Spit 1500. Two cooling questions. Radiator and viscous coupling

[chrishawley]

Spit 1500 with some cooling problems. Cooling system overdue for general overhaul for sure, but there are two particular questions.

 

Q1. The vehicle has a non-standard rad. But I can't identify what it is. I think is from another Triumph of some sort. Could it be from a 1500? Any suggestions would be appreciated.

 

Q2. I'm none too sure that the viscous coupling is fully functional (excessive slip). It is difficult question, but how viscous should a VC be? Is there a handy way (before I take everything apart) to get a best guess on whether it's failing to provide sufficient fan rpm under hot condition?

As ever, all advice much appreciated.

[NonMember]

That looks like a Dolomite 1500 radiator but it's a long time since I owned one so I may be wrong. The header bottle is probably OK down there - the thing that matters is that the hose connecting it is at the highest point. It operates on a similar principle to the Spitfire system - as the coolant in the engine expands it expels air from the top of the radiator into the bottle, then as it cools it draws water back in. The only difference is that the bottle itself is pressurised so the air in the top of the bottle acts as a compressible expansion region.

You're not supposed to fill that type of system through the bottle, though. You're supposed to undo the hex-key headed plug in the top of the radiator. In-service top-up can be done through the bottle but only if it's not empty.

As to the viscous fan, the ones I've had were all pretty loose. You can tell whether it works by running the engine. If the fan spins at idle then it's sufficiently viscous.

[Pete Lewis]

most of these early viscous fans suffer bearing problems that give you a wobble or scream ,before the drive looses out,    the goo and paddle drive tends to work well 

what are the cooling problems you are experiencing ???

Pete

 

[chrishawley]

I 'll get another photo of the hoses as requested previously.

The symptoms are a gradual decline in cooling function over the past 4 or 5 years: initially getting somewhat hot after prolonged idling on hot days progressing to getting v.hot after short idling even under moderate ambient temperatures (and enough to cause poor running). In very other respect all is functioning normally. Apart from being topped up periodically the cooling system has had no attention since 1996.

I'll check the bearing on the VC. Thanks

[Pete Lewis]

have looked at changing the thermostat  ??

its  the main thing controlling temperatures   1500 is normally a 88C 

its the cheapest part to change 

have you removed or done the 2 x 1p mod to the waxstat jets ???

Pete

[NonMember]

1 hour ago, chrishawley said:

The symptoms are a gradual decline in cooling function over the past 4 or 5 years:

 

1 hour ago, chrishawley said:

Apart from being topped up periodically the cooling system has had no attention since 1996.

Might I suggest a good flush through and de-scaling is probably in order?

[Anglefire]

Rads in the spit 1500 were marginal at best when new.  I fitted a wide one from canley classics a year a so ago. Works well. 
and a fixed fan.  Viscous should work well but they can cause issues if they fail. 
 

[johny]

The fact that the car doesnt indicate hotter running when driving (for example up a long hill on a hot day) but only when idling would seem to indicate insufficient airflow from the fan as it does nothing once once youre moving. A flush is always a good idea on an old system and I would also clean the cooling fins as much as possible but it does point to an under performing fan....

[chrishawley]

Thank for the comments. V.helpful.

Must admit I'd never twigged that late 1500s had an 88˚ thermostat. So I guess that gives an option to drop that to 82˚ if need be.

Inspection of the viscous coupling has proved decisive. It's halfway hanging off it's bearing already so whatever the viscosityness is I need to replace that anyway. I note that VCs for MG Midgets are cheaper than 'Triumph' ones by quite a bit.

I do indeed have waxstats: Recently fitted genuine SU, NOS, ones and they seem to Actually Work! Is there anything extra I should be looking out for here?

So i guess that lines me up for a full cleanout and service of the cooling system. Still leaves me perplexed as to the identity of the mystery radiator (and I attach an extra photo of the 'out' hose). In practice, I suppose, it'll either scrub up ok or it won't and if the latter then there's plenty of options.

