Broken heater pipe connector

[2cams70]

Hi Guys,

Does anyone know the thread size used for the heater hose connector that screws into the front cover of a Lotus Twin Cam? Mine was pot metal and has broken off flush with the cover. I've had a bit of a go at it with a Dremel but have probably made things worse for getting it out although I haven't damaged the threads yet.

I was thinking one of these kits available on Ebay might do the trick. It's meant for a Chevy pickup truck and is designed for a 1/2 inch - 14 NPT thread.

http://www.ebay.com.au/itm/Lisle-tools- ... repair-kit

Any advice would be appreciated

Regards

[prezoom]

Try your local home supply store. Like Home Depot or Lowe's here in the US.. In the plumbing department, they have a variety of tools for removing a broken threaded portion off pipe where it enters a fitting. One type uses an off set pair of dowels that jam themselves into the broken off part. Another, mostly used for plastic pipe, is a tapered, multi bladed taper that is driven into the offending part. Sort of like a reverse reamer. I have used both with good results.

[Panda]

Hi,
Mine Is 3/8"- 19- BSP thread
cheers Alan P

[john.p.clegg]

So is mine,nominally 3/8 BSP even thought the diameter is 21/32"...

http://www.bspt.co.uk/

John

[RichC]

thank you John for that posting . it's amazing what infomation you find on this forum !

[2cams70]

Thanks guys for your information.

I stripped the timing cover down further today using the press at work and unfortunately it doesn't look good. There's a fair amount of corrosion and deep pitting where the adapter fits. I've attached a picture and want to ask what you guys think. Is this too far gone? Surprisingly there weren't any water leaks prior to the engine stripdown. The PO had put a copious amount of silicone around the adapter ring and it's "O" rings before installing it.

Has anyone repaired the corrosion in these by welding and re-machining? Welding is beyond my list of skills but I know miraculous welding repairs can be done to Lotus heads and this would seem simple by comparison.

It seems a bit of a waste to throw it away because it's good otherwise - apart from the broken heater fitting.
New ones are around $AU500 and this engine so far has been a severe wallet bleed! If I do replace the cover I may as well go down the Burton cartridge water pump route (slippery slope again!).

Regards.

[S3FHC]

try this repair kit in the first instance...


http://www.ebay.com.au/itm/THREAD-REPAI ... SwEK9T~z-M

the helicoil tap is used to cut a larger thread in the damaged area, this is then followed by the insertion of a spiral "insert" (more or less a corrosion resistant thread) which is far stronger than the original thread cut into the alloy casting.

(I wouldn't have the part welded unless it's the last resort)

regards,

Mark.

[S3FHC]

ps - you will also require a drill bit to open up the damaged threaded area to suit the helicoil tap..
they are suggesting 17mm which may mean a visit to a machine shop as 17mm is too large for most DIY kit

Mark

[2cams70]

Hi Mark,

I was wondering what you guys think about the corrosion around where the pump itself sits too (see second picture - I should have uploaded it as the first). If this makes the front cover a write off then I won't need to worry about removing the broken heater outlet.

Regards

[john.p.clegg]

Mark
The water pump corrosion should be no problem as it has an insert .

John

[2cams70]

Trouble is that corrosion is right where the O-ring is supposed to sit.

[512BB]

'I was wondering what you guys think about the corrosion around where the pump itself sits'

What corrosion 2cams? The area around the pump looks like it will clean up to AS NEW to me. I have seen and used so much worse, yours will be fine.

Re the water take off hole thread, I am sure it will go again, with care. If you do not have the tools, take it to someone who does. The front cover needs to be mounted 100% horizontally on the bed of a pillar drill, so that you are going in squarely. Increase the size of the drill up to the size of the original threads in the cover. You will probably then be able to chase round the treads to remove whats left of the old union. Clean up with the correct tap.

If this method does not go to plan, you have lost nothing, as you can then fit an adaptor.

Best of luck with it.

Leslie

[2cams70]

Thanks guys. I can kinda see now why proper sealing of those "O" rings isn't so important. Any coolant that leaks past will get stopped at the interface between the front cover and the backplate provided you have put some sealant there because there is no gasket as such.

I think the original design intent however was for the "O" rings to do the sealing rather than the front cover/backplate interface. I imagine there must have been quite a few cases of coolant mixed in with oil back in the day when these things were no longer new and some corrosion had set in and before RTV silicone was around. The coolant stagnates at that point hence the localized corrosion. Good old Lotus design - here for a good time not a long time!

I'll think I'll leave the broken heater hose connection to be attended to by my engine machine shop rather than risk damaging it further.

Regards