Club Triumph

No, the subject is not a misprint, I have never had an overheating problem with my 4A and in the colder weather struggle with the opposite problem -- I can't get the engine hot enough in normal running. I have never had a radiator duct fitted, have no mechanical fan and rely on  a Kenlowe fitted in front of the rad. for cooling. This only ever cuts in when the vehicle is stuck in traffic for an extended period at slow speeds or when climbing in lower gears at higher revs in high ambient temperatures. I run a 92 degree C wax stat type thermostat all year round with a 50/50 mix of distilled water and ethylene glycol based anti-freeze and in colder weather as at present I have the lowest four inches of the radiator blanked off.  On a trip up the A1/A14 on Saturday the temperature gauge never rose above 3/8. Many years ago I obtained an original bellows type AC thermostat at an autojumble.  This has a sleeve which progressively closes off the bypass outlet from the stat housing as the stat opens and it is rated at 86 degs C. I eventually found this stat in  my junk store and tried it yesterday, the gauge would not get above 1/4 when running under similar conditions to Saturday. I guess this was predictable since if the bypass is cut off then more water goes through the rad for more cooling. I tested the 92 degs thermostat in a saucepan and found that it started to open at an indicated 91 degs., so no problem there.
I could of course solve the problem by blanking off more of the radiator but then if the temperature rises when the car is stuck in traffic the Kenlowe would be rendered useless and the engine would overheat. I think the ideal solution would be a radiator blind adjustable from the driver's seat but unfortunately these went out with the ark. Has anyone any other ideas/suggestions please?

Tim

Hi Tim,
             if you wanted a roller blind for the rad then why not try somewhere like B&Q in their curtain dept.
I'm sure that blinds are available for narrow/small windows or in kit form.

I've often fancied making a Rolls Royce style thermostatic rad blind with chromed slats.

Roger

Thanks Roger, I'll see what they have. I've got about 3/4" clearance between the pushing Kenlowe fan and the rad (it's an old kit, not the newer type that actually fixes to the core) so a roller blind might just fit.

Tim

Hi Tim,

That sounds like a good problem to have, my temperature guage tends to spend most of it's time with the needle in the top half!
Silly question, but I suppose you have checked that the gauge is reading correctly?

Keith

When ever I've had this problem on old Triumphs or anything else it has always been down to the thermostat in the end, saucepan testing notwithstanding.  

Nick

Thanks Keith and Nick. I am sure the thermostats are OK. I have also tried a 91 deg C stat and this is no better in the car. I have no reason to doubt the temperature gauge, it will happily go above half way when the car idles for a long time whilst stationary until the Kenlowe cuts in at something over 3/4, still below the red sector. I didn't mention that I do have an oil cooler fitted which is also removing heat from the engine and the block is very clean so cooling efficient. The car behaves perfectly in the warmer weather, say with ambients above 15 deg C and in summer I can even dispense with the four inches of rad blanking. in winter however I really struggle to get the engine warm. I much prefer to see the temp needle above half way. This is more efficient and will cause less wear I am sure.

Tim

Very strange that the thermostat is not managing to get the coolant in the engine up to the correct temperature.
Is there any way the coolant could be by-passing the thermostat, in sufficient volume, to cause this?
Is the top hose getting hot, properly hot?
Is there much water entering the top of the radiator when engine coolant temperature is as high as it
goes?

Blanking the radiator will only help if coolant, that should mostly be being held in the engine jacket by the thermostat, is actually circulating through the radiator at a fair volume.

You've got the same issue as me, except mine is because my radiator is too big. ;) In winter I used to blank off over half of it as without doing this the needle didn't move. No matter which thermostat sits in the engine it behaves the same way. Start it up on the driveway after washing the engine down or in damp air and the radiator will steam after a few minutes, so it's all working! If in traffic the gauge climbs to half way and sits there.

The important point not stated - is the car heater putting out hot air? If it is then I'd not worry and put it down to the gauge, they're only an indicator after all and not a thermometer which makes every scale different. Has the radiator been re-cored? If it has it's possible it's now a super-duper efficient one for some reason.

My theory goes that as the thermostat opens it allows the extremely well cooled water in the radiator to leak into the engine block which cools the existing water into the system to cool quickly. The thermostat shuts as a result then slowly the cycle happens over and over. The gauge doesn't react fast enough to show it happening.

is the oil cooler thermostatically controlled?  If not, there may be the root of your problem?

If the thermostat is working correctly, radiator size should be irrelevent as the thermostat will keep it out of circuit unless needed.

Ignoring that, we are left with Mikes suggestion that the oil cooler is part of the problem and, if it is not thermostatically controlled, that could well be true.  Also could be true that your particular temp gauge/sensor combination shows a relatively large amount of movement for a relatively small temperature change which makes things seems worse than they actually are.

Nick

Thanks all for additional thoughts. Yes I do have a thermostat in circuit with the oil cooler and recently checked that it is operating correctly, quite impressive really, it's over 32 years old!

Tim

I had an issue years ago with the Temp Gauge showing inaccurate readings?

Mechanical temp gauges are one of the first things I now fit to a Triumph car.