Assuming at least 25 years of accumulated crud I thought I might flush with washing soda. Would two cupfuls in a gallon of warm water be about right? And should I bypass the heater control valve or will it resist the hydroxide ok?

Thanks again

C

 

[NonMember]

Still looks like a Dolomite radiator to me, and the top and bottom hoses look like the ones shown in the Dolomite 1500 Haynes manual. It's a better cooling system than the Spitfire one - Dolomites don't generally overheat - so it's possible a PO did it as an upgrade.

[johny]

I think your probably right but I really would like to see the reservoir bottle mounted at the highest point in the system as surely it must have been in the Dolomite...

[Clive]

11 hours ago, chrishawley said:

Thank for the comments. V.helpful.

Must admit I'd never twigged that late 1500s had an 88˚ thermostat. So I guess that gives an option to drop that to 82˚ if need be.

Inspection of the viscous coupling has proved decisive. It's halfway hanging off it's bearing already so whatever the viscosityness is I need to replace that anyway. I note that VCs for MG Midgets are cheaper than 'Triumph' ones by quite a bit.

I do indeed have waxstats: Recently fitted genuine SU, NOS, ones and they seem to Actually Work! Is there anything extra I should be looking out for here?

So i guess that lines me up for a full cleanout and service of the cooling system. Still leaves me perplexed as to the identity of the mystery radiator (and I attach an extra photo of the 'out' hose). In practice, I suppose, it'll either scrub up ok or it won't and if the latter then there's plenty of options.

 

 

 

ars of accumulated crud I thought I might flush with washing soda. Would two cupfuls in a gallon of warm water be about right? And should I bypass the heater control valve or will it resist the hydroxide ok?

Thanks again

C

I think 88 is the winter stat, changed for 82 in the summer? Probably variations of where in the world you are too.

Washing soda does not contain hydroxide, but still attacks aluminium (at a much lower rate) so don't leave too long. Maybe just a cup in the system will be plenty, drive 50 miles and drain/flush/refill with antifreeze mix

My thoughts on viscous fans is that they are a good idea IF working correctly. But as they wear, they become a real risk to the radiator. If you can get a genuine replacement, that is worth a go, others=wise fit a std waterpump/fan. 

As to overheating, if a flush etc doesn't sort it, a new radiator may be required. Of course, this assumes you really are running hotter than expected, and not just a sensor or gauge over reading. 

 

 

8 minutes ago, NonMember said:

Still looks like a Dolomite radiator to me, and the top and bottom hoses look like the ones shown in the Dolomite 1500 Haynes manual. It's a better cooling system than the Spitfire one - Dolomites don't generally overheat - so it's possible a PO did it as an upgrade.

Deffo dolly radiator. It was on an old list of "parts that fit a spitfire if you have one lying around" so I expect that is a more likely reason. Spit rad holed, dolly one cheap/free and can fit. But if that much better, would have expected it to become a better know swap? 

Header tank position shouldn't make any difference. Air (and/or water) will be pushed out the rad as teh system heats up, and as it cools, only water should be pulled back into the rad. 

[johny]

Im not sure air will be pushed out to the reservoir because as the water expands on heating it will just be compressed the same as the air in the bottle. Theres no pressure difference between the bottle and system as there is with a standard 'open' arrangement so the expulsion of air just relies of floating to the highest point...

[PeteH]

Looking at the first Photo. I noted what appears to be a brass domestic radiator bleed valve in the top of the Rad?. If I am correct that would be the highest point, and the place to vent air just as you would a domestic radiator?.

Pete

[Clive]

52 minutes ago, johny said:

Im not sure air will be pushed out to the reservoir because as the water expands on heating it will just be compressed the same as the air in the bottle. Theres no pressure difference between the bottle and system as there is with a standard 'open' arrangement so the expulsion of air just relies of floating to the highest point...

The water in the reservoir "initially" does not heat up, so as the system water heats it expands, and will push a small volume out into the resevoir. As you note, the pressure will equalise quite fast. But that happening every heat cycle shoul dget most air out.

