Tom_Arundel Posted July 26, 2022 Share Posted July 26, 2022 My 2010 sigma steamed to a halt at Aldi`s yesterday, where I bought some water to fill it up. I thought it was the head bleed hose joint but today I found it was the head core plugs had corroded through. The spark plug gallery was entirely full of water which found its way up through the cam cover and exited at the back of the head adjacent to the bleed hose. It never misfired which was amazing! I removed the cam cover and pressurised the water system and a jet about 2ft high came from the rear core plug ( between the spark plugs). Core plugs came out ok, they were so thin that I just pushed a screwdriver straight through them. So tomorrow I hope a visit to Ford will find some new ones and I`ll be back on the road!.I get the impression that the core plugs are above the coolant level in the head and suffer corrosion because of that......So, any coolant stains at the back of the head near the ign. coils may well be core plug problems. I suggest that anyone with an older sigma gets the core plugs replaced......it`s not a big job but a failure could be!P.S. Drove a GT 40 today.....Terrible Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 26, 2022 Member Share Posted July 26, 2022 I don't think that's been described in BlatChat but here's a mention: https://forum.wscc.co.uk/forum/topic/141918-engine-coolant-loss-sigma/What coolant have you been using, please?Jonathan Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted July 26, 2022 Area Representative Share Posted July 26, 2022 I'm sorry to hear of the issue Tom, however you sound resourceful enough to fix things. Link to comment Share on other sites More sharing options...
ptr_drvr Posted July 27, 2022 Share Posted July 27, 2022 There's not a lot of that I understood fully, but the line about the GT40... I'd like to hear more about that! Link to comment Share on other sites More sharing options...
ECR Posted July 27, 2022 Share Posted July 27, 2022 If the core plugs are in the coolant jacket they should always be submerged. The coolant jacket should have no air in it. Has trapped air accelerated your problem or is it just poor quality parts? Link to comment Share on other sites More sharing options...
Tom_Arundel Posted July 27, 2022 Author Share Posted July 27, 2022 Ford say it`s a common problem. I think that the core plugs are above the vent level and air/vapour gets trapped below them hence the corrosion. I shall replace them with home made aluminium bungs.Coolant - Ford red stuff.Ford part F1455107 012242 plug (price suggests they are made of gold!)It was quite funny dis-assembling the Caterham in Aldi`s carpark with customers making comments!GT40 was Virgins (ancient Superperformance) `experience day` car and the worst maintained vehicle I have driven...awful in the wrong sense! `Instructor` and organisation weren`t much better! Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted July 27, 2022 Member Share Posted July 27, 2022 ThanksJonathan Link to comment Share on other sites More sharing options...
Area Representative Golf Juliet Tango Posted July 27, 2022 Area Representative Share Posted July 27, 2022 Awful not awesome? Link to comment Share on other sites More sharing options...
Tom_Arundel Posted July 27, 2022 Author Share Posted July 27, 2022 Awful, not awful as in full of awe which would have been OK Link to comment Share on other sites More sharing options...
7 wonders of the world Posted July 27, 2022 Share Posted July 27, 2022 Tom,what about tapping them and using allen head threaded bungs - not sure what size core plugs they are...? Link to comment Share on other sites More sharing options...
SM25T Posted July 28, 2022 Share Posted July 28, 2022 My feeling is they would be too big to consider tapping the block ? Also, core plugs are designed to be a mechanical 'fuse' ..... Link to comment Share on other sites More sharing options...
Tom_Arundel Posted July 28, 2022 Author Share Posted July 28, 2022 The conversation with Ford suggested that later/other models do have threaded plugs and that the steel ones are a reliability issue.They are 25mm dia. but I will press in a bung with an extractor thread in it and then punch a couple of dings in the rim.`Mechanical fuse`...Well they did that!! Core plugs fill the holes left by the CORE PRINTS during the casting process. Core prints are the support system of the sand core that forms the inside of the casting /water jacket, they extend into and are supported by the outer mould.....Just saying It is back on the road now, took about 4hrs 3 litres of Ford antifreeze £36 !!!!! 4 core plugs £9-60 !!!!! Link to comment Share on other sites More sharing options...
7 wonders of the world Posted July 28, 2022 Share Posted July 28, 2022 These are in the head though and many of these are circa 20mm ish so well within range, many engines already have these tapped and plugged - thinking Alfa's etc.Duratec's are plugged on both head and block too at circa 30mm 1 under No4 exhaust and 1 on the black of the headWhilst they can act as a fuse, though they are there for the casting process, there are many weaker components likely to fail should freezing occur, most wintered engines I've seen have had hoses or housings fail, though seen a couple of cracked blocks but the core plugs were intact, would be interesting to look at the location based on Tom's thoughts to see if cavitation was a possible cause. Link to comment Share on other sites More sharing options...
Tom_Arundel Posted July 29, 2022 Author Share Posted July 29, 2022 Cavitation is possible as the internal surface was eroded but not rusty.......interesting thought Link to comment Share on other sites More sharing options...
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