combustion pressures!!!  :lol:
• #4 by tigman on 24 Feb, 2008 17:33
• and how about a test to chech the prestone itself , if it containe some contaminant ?
  
  If the cooling systems was clean whith some base like drano or somthing similar and poorly rince  you just see the result of a sloppy job . aluminium react very badly to base solvant (caustic).
  
  Ed
• #5 by bigblockchev on 24 Feb, 2008 17:59
• I'm thinking that at some point in it's life the engine had pure water in it or really old antifreeze with worn out corrosion additives . I usually don't see that much red rust on the head gasket. If someone did a rad flush and didn't  flush out the stuff properly that might account for it also. Rad flush is  an acidic substance. Do a ph test on the coolant if you still have a bit you can get ph test strips from antifreeze suppliers or big diesel shops like Finning. Cheers Dan
• #6 by clbanman on 25 Feb, 2008 09:17
• Below taken from   http://www.motorradiators.co.uk/electrolysis.html
  
  Electrolysis Corrosion
  Electrolysis is a highly desructive reaction casued by the passage of electrical current through coolant which destroys its corrosion prevention properties. It is a menace that attacks radiators and heaters and can destroy an entire engine within 12,000 miles. Electrolysis occurs when electrical current flows through engine coolant in search of ground. It is most commonly caused when an electrical component or accessory somewhere in the vehicle loses ground usually from a loose or broken wire. When electrical devices lose their normal electrical path to the chassis or battery ground the current seeks out any failure route. In most cases of radiator or heater failure loose or missing grounds can be traced to electrical cooling fans or relays. Another cause is bad ground wire from the engine to the chassis.
• #7 by boosted_diesel_84 on 25 Feb, 2008 09:58
• this is why you also need to run pure, distilled water, no tap water!
  
  you say that head was "new" a few years ago, do you mean remaned, or "brand new", because, no offense, if it was brand new, its probably a chinese knock off, that would of been made from cheaper materials and bad tolerences that would have caused this to happen so soon.
  
  sorry to hear that though!
  -Jack-
• #8 by jimfoo on 25 Feb, 2008 10:22
• You could always run Evans coolant. No water, no corrosion, no boiling.
• #9 by zukgod1 on 25 Feb, 2008 10:35
• Quote from: "jimfoo"

  You could always run Evans coolant. No water, no corrosion, no boiling.

  
  
  I agree, I need to find a place to buy it here..
• #10 by rubadubdub on 26 Feb, 2008 02:50
• Thanks for your replies guys. Tinternet was playing up yesterday and i wasnt able to log on.
  
  jtanguay - No cracks! At least there some good news.
  
  biglockchev/tigman - Cant test any coolant unfortunately as its all drained. It turned a lovely grey colour during that last trip which i guess was due to contamination by the exhaust gases. Wouldnt this therefore make tests after the event a little inaccurate as my common sense is thinking the coolant would have been pumped full of higher co2 gas from engine so pH would have altered.  What i should have done is check it months ago when i started loosing coolant! That red colour on HG was the colour of the coolant when i got it so i think you're both right, something not quite right was put in it.
  
  clbanman - cheers for the info. This has happened in about 12k ish miles so i'll check the grounds on the car. The guy neglected to mention that you needed some wandering electricity for this to happen and my A level chemistry is little more than a distant memory (mainly of trying to set fire to magnesium ribbon whenever possible).
  
  boosted_diesel_84 - No offence taken The head was  brand new and has 'AMC' stamped on it, but the invoice lists only a VW part number so not sure where its from.
  
  zukgod1/jimfoo - dont know if we get evans coolant over here. Presumably anything is better than what was in it! Random fact from machine shop guy, although not sure how he knows it : F1 engines apparently use distilled water for coolant as it carries heat better than ethyl glycol. Great for a track no doubt, but rubbish for sitting on your drive in winter.
  
  My OPTIONS are to
  1. get this one welded around the water ports that are eating into the gasket rings around the cylinder (as recommmended by machine shop) or..
  2. Get a 2nd hand head from a scrappy as cant be sure what else is lurking beneath... both would be skimmed flat.
  
  Which do you reckon im best doing? Its swings and roundabouts i suppose.
• #11 by jtanguay on 26 Feb, 2008 03:08
• find a shop that does head repairs... it might just be easier to have this head fixed.  if you buy one from a scrap yard, it might need new parts like lifters, valves, etc.  and if its warped there is more work needed than just skimming the head.
• #12 by jimfoo on 26 Feb, 2008 06:54
• http://www.gearfox.co.uk/evans.html Just to warn you though, it's expensive compared to regular coolant and you have to get their prep fluid to remove all traces of water from your system. It is thicker and doesn't carry as much heat, so it runs hotter, but from my experience since it doesn't boil like water mixes, that isn't a problem.