reb78 Posted August 31, 2014 Share Posted August 31, 2014 A while ago I bought an X Eng rad cap to replace the plastic one that got more and more chewed up every time I removed it. Anyway, yesterday, replacing the coolant I found the end of the cap was really corroded making it quite difficult to get the thread started again. Anyone else had this? I'm just running normal ethylene glycol antifreeze. Quote Link to comment Share on other sites More sharing options...
simonr Posted August 31, 2014 Share Posted August 31, 2014 I've never seen that! To be sure, I've just taken mine out - and apart from the blue anodising haven worn off the thread, it looks pretty much as good as! It's just made of ordinary aluminium - the same as a good proportion of your engine! It might be worth having a look at the inside of your thermostat housing to make sure it has not gone the same way! Si Quote Link to comment Share on other sites More sharing options...
reb78 Posted August 31, 2014 Author Share Posted August 31, 2014 Yeah. I was worried for because of that! What on earth could cause it? About three years ago I cleaned the whole system out flushed with copious amounts of fresh water and just replaced with normal blue antifreeze. It's been done again since then. The reason the system was drained (only partially) this time was to do the timing belt. There was some corrosion/crystalline build up around the pipe fittings to the water pump/thermostat housing, but nothing appeared to have dissolved! Quote Link to comment Share on other sites More sharing options...
Team Idris Posted August 31, 2014 Share Posted August 31, 2014 What on earth is maybe the answer, or, which bad earth? I'd re-work the engine earth so it goes direct from block to battery without any losses. (clean the joints or, maybe it hasn't got one?) Quote Link to comment Share on other sites More sharing options...
reb78 Posted August 31, 2014 Author Share Posted August 31, 2014 I'll take a look at adding another one. Definitely one from gearbox to battery. Where would other earths be on the 200tdi block normally? Pretty sure there's one from block to chassis behind the alternator, but will check. Quote Link to comment Share on other sites More sharing options...
WHO4 MUD Posted August 31, 2014 Share Posted August 31, 2014 right next to the passenger side engine mount. or at least this was the case with my 200 when I had it.... Quote Link to comment Share on other sites More sharing options...
reb78 Posted August 31, 2014 Author Share Posted August 31, 2014 Yep. They are all there. I will clean them up, but there are no electrical problems to speak of (only thing that springs to mind is that the voltmeter flicks back and forth in time with the indicators, but cleaning the two earths above has never helped resolve that...I need to do the ones on the bulkhead) Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted August 31, 2014 Share Posted August 31, 2014 Richard, has it corroded exactly the same the full 360 degrees? Why would a bad earth cause the problem, surely it would only cause a problem if the plug became part of the earth path? Quote Link to comment Share on other sites More sharing options...
reb78 Posted August 31, 2014 Author Share Posted August 31, 2014 Richard, has it corroded exactly the same the full 360 degrees? Why would a bad earth cause the problem, surely it would only cause a problem if the plug became part of the earth path? Yep. It's pretty even Barry. It's the bit below the rad thread that 'dips' into the coolant that's corroded. I don't remember any corrosion when it was drained and refilled a year ago. I don't know about the earths, I was just responding to the post above. There's no earth on or near that plug Quote Link to comment Share on other sites More sharing options...
pat_pending Posted August 31, 2014 Share Posted August 31, 2014 Looks like it's been acting as a sacrificial anode. Quote Link to comment Share on other sites More sharing options...
reb78 Posted August 31, 2014 Author Share Posted August 31, 2014 Looks like it's been acting as a sacrificial anode. So, should cleaning up/adding some extra earths sort it? Quote Link to comment Share on other sites More sharing options...
simonr Posted August 31, 2014 Share Posted August 31, 2014 My first thought was that it would happen if the coolant were alkaline. The only thing that will attack both the anodising and the Aluminium is an Alkali. An anodised surface is a pretty good insulator - which should resist the effect of bad earthing. I wonder though if some other electro-chemical process is going on inside the rest of the engine, caused by earthing problems, which has caused the coolant to become alkaline? Under normal circumstances, both water and Ethylene Glycol are neutral - Ph 7 so neither should attack the Anodising. Si Quote Link to comment Share on other sites More sharing options...
