Water Temp problem

[stuartgb100]

I like to run my Sprint on the cool side, so I have a 72 deg C (161.5 F) thermostat fitted. I also have a Kenlowe fan, thermostatically set to cut in at 87.5 deg C (190 F), although I may well lower this setting in the future.

I had thought the temperature cycle went something like this:

Start the car (thermostat closed); engine and water warm up, etc;
at or about 161 deg F the thermostat opens; car cruises at this temp.

This is in fact what does happen on the open road ....... except for when in traffic, or stationary etc, when the temperature rises and the fan kicks in.

So, for the past 3 years I thought all was tickety-boo.

Took the car up to Stoneleigh today, and was poodling along at 60/70 (+)
when I glanced at the temp guage ....... it was reading 180 !!

So I decided to watch the guage carefully, and this is what I found:

The 'normal' running temp is 162-165 deg F.
After 15 seconds or so, the temp will climb to 185 deg F (takes 5-10 secs)
then drops back to 162-165 deg F.
It will repeat this cycle something like 3 times a minute.

It repeated this behaviour for the rest of the trip.

Back in the garage, inspection reveals little ....... except