Losing Water

[thirdangle]

Hope you can help. I've got a TR4 running on the original style belt driven radiator fan. Last winter I had the radiator (extended filler neck type) reconditioned. All re-fitted & seemed fine although only ran it a few times over the winter, maybe 50 miles or so. Having used the old girl a few times over the weekend I notice that the rad has lost a lot of water. Managed to isolate the problem to water escaping down the overflow tube when the engine has been switched off after a run - it seems to discharge a small puddle & then stop. The only other thing of note is that when refitting the recon rad I fitted a new 7 psi rad cap (same rating as the original), but I had noticed that the large flat rubber gasket on the underside of the cap seems to get quite stuck to the top of the filler neck & needs to be peeled away, & re-seated in the cap.

 

I'm wondering if the cap is faulty or if maybe I have a airlock (if so, how do I clear it), or is there maybe another explanation? Incidentally, the temp gauge shows nothing abnormal so I'm guessing that the rad itself is ok, or maybe not?

 

All help would be appreciated

Edited May 6, 2008 by thirdangle

[BrianC]

This type of radiator will pump water out after warming-up if you overfill it. When the system is cold, only fill it to just cover the bottom of the filler neck extension (about 1/4"). If it has been overfilled, provided everything else is in order, you should find that, after it has pumped out the excess and cooled down, the level is just as described above.

 

The other well-known pitfall is to fit the wrong radiator cap - there are two 7lb caps. You need the 1" deep cap (Moss GRC102), NOT the 3/4" cap (Moss GRC112) which is for the later rad with no filler neck.

[davidgsmith]

I have just changed my rad for an uprated version (from an enterprising TR company) which has no filler neck, unlike my old one. Is it necessary to change the cap too as I am using the same cap I was on the long-neck rad?

Thanks

[Tr4Tony]

Yes ... you must have a 7lb cap minimum, whatever the rad.

 

The water in the rad needs to just cover the top of the bars of the rad inside - this allows enough space for the water to expand and contract without vanishing down the overflow pipe into the bottle. Dont overfill, or youll just lose it.

 

Also make sure that you dont have an air lock in the system ....

 

Regards

 

Tony

[davidgsmith]

the cap i use now is a 7lb anyway. not sure if it is 1" deep or 3/4", so i don't need to change it then?

[thirdangle]

the cap i use now is a 7lb anyway. not sure if it is 1" deep or 3/4", so i don't need to change it then?

 

No neck = 3/4"

Neck = 1"

 

Can anyone suggest a simple way to remove an airlock? Looking at the piping, it seems designed to have no obvious high point air traps, so not sure where an airlock could be>

[davidgsmith]

The thing I have done in the past is make sure that the heater tap is open so you have hot air in the cabin. As the tap is the highest point on the system, carefully undo the hose clip on the tap and and with your arm suitably protected from potential scalding water with a thick rag, gently pull the hose back until you see water seeping out. That way, you should get rid of any airlocks and you should have hot air blowing in the cabin.

Hope this helps

Edited May 7, 2008 by davidgsmith

[thirdangle]

The thing I have done in the past is make sure that the heater tap is open so you have hot air in the cabin. As the tap is the highest point on the system, carefully undo the hose clip on the tap and and with your arm suitably protected from potential scalding water with a thick rag, gently pull the hose back until you see water seeping out. That way, you should get rid of any airlocks and you should have hot air blowing in the cabin.

Hope this helps

 

Thanks David - And I always thought the heater fan switch just activated the 'play button' on the radio cassette which started a tape of a recorded humming noise, because I've never felt any hot air!!!!!

[BrianC]

I have just changed my rad for an uprated version (from an enterprising TR company) which has no filler neck, unlike my old one. Is it necessary to change the cap too as I am using the same cap I was on the long-neck rad?

 

Yes ... you must have a 7lb cap minimum, whatever the rad.

 

I believe all the 'filler-neck' radiators fitted to TR2-4 originally used a 4lb cap, and that the 7lb cap was used when the 'no-loss/sealed' system with overflow bottle was introduced, although I'm not sure that this coincided with the introduction of the 'no-neck' radiator. I don't know whether the increase in pressure is possible simply by converting to a 'no-loss/sealed' system by fitting an overflow bottle, or if the pressure is limited by the design/construction of the earlier 'filler-neck' radiator. Apart from a higher boiling-point, is there any advantage in having a higher pressure system?

 

 

I always thought the heater fan switch just activated the 'play button' on the radio cassette which started a tape of a recorded humming noise, because I've never felt any hot air!!!!!

Despite the poor reputation of the Smith's 'fug-stirrer', I was pleasantly surprised to find that the one in my TR3A actually performs quite well since the rebuild. I assume this is due to the thorough cleaning of the engine waterways and replacement of all hoses, as the heater matrix just had a quick back-flush with a hose pipe and check for leaks. I just wish I had put new bearings in the motor as it does sqeak and rattle, but I had forgotten about that during the car's 20 years hibernation,

[davidgsmith]

i will go to moss tomorrow and check which cap i have already. do we think it is necessary to have the particular 7lb cap?

[littlejim]

The 4A with the overflow bottle, requires a different 7lb cap to let the water suck (get pushed) back into the radiator. Forget the terminology used to describe the cap's ability to let the water back into the radiator from the bottle. (That's a long while back and I've had to learn so many new words about the 4a that that one's disappeared.)

Edited May 8, 2008 by littlejim

[davidgsmith]

so probably no reason to change my existing cap then as i dont have an overflow bottle ??

[thirdangle]

Thanks to all for your contributions. It seems the 7 lb extended filler neck type cap has solved the problem