So pulling the manifold off with the cylinder head is not recommended? Blow torch, don't have one. Acetone and ATF, I can get. Time is the other commodity that I don't really have, so will have to work around that one. I'll let you all know how it went.

7 hours ago, myjalopy said:

So pulling the manifold off with the cylinder head is not recommended?

Yes, it is. Cutting exhaust pipes is not, unless they are unusable.

What I wanted to say in my previous post is don't let a few rusty nuts stay in your way. If there's a will...

Rain has stopped me in my tracks since my last posting, so I've acheived nothing yet. I did drop into another garage this morning on my travels and they also did the 'sniffer' test on a hot engine this time. Oddly, the readings were dramatically different to before. They barely moved past 150 (ppm?) whereas before they were sky high. I know the test was done correctly, because I was there and put my hand over the expansion tank filler hole as the probe was put just inside the neck to make sure it wasn't measuring thin air. The chap still said that it 'indicated' a HG failure though. Yet again, Steel Seal was suggested!

 

I know it sounds like I'm trying to avoid hard work ( maybe I am ) but how can the readings vary so much?

9 hours ago, myjalopy said:

I know it sounds like I'm trying to avoid hard work ( maybe I am ) but how can the readings vary so much?

I can't have a definitive opinion on that since I haven't been there with you but I can list some guesses:

• human factor (respecting rules of operation for the gas analyzer)
• calibration status of the gas analyzer (existence of valid metrological certificate)
• different pollution environment

Whatever the case might be, any reading above 100 ppm hydrocarbons from the coolant reservoir indicates a bad HG (see video at 3:57).

This is a short movie showing the damage on cylinder head and HG due to corrosion. Disregard the audio.