And yet there are people who don’t believe Tefba filters are worthwhile.
Hotter temperatures might make things worse. I live in the country and have well water that’s pretty hard. The bottom of my electric water heater gradually fills up with hard chunks of what looks like rocks. The water is only heated to perhaps 125F, but the water right against the heating elements can be heated to near boiling; you can hear the water heater make sounds when that happens, interesting because there are no moving parts. Anyhow, this heating causes the minerals to form deposits right on the heating coils. Once these deposits get big and thick enough, the thermal shock from the elements turning on and off cracks them and they fall to the bottom in chunks. This keeps going until the water heater fills to the point where the lower element is surrounded by chunks, and then that element burns out.
The fix for this is what is called a “low watt density” heating element. Rather than a simple loop, these heating elements are double loops but still the same wattage. So they have about twice the surface area for the same wattage. The water right next to the surface doesn’t get as hot, the water heater makes less sound, chunks don’t accumulate in the bottom so fast (although they still do), and when the lower element is surrounded by debris it has less tendency to burn up.
It’s my contention that the hot surfaces inside the cooling jacket form deposits in exactly the same way if hard water is used to fill the cooling circuit. That means the outside surface of the liners and I presume the hidden inside surface inside the heads surrounding the valve seats and combustion chamber. And it’s probably a good theory that pknellie’s track work got something in there hotter than it’s seen in a while, hot enough to crack some of those deposits loose.
All of us who have had heads off have seen the stuff surrounding the liners, especially at the rear. How many of us have seen what’s going on inside the cooling passages in the heads? Perhaps such deposits form on the surface surrounding the combustion chamber, and if the car is never subjected to track days or the occasional Italian Tune-Up these deposits get thicker and thicker until they effectively insulate the combustion chamber from the coolant. Which, in turn, allows the valve seats to overheat and drop, even if the coolant is flowing just fine through the heads.
What’s more, perhaps this is part of how an Italian Tune-Up works. Besides “blowing out the carbon”, perhaps it also breaks deposits loose in the cooling jacket. That would certainly help explain why it cures a pesky engine knock.
as usual i take a different approach:
when i was rebuilding my heads ( i do everything myself ,sorry Ego problems).
i set both stripped heads out back on wood saw horses, fill the cooling jackets with raw MURIATIC ACID, let them foam and boil the inner castings, all kinds of crap comes out, then run a garden water hose into many holes till it runs clear , then mix some Sodium Bicarbnate solution pour it in let set then flush again with water!
it also increases more inner surface area to the coolant!
the V12 block is easy to clean once all liners are removed, scrub with a small metal brush, hose it off ,and start examination for anything else!
ron
Would toilet bowl cleaner work?
Or CLR? 
I had one eye checking the dash gauges periodically and she didn’t get above 85c until after the sprints. But I suspect that these readings would reflect a delayed average and that at the end of the straights there would have been some focal temps around the heads I wouldn’t want to know about.
I live in the bush and our toilet uses ground water. The porcelain gets a orange clay stain after a few years that nothing will shift… not even 1200 wet n dry. Until I tried 10% diluted HCl… wiped off like white board marker.
So maybe it’s like Ronbos says… acid then neutralise with alkaline.
I hope you are all drinking bottled water or something that has been distilled, or fermented, and filtered.
2 Likes
I’m not talking about coolant temperature, I’m talking about metal temperature. The iron of the liners and the aluminum of the combustion chamber presumably gets a LOT hotter when thrashing it than when puttering around town.
Unfortunately, I’ve never found CLR to work on anything.
Agreed: it’s garbage.
When I need to remove the hard water stains of my hard well water, I use dilute muriatic acid.
Further observations.
I took Roxanne for a drive this morning to see how she felt after her post sprint purge and filter clean out and observed what I didn’t expect.
Her running temp at last Saturday at 5 am on the way to the track was normal at around A=82C and B=84C with the temp gauge about the middle to upper N (Pic 1)…. the morning temp was 3degC.
However this morning she is running at A=78C and B=81C on the same road and same speed but the day is 9degC… 6 degrees warmer.
While we can explain this with the purge… ie water flowing more freely, the position of the needle on the N surprised me (Pic 2). I have never had her running up to temp and had the needle so low.
We all know that this difference in the digital temp read outs would not make this much difference on the analogue gauge, so what is doing this? Could it be that as the analogue temp gauge sensor is on the A side water rail and the majority of the purge was found in the A side filter… the purge came from a compromised water rail or flow for same?? And now it’s getting a more normal flow?
I will leave it to those more savvy with XJS coolant hydrodynamics to comment on this.
Trev
PS a lot to be said for the Italian tune up.
You gave it one hell of an Italian Tune-Up!
In my limited experience, your barrel gauge readings are not what I’d expect for temps in the 78-84C range. I would have expected your needle to sit a ways below the N, closer to halfway between C and N. You normally need to install 90C thermostats to get the needle up to where your “post purge” photo shows, and getting to where the “pre purge” photo shows would be cause for worry.
Of course, barrel gauges are not the acme of accuracy – as you know as well as anyone. Still, I’d be thinking about what sort of electrical fault can cause that gauge to read high.
Well, good old white vinegar is famous for dissolving mineral deposits… and it really works.
I was wondering if there would be any ill effects if one just added a liter or two in the cooling system and left them there… ok, maybe not for ever but for some time until deposits dissolve… maybe…?
Aristides
Don’t do that without the coolant filters in place!
I might put a drop or two on some my recovered crud and see…
I took one of the larger chunks of crud and subjected it to a very basic hardness test compared to a grain silica.
Placing the samples between two pieces of iron plate a squeezed between my fingers. The crud disintegrated with little pressure and the silica remained relatively unscathed with even a great deal more pressure… there is indeed more to this crud than silica. Also I note that the larger granules of crud have become more opaque the longer they are in air = drying out = not silica.
See if you can figure out what will dissolve it.
Pro tip: what dissolves silica is high (alkaline) pH.
SiO2 is mobile in hot liquids of pH 11, or greater.
I currently have a course grain of known silica in a jar long side a small pile of XJS coolant crud. To this I have added 50% vinegar/demineralised water.
Not the typical violent alkaline/acid reaction one might expect but rather a few small bubbles appeared after a while. The whitish dust in the crud has disappeared but the silica type crud granules have assumed their previous various coloured status but otherwise not changed. The control grain of sand has not changed.
It is under timed photography so I will post the outcome after 24 hours.
Trev