Descaling a Sprint radiator

[GrahamFountain]

I've got some concerns that the radiator isn't cooling as well as it should, though it's only in the hot weather that it gets really worrying, and only when in very slow traffic. I've flushed it with Wynns rad flush, and that's not made any big difference - as the weather is getting cooler, it's getting less of an issue anyway.

It was re-cored in May last year, and I've been back to the firm that did it to ask about possible upgrades, etc. They've suggested I first put two dishwasher tabs in for a couple of days, to fully descale the system. But I'm concerned about the caustic soda acting as an electrolyte between the alloy head and block.

So I just wondered if anybody had tried this, what effect they saw, and what alternatives anyone might suggest?

Graham

[SprintMWU773V]

Have you checked your VS output? If that's wrong then no amount of descaling will make any difference. I don't think you'll do any harm with the dishwasher tablets but I can't see this doing any better a job than the proper rad flush.

[GrahamFountain]

What's the "VS output"?

[Magenta Auto Sprint]

25 years ago my 1942 Jeep was over heating, so i went to replace the thermostat only to find there wasn't one fitted. So I used Holts rad flush, I left it in for a month as as I drove round I could see the temperature gradually reducing, when the temp barley got above 50C I flushed it through and fitted a thermostat.

Malcolm

[Toledo Man]

What's the "VS output"?

Mark is referring the the voltage stabilizer which provides an accurate reading for the fuel and temperature gauges. It is located on the bulkhead above the fusebox.

[Aleco]

I've used cheap Vinegar with good results. I filled the radiator and left it for a few days.

[SprintMWU773V]

Sorry yes he's right. The voltage output measured should be 10.2v or near as damn it from memory. If for example you get 12v then your gauges will massively over read, under then they will under read.

You'll need a multimeter to test the output, easy job. If it's an original type, and it probably is then I can pretty much guarantee that it will not be giving an accurate output. There's no point in doing loads of unnecessary work when actually it's just a faulty component. My Sprint used to give a high reading. I needed a new rad anyway but the real difference came when I changed the VS.

[GrahamFountain]

Okay, no, I've not checked the stabilizer. But I've checked the temperatures with an IR thermometer, and it's definitely running a bit hot. There was another thread on this before, but I thought the specific question about dishwasher tabs warranted a new one. The rad inlet temp is about 98C and outlet's about 90C with the 80 Watt fan on. That's after being left to idle for about 20 mins, the fan coming on from full cold in about 10. The last time I tested, the fan would not go off with the car stationary at an ambient temp of about 22-23C, though it had done before I did the pump, when the air temp was a little lower. It does go off after about a minute at 30, and only comes on when stopped or moving slowly in traffic. I hope to do that test again tomorrow – Saturday being the only day I don't have to drive it first thing.

The reason I worry about using dishwasher tabs is that there's a widely repeated recommendation not to let aluminium touch steel in the dishwasher, and I had an old Boot's Sabatier with a s##t metal (zinc-aluminium alloy) ferrule attached to the blade that dissolved over a few years.

[MIG Wielder]

Dishwasher tablets are highly alkaline, so they will have no effect on limescale.
Radflush is the stuff to use as it will be a developed product by the manufacturer. Don't forget to use the part 2 can of neutraliser after the main treatment.
Tony.

[Magenta Auto Sprint]

Holts rad flush contains the following active incrediants
Ethanol 1-5%
SOLVENT NAPHTHA <1%
SODIUM HYDRO <1%
PHOSPHORIC ACID <1%
METHANOL <1%
DIETHANOLAMINE <1%

Not very strong but may be worth leaving it in longer, all dishwasher tablets have an acidic content as well, some worse than others.

malcolm

[longboarder]

Central heating cleanser, X400. Brilliant stuff leave it in, drive around a while then flush it while hot. Amazing what is suspended in it.

[Galileo]

Most dishwasher tablets are salts, even more de-greasers, a load of protein converters with a sprinkling of perfume and a little citric acid. You can get citric acid cheaply in Boots (mix with sodium metabisulphite for a great disinfectant) and put that in as put in a dishwasher tablet, but as has been said, you would need to neutralise that acid to stop galvanic corrosion afterwards; that's probably why the Holts heavy duty Radflush comes in two bottles.

[MIG Wielder]

Radflush have an H & S data sheet on ingredients here.

http://www.partinfo.co.uk/files/RK3R%20 ... 20MSDS.pdf

Summary : Part 1 is 10 to 30% citric acid. That makes sense for limescale.
Part 2 is Sodium Silicate. Not sure what that does. Any chemists on here ?

The ethanol / methanol listings may help with oil residues but not limescale.
Tony.

[misterp]

I used white vinegar...cheap as chips and leave it in for a few weeks then flush.
If you need to do another flush it costs next to nothing to pop down to Tesco's and get some more.

Saying that however....if the rad it blocked, then no amount of flushing will fix it. Its WELL worth dropping to a rad specialist and they can rod it to clean any blocked tubes and give it a general service and paint.
Surely though...the cost of the replacement/alternative radiators from Saabs and Vectras and the like is so low (especially over there in the UK) that wouldnt it be worth just getting a new one for peace of mind?

[Galileo]

The sodium silicate might serve a few purposes other than as the assumed neutraliser of the citric acid, seems it's a sealer:

"Liquid glass" (sodium silicate) is added to the system through the radiator, and allowed to circulate. Sodium silicate is suspended in the coolant until it reaches the cylinder head. At 100–105°C, sodium silicate loses water molecules to form a glass seal with a remelt temperature above 810°C.

A sodium silicate repair can last two years or longer. The repair occurs rapidly, and symptoms disappear instantly. This repair only works when the sodium silicate reaches its "conversion" temperature at 100–105°C. Contamination of engine oil is a serious possibility in situations in which a coolant-to-oil leak is present. Sodium silicate (glass particulate) contamination of lubricants is detrimental to their function.

It also has clumping properties when there are fine particles in water, as well as being the key ingredient of exhaust sealer/lubricant paste!

The alternative rads such as the typical SAAB one do need some bodywork alterations though don't they? I think this might put people off, it does me, I don't mind reversible mods but I balk at doing any hacking about.