R90 reducer leaking - how to repair.

[Pinger]

Asking advice here on how to cure a leak on my R90 reducer as repair kits at Tinley are 'out of stock', ditto reducers.
Truck threw up a mixture of odd symptoms and it appears that I have a leak between the water and gas sides. I'm currently pressure testing the water side at 5psi and it seems to be holding up. From the other side though, with a hydrocarbon tester at a water port, when I energise the solenoids there is a massive HC reading there.
I've pressure tested the cooling system and done compression tests to eliminate the possibility of head gasket failure. Two symptoms that point to LPG issues - occasionally (and usually after a prolonged period of over-run) on tip-in it goes lean (AFR gauge on dash) and (more tellingly I think) a reluctance when warm to transition between petrol and LPG running. It just quits where before it transitioned seamlessly. Coincidental with the arrival of that is, on shutdown the temp gauge very quickly goes full scale where before it would only go half way between normal running temp and max. This on this engine I'm told will occur if there is a pocket of gas (LPG in my case). Initial investigations uncovered a leaking water pump (coinciding with the poor transition and temp gauge issues). My theory here is that on shutdown the leaking pump drops coolant pressure enabling the passage of LPG into the cooling system. I also detected hydrocarbon in the coolant reservoir.

My problem is how to repair this without a repair kit being available. I've not opened the reducer yet but have the old one and it seems that O-rings are needed. Which, I might be able to source elsewhere if I knew the material they are made from. Another option would be to just slaver the existing ones in RTV. Both O-ring seals and RTV would have to be LPG resistant - and most O-rings and RTV are not petroleum resistant. The O-rings on the old reducer are green in colour which may be a clue to material and the larger on is square section. Photo below is of old reducer. And, just to spice things up, I need this rectified ASAP for work next week!
Any ideas on O-ring material and suitable RTV?

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[Pinger]

Panic over! I've found on-line and ordered a repair kit so the correct parts will be here next week.
I could delete the thread but I'll leave it as it may help someone if ever they have a similar occurrence. An odd set of symptoms and, it was the prompting on another forum to the temp gauge behaviour to check for HC in the coolant. The rest is as per the opening post.

[LPGC]

Glad you found the problem and have parts on the way

[Gilbertd]

Reading through the first post, I realised that I've rebuilt two R90E's but have never opening up the coolant side so the correct O rings will be in the bag of left over bits and pieces and was going to offer to send them to you. Then I scrolled down and read the rest and realised you don't need them......

[Pinger]

Glad you found the problem and have parts on the way

Cheers - you're not the only one!

[Pinger]

Reading through the first post, I realised that I've rebuilt two R90E's but have never opening up the coolant side so the correct O rings will be in the bag of left over bits and pieces and was going to offer to send them to you. Then I scrolled down and read the rest and realised you don't need them......

Thanks Gilbertd - very generous of you. I just got lucky finding another vendor so should be good for next week. I thought I'd be slavering it in RTV but even that idea fell apart as RTVs that can withstand petroleum products are thin on the ground and, take days of curing to reach full strength - and I need to be back on the road by the end of next week at the very latest. O-rings that can withstand petroleum products are pretty specialised too. One of them on the R90 is square section - just to complicate things further. For all those reasons, finding a proper kit was a boon. Now you know all this - don't be throwing out what you have!

I haven't opened up the reducer yet (only the old one) It'll be interesting to see what I find. Just wondering if I'm overly quick in switching to LPG and the seals have been damaged with the cold. Given the odd sequence of symptoms, I'll post here what I find. It can only add to the body of knowledge.

[Gilbertd]

That shouldn't cause a problem, both of mine (and the previous one I sold last year) are left with the switch in the LPG position. They start on petrol then switch over as soon as the revs fall below 1,100 rpm. As the idle air valve on the P38 always opens on initial start, it will always rev to around 1,200 rpm before dropping to normal idle so changes over within a couple of seconds at most. That is even in mid-winter and I've not had a problem other than when the gas we were being supplied with was full of heavy ends so it gummed the internals up until it was warmed a bit.

[Pinger]

I might still yet ask you for your spare O-rings Gilbertd.
Repair kit arrived today and the O-rings are the wrong sizes. The smaller ones (where my leak is I think) are undersize in both diameter and cross-section by 0.3mm and I doubt that they will provide adequate sealing. The larger ones are 4mm larger in diameter than the originals. They are also black - not the green of the originals - which may denote an inferior material.
There's been a design change with the reducers. My old one (that came with the truck) has a brass spigot with machined grooves for 2 x O-rings. The newer one (circa 5 years old) has a plain steel spigot and only one O-ring. A retrograde step surely.
I've contacted the vendor and am waiting on their response.

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[Pinger]

My neighbour friend helped me out with O-rings. The upshot of which is that I can get the reducer back in the car tomorrow and button everything up and be mobile again in a couple of days - hopefully!
While waiting for the vendor to explain why the O-rings in the repair kit are all wrong...

[Pinger]

Follow up post.
Got it all buttoned up and after 135 miles the following day I can safely say all is well. The reducer leak was not from the high pressure liquid side as I'd thought but from the vapour forward bias (that I have set quite high).
One thing that had me worried that I had head gasket trouble was the colouring of the spark plugs. Some had reddish deposits which I feared could be from the red coolant. I'd posted a photo of them on another forum and a guy used to changing plugs on propane powered forklifts said he'd often seen the same. Reckoned it was LPG specific - maybe related to the mercaptan.

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[Gilbertd]

Mine come out looking like yours from number 4. The only time I've ever seen plugs that colour was on a car that was burning almost as much Ethylene Glycol as fuel......

[Pinger]

I'd be more concerned if there was only the one plug discoloured but it is the cleaner plugs which are fewer in number. Unless I have multiple head gasket failure points - or worse, cracked heads. I'm stopping now as I'm scaring myself.