Much better would be a bottle with an added, larger (1/2" or 5/8) connect at the bottom, tapped into the bottom rad hose. As used on most cars from the 80s onwards. That continuously cycles water from the top of th erad (and often top of engine) through the expansion tank, keeping teh system free of air. I use them on my cars.

Pete, it is a plug, factory fitted, for filling the system. No idea of the thread size, but could be 3/4bsp? maybe bigger. Some have a hex recess, some are slotted. Some brass, some nylon.

[johny]

Yes luckily its got that plug as it should allow air to be vented but what a pain and each time you open it the coolant in the overflow pipe will run into the reservoir leaving the pipe empty...

Modern motorcycles still use the 'old' open system design precisely because there isnt room to mount a reservoir at the highest point. Its not as good as a closed type but is the best for that situation. 

[PeteH]

10 minutes ago, clive said:

Pete, it is a plug, factory fitted, for filling the system. No idea of the thread size, but could be 3/4bsp? maybe bigger. Some have a hex recess, some are slotted. Some brass, some nylon.

I would check the thread size, as If as it looks, it is 1/2" BSP or even 3/4". Fitting a domestic radiator bleed valve could be an option?

Pete

[Clive]

5 minutes ago, PeteH said:

I would check the thread size, as If as it looks, it is 1/2" BSP or even 3/4". Fitting a domestic radiator bleed valve could be an option?

Pete

No need, it is only to initially fill the system. the expansion tank does get most/all the air out, and is used for topping up if necessary.

[NonMember]

3 hours ago, johny said:

Im not sure air will be pushed out to the reservoir because as the water expands on heating it will just be compressed the same as the air in the bottle. Theres no pressure difference between the bottle and system as there is with a standard 'open' arrangement so the expulsion of air just relies of floating to the highest point...

Wrong. Water is incompressible but does expand with heating. Air is highly compressible. Unless you've neglected your system severely, the engine and radiator are mostly full of water, while the bottle is mostly full of air. Therefore, as the engine warms up, the water in the engine and radiator (which is at the bottom) pushes the air in the top of the radiator out into the bottle, as the larger air "bubble" is more easily compressed. As it cools, the pressure of the air in the bottle pushes the water in the bottom of the bottle back into the radiator. After a few such cycles, all the air is in the bottle.

3 hours ago, johny said:

I really would like to see the reservoir bottle mounted at the highest point in the system as surely it must have been in the Dolomite...

Actually it's on the inner wing on the Dolomite, with the pressure cap on the bottle just about level with the top of the radiator. Certainly not the highest point in the system.

[johny]

1 hour ago, NonMember said:

Actually it's on the inner wing on the Dolomite, with the pressure cap on the bottle just about level with the top of the radiator. Certainly not the highest point in the system.

The reservoir the same height as the radiator makes more sense because I reckon with the existing arrangement you could have a substantially low level in the radiator and not know it because the reservoir still has coolant. The only way to be sure would be to remove the plug....

[Clive]

In that situation, the coolant should suck the contents of the tank into the rad as it all cools down. 

[johny]

Thats what the normal open system would do but I think with sufficient air in the rad the water expansion would be absorbed without air being expelled. After all theres got to be some reason why car manufacturers mount pressurised reservoirs high up... 

[NonMember]

29 minutes ago, johny said:

theres got to be some reason why car manufacturers mount pressurised reservoirs high up

Yes, but it's not relevant here. The reason is that modern cooling systems use a completely different type of "presurised reservoir" which has continual water circulation through it. That type MUST be the highest point. The Dolomite type doesn't need to be and never was.

[johny]

Well either way it certainly isnt helpful trying to diagnose and correct problems on a cooling system when starting with a non standard set up😌

[chrishawley]

From the suggestions above it does look rather like this radiator setup is actually a transplant from a Dolomite 1300. Not that that solves anything as such since I've still got to replace the fan coupling and service the system; but it does open the question of whether this is 'a bodge' to be got rid of or an 'authentic period modification' to be cherished for its idiosyncrasy. Hmmm. Descions, descisions!