CwazyWabbit Posted August 31, 2014 Share Posted August 31, 2014 Surely it should be attacking the other Aluminium parts to? Or is it related to the exact alloys used? Or does the increased surface area cause by having a thread accelerate the effect? EDIT: Why do I ask so many questions? .... Damn that's another one! Quote Link to comment Share on other sites More sharing options...
simonr Posted August 31, 2014 Share Posted August 31, 2014 Barry - That's why I suggested looking at the state of other Ali components such as the stat housing. Si Quote Link to comment Share on other sites More sharing options...
reb78 Posted September 1, 2014 Author Share Posted September 1, 2014 Barry - That's why I suggested looking at the state of other Ali components such as the stat housing. Si Like I say though, I've had the pipes off of the other ali bits and apart from a little build up of crystalline material around the hose connections they look ok. The water pump housing is aluminium isn't it? That looked fine before replacing it. Quote Link to comment Share on other sites More sharing options...
timppl Posted September 1, 2014 Share Posted September 1, 2014 This is probably a bit of a shot in the dark, but have you got awire with damaged insulation touching the cap ( even intermittently ) which could cause it to electrolyse? Tim Quote Link to comment Share on other sites More sharing options...
reb78 Posted September 1, 2014 Author Share Posted September 1, 2014 Right, i will clean up my earths, but i'm not convinced they are the problem. I was thinking of buying a couple of these to add in addition to the existing ones: http://www.ebay.co.uk/itm/12-BATTERY-CABLE-EARTH-EARTHING-BRAID-STRAP-TERMINALS-/181225766896?pt=UK_Cars_Parts_Vehicles_Terminals_Cabling_ET&hash=item2a31e5bff0 Can anyone think of any problems if i went engine to chassis and then chassis to gearbox (where the battery negative is connected)? That ought to be sufficient? Maybe a third from bulkhead to chassis as well?? Quote Link to comment Share on other sites More sharing options...
simonr Posted September 1, 2014 Share Posted September 1, 2014 Personally I think the best earthing strategy is to connect the battery negative directly to one of the starter motor mounting studs, then use a braid to connect from there to the chassis. Where the battery normally connects to the chassis, use braid to connect the chassis to the gearbox or transfer box via any suitable bolt. The starter motor draws the highest current - so it makes sense to give it the best earth. Anything else which draws high current (winches, inverters etc) run positive and negative direct to the battery without relying on the chassis or engine for earthing. This approach has served me well over the years! Si 1 Quote Link to comment Share on other sites More sharing options...
Team Idris Posted September 2, 2014 Share Posted September 2, 2014 Given the chance, I wouldn't use the chassis for an earth point at all, but this can only really be done on trailers. So I use the Simon method. On the van the cut-off is on the battery negative line. Then its wires aren't at risk of shorting on their run to the cab. It was easy to do while I laid in the new earth line. Stray earths go all roads. If some of the starter electrons decide there is a chance of getting to the battery via the rad, then off they go. I normally assume my vehicles are trying to destroy themselves and work back from there A bloke got sent down for selling zinc anodes that fitted on your car body to prevent rust. (fair I thought). But Pirate4x4 had an interesting read on zinc anodes immersed in the rad water. They were trying to reduce rust in race cars that weren't allowed antifreeze. It set me thinking, as I have a lot of different metals in the rear-rad install. Quote Link to comment Share on other sites More sharing options...
reb78 Posted September 3, 2014 Author Share Posted September 3, 2014 I've just checked my coolant pH and its 7.65, so pretty neutral. I guess this points to the earth issue presuming the coolant isnt supposed to be more alkaline than this? I'll order some of those earth straps and add them from starter to gearbox rather than relying on it earthing through the block and connections and take it from there. Quote Link to comment Share on other sites More sharing options...
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