Making the most of the Spring-like weather over the weekend I enjoyed a 50 mile gallop on the Scott on Saturday. Having thoroughly enjoyed myself I decided to
repeat the the pleasure again on Sunday. All went well over the first few miles then slowly the old girl began to feel a bit sick. Power began to drop off & what looked like white smoke began to make its self known at the exhaust end. Pulling to a standstill I noticed the tell-tale signs of leakage from the radiator (which was by now empty) & water dripping from the exhaust (white smoke = steam?). Turning the motor over gently on the kickstart confirmed a reduction in Compression. Now stranded in deepest rural Worcestershire, I decided to put my Peter James Insurance Break Down Recovery Service to the test. Blimey – no phone signal! Despite waving my arms about & climbing a wall to gain a bit of height – nothing doing. By now, pushing the bike toward a distant cottage (uphill, but the only one visible), a kindly chap driving a van stopped & asked if he might assist. Explaining the situation and establishing how far I was from home (estimated approx 12 miles as the cockerel flies) he immediately offered to deliver me & bike back to base by way of his cottage (the above mentioned) whereupon his goodly other-half made me a nice cup of tea!! Never knock a white van-man again I say. What gentlefolk. Tomorrow I will tentatively investigate the damage, although having filled up the radiator earlier to gauge the level of leakage it pumped out by the bucket-full when the engine was kicked over. I suspect from this that there is some internal engine damage, I’m hoping I find a blown head gasket or such but feel very nervous at what I might find. When I turn the engine over which my hand over the filler neck of the radiator I can feel some pressure from what engine compression remains. At this stage it looks like leaking engine compression pressurised the radiator to & beyond bursting point. I will need professional help (surgery) to fix the rad which is a film type manufactured by Northern Radiators, Leeds. Who should contact re this? Graham? Someone else?? All help, advice gratefully accepted. Mike.
Hmmm… In theory, your cooling system is continually vented via the radiator overflow pipe, so pressure shouldn’t build up, unless you have suffered such a seriously blown gasket that it was pumping engine compression into the system faster than the small bore overflow pipe could dump it. You should also still have compression on one cylinder, so it is all a bit odd. Let us know what is revealed when the engine is taken down. Your radiator sounds to be a post-war one, as a 1937 bike should have a honeycomb core radiator. Graham Moag can supply a new one if yours is beyond redemption. Good luck !
Thanks for your response Brian. There is some compression (maybe half of what it was previously). I am assuming that the pressure was pumping faster than the overflow vent could cope with, but this is purely guesswork. I am aware that the rad is not original, it is a replacement made during the late 1940’s I believe, & as such it’s part of the bikes history so I would prefer to stick with it if it can be saved.
I will contact Graham but understood his radiators are of the Honeycomb type rather than Film?
Will update you as & when I know more. I drained the Crankcases of around half a pint of coolant this evening so need to press on with all haste.
Ps People have asked me why I use the Fernyhough moniker. This was my mothers maiden name. She was a niece of the great Eric Fernihough (the spelling within the wider family differs to this day, even through the bloodline is direct.
Hi Mike, it sounds like your problem will either be if you`re lucky just the head gasket, or the head gasket could have gone because the head face has corroded away and is not clamping down on the gasket as it should, or as I generally find the combustion chamber starts to perforate as it corrodes within the water jacket and resembles the surface of the moon, the problem nowadays is finding a good secondhand head, I do a repair by boring out the old combustion chambers and making new inserts that are pressed in. You can also obtain a new head from Roger Moss. Alan Noakes. firstname.lastname@example.org
Thank you so much for your comments. Today, I have removed the head & found the head gasket to be in a pretty awful state so this is the number one suspect so far. Thankfully the head, combustion chambers & mating surfaces appear to be in very good condition with no signs of corrosion. Also, despite losing all coolant I can’t see any sign of damage to pistons or bores thankfully. One thing I immediately noticed is the look of the top surface of the pistons.One looking clean & bright with hardly any carbon or colour, whilst the other looks as I would expect after normal use & mileage (c.3,000 miles) ie light deposits, a little soot but good colour. I should mention that the clean side had a bore full of coolant when I removed the head. Is there any other area I should further investigate whilst it’s stripped down before re-assembling with a new head gasket? I still pondering why the radiator burst so heavily.
Have you checked that your vent pipe is not blocked or crushed? I’ve had several head gasket failures and whilst I’ve seen the water being squirted out the overflow under pressure, it’s hard to imagine it blowing the radiator. See if you can blow down it.
Also your clean piston was likely steam cleaned by the engine sucking it into the cylinder. When I’ve had the beginnings of a failure whilst riding and not yet noticed, there was a lot of what looked to others like white smoke.. actually steam, coming out the exhaust.
It’s unlikely to have done any lasting damage… I flooded the mains with oil and put some in the bores whilst turning it over and took the doors off to do the same to the big end just to be sure.
As a note, my failures were down to a combination of some slight corrosion on my block face around a coolant hole and a slightly too narrow section of some composite head gaskets (between the bore and the coolant hole) where they didn’t seem to have punched out quite evenly. With the block face skimmed and a new gasket (I used one of my dad’s laser cut aluminium gaskets this time but another composite would have been fine) it has all been OK since.
I had a similar problem with my Brum. Turned out to be a blow hole in one of the combustion chambers. A new head was required as the ally was wafer thin in that chamber. I may get Alan Noakes put in some new inserts at a later date.
Aha !!! I wonder if that is the reason for my overheating/boiling problem ! The interior of the cylinder head appears to be OK,but if there is/are pinholes due to internal corrosion,this could be the problem. Question….is there a method of checking the head,once the head is off ??? Thankyou.
An interesting question…. I’ve just acquired a head, (unused old stock), that has the word ‘tested’ stamped on it, with an inverted 1 against it that I am assuming has been used as a tick, confirming a successful test. Presumably the head would have to be bolted down firmly onto a solid plate, water inlet/outlet plugged, and pressure applied via a connection in one of the plugs ?
I can thoroughly recommend having your combustion chambers replaced by Alan Noakes.
He did mine and a superb job to boot, profiling to the exact template provided – which even included a “pinch” around the edge of the combustion chamber as is modern practice.
And his charges are fair as your not paying for myth and rehetoric.
Thanks to all members who have posted advice & comments, how fortunate we are to be a club with so much help & experience on-tap, and so freely given!
Brian asked for an update once a full investigation had been made, so here are a few further lines:
I think it is pretty conclusive that the head gasket has been the source of the problem. In a parlous state when removed, soaked, delaminating & stained by coolant & leakage. Looks like it’s been progressive for some time. Thankfully everything else looks ok, piston, rings, bore passable (although some scoring to the latter right hand cylinder due to gudgeon pin/circlip – looks like a long-term injury so will leave as is). In the process of giving everything a good clean prior to reassembling. New gasket sets & seals already received from Graham, am also replacing the copper oil lines to tidy things up & waiting for red lacquer to refinish the block ditto. The poor old radiator was taken to a little unpossessing back street specialist in Hereford used to restoring rads for historic vehicles (located via google search). He was sceptical about taking on the job (wouldn’t consider re-coring) but after leak testing under pressure was willing to try a repair job. Phoned me the next day to say located two splits to tubing which he had soldered up & which remained air tight after retesting. Neat job virtually undetectable, two day turn around & cost £160 + vat. Time will tell how successful this will prove once under working conditions again. Will let you know at a later date. If all well, this may be a proven source for similar repairs of interest for other owners.
A few years ago I had a pseudo Sprint Special, ex-Derrick Shire, and it had a 596cc Hemmings Paramount 9-stud barrel and head, which had a reusable solid copper head gasket. I wonder if this might be a future thought for the Spares Scheme….
When fitting the new head gasket after the initial stud/nut tightening, you will probably find that after some time the nuts will require retightening ie following down, this may need doing several times and with the copper asbestos gasket can last for up to 6months before stability is reached.
And…. When tightening down the nuts always start in the middle and work your way outwards, going from side to side diagonally. Do not overtighten, best to do it gradually over a few months as suggested. ONE hand and a ring spanner, NOT a socket and long ratchet handle !