Descaling a Sprint radiator

[sprint95m]

The alternative rads such as the typical SAAB one do need some bodywork alterations though don't they?

No.
It even mounts onto existing fixings (for the front bumper).
The hoses need to be constructed but this is easy enough using standard silicone components.




Ian.

[sprint95m]

It was re-cored in May last year

Just over a year ago?

There is something very wrong if it needs to be descaled already.




Ian.

[Galileo]

The alternative rads such as the typical SAAB one do need some bodywork alterations though don't they?

No.
It even mounts onto existing fixings (for the front bumper).
The hoses need to be constructed but this is easy enough using standard silicone components.

Ian.

Good to hear, that option might be on the cards then for next summer as my Sprint's cooling is very much borderline in hot weather. On some of the 25c+ days we had the temperature sat quite hot at motorway speeds, and struggled to maintain at idle.

[GrahamFountain]

I just re-ran the test of the time it takes for the fan to come on from cold and it took the same 10 minutes as before, and the fan still does not go off at idle. The interesting bit about that is that the first test was done at about 22-23C ambient, and this one at 11-12C. That it's not longer, at a lower ambient, adds to my belief that the problem lies with the rad – there' reason to think the pump is working well enough and the fan switch is about right at 90C on and 80C off.

That the time is no different despite the lower ambient, also suggests to me that the Wynns rad flush did little to nothing.

I'm thinking of doing the same test again with the heater turned up and its fan on full, to see if that lengthens the time, but I wouldn't know how to analyse the effects.

On the point that the rad was only re-cored in May 2015 and shouldn't be scaled yet: it shouldn't. But I've swapped the engine since then with one that had been stood, so I was a bit concerned there could have been crap in the galleries. Also, it had a leaky water-pump, and I was topping it up for a couple of months with tap water till I could get a round tueit. The water's not that hard here - I used to live in Hull, and that water's "well hard" (I so love a bad pun), but there could have been/be some scaling from that.

The rad may not have been working stunningly well with the old engine from new, but the old engine had other problems, and I never got around to measuring how well/poor the cooling system was before I had to replace it.

So I think it's either a poor rad core (not enough fins or galleries) or there's some other problem I haven't thought of and eliminated, like poor pump effort, blockage, or air-lock (all of which I think it's not). The place that did the re-core appears to be a proper engineering place that specializes in thermal management systems, and only over in Preston, so I may be able to take the car to them and have them see if they can pinpoint the cause. But, now the summer is clearly over, it's not a big rush.

Graham

[Galileo]

I was doing some reading* on this the other day, idly wondering if Triumph got the cooling system figures wrong (having a Cambridge Uni ID helps and I know, odd thing to be doing but I am odd!). The difference between the top and bottom of the radiator on average should be around 3-8°C, the exact figure depending on water inlet and air temperature. This will not alter no matter how big the radiator is, what will change is the volume of water that can be cooled, the same when it comes to flowrate as there is a maximum when increasing the flow will have no temperature dropping effect.

"Typical coolant flow rates are 1.3 to 2.5 L/min per kW of brake power"

"The water velocity in the radiator must be below the saturation range, which is defined as that velocity beyond which there is little or no increase in heat transfer. A water flow rate of 1.4 kg/min per radiator tube is generally below the saturation range."

"The liquid temperature entering the radiator is 98°C. The ambient air temperature is shown as 40°C, i.e., a hot day is assumed for a conservative design. If the drop in coolant temperature, ∆Tw, is 8°C and the rise in air temperature, ∆Ta, is 15°C, then the heat transfer difference, ∆Tr, will be 35°C."


*Off-road Vehicle Engineering Principles - Carroll E Goering, David W. Smith, Marvin L. Stone, and Paul K. Turnquist
Engines: An Introduction - John L. Lumley

[AlanH]

Tony Hart does the Supergill radiator for Stags. I'm sure that I heard somewhere he has done them for Dolomites also.

This seems very strange, do you use tap water?

[sprint95m]

I was doing some reading* on this the other day, idly wondering if Triumph got the cooling system figures wrong

They didn't get their figures wrong because if they had then no car would run at the correct temperature!

They did however go wrong with the "expansion tank" system because it permits a situation where the level can drop within the engine but not the tank.
This is easily cured by using a proper header tank.

Further, the water pump design is poor leading to a hot spot at the back of the cylinder head. Again this can be overcome using more recent technology,
that is by the use of Evans Waterless Coolant, because unlike a water based coolant, EWC stays in contact with all surfaces constantly,
thereby removing the pump's tendency to cause cavitation (and the resulting hot spot).
Alternatively an electric water pump can be employed, however to plumb one in properly involves reworking the car's plumbing a lot. A Stewart EMP pump
flows at 200 litres/minute and is guaranteed for 10,000 hours. Unfortunately these are not sold in Europe so have to be imported from the USA. The performance record
of they pumps speaks for itself.


With regard to Graham's overheating problem, I feel a more systematic practical approach is required.
The cooling system needs to be pressure tested first. The ambient temperature doesn't matter for this test.



Ian.

[GrahamFountain]

What will a pressure test show?

Graham

[Galileo]

They didn't get their figures wrong because if they had then no car would run at the correct temperature!

Do they though? I was a bit young to be driving in 1973, so did a brand new Sprint back then with an ambient temperature of 28°C at say a constant speed of 120kph for an hour stay at the same normal temperature as say if the ambient air temperature was 15°C? If they did get their sums right, did they allow for any extra margin for wear and tear on the cooling system and exceptionally hot days or long fast runs? These were the questions I was asking myself, and it coincided with Graham's post about his radiator, and as he has a non-contact temperature gun he can easily check the temperature differential to test his radiator is within a known documented automotive specification.

[sprint95m]

What will a pressure test show?

It will check the cooling system to see if it has any exhaust gases present (head gasket failure).



Also,
Do you still have an original type expansion tank? These are the weakest link of the cooling system,
mainly because the caps don't always seal properly, thereby preventing water based coolant from reaching
its required operating pressure…..resulting in overheating.




Ian.

[sprint95m]

They didn't get their figures wrong because if they had then no car would run at the correct temperature!

Do they though? I was a bit young to be driving in 1973, so did a brand new Sprint back then with an ambient temperature of 28°C at say a constant speed of 120kph for an hour stay at the same normal temperature as say if the ambient air temperature was 15°C? If they did get their sums right, did they allow for any extra margin for wear and tear on the cooling system and exceptionally hot days or long fast runs? These were the questions I was asking myself, and it coincided with Graham's post about his radiator, and as he has a non-contact temperature gun he can easily check the temperature differential to test his radiator is within a known documented automotive specification.

Triumph did have a testing regime,
however they still went and burdened Dolomites with they so called expansion tanks .


Ian.

[marko]

Any help towards the alternative to the Dolomite expansion tank? My 1500tc has the expansion coming from the top of the radiator, would it be better from the thermostat housing?

[GTS290N]

The Stag also suffered from cooling problems, but if the car had been produced properly the cooling was sufficient for the engine. The problems were poor quality control, the actual cooling design was perfectly sufficient, as demonstrated on some TV programme - can't remember which one.

[Galileo]

The Stag also suffered from cooling problems, but if the car had been produced properly the cooling was sufficient for the engine. The problems were poor quality control, the actual cooling design was perfectly sufficient, as demonstrated on some TV programme - can't remember which one.

For the Love of Cars Episode 4

[GTS290N]

Thanks for the link. I've justed wasted 20 minutes watching Stag related clips. I've got more serious stuff to do!
Toddles off to watch some hockey of the ice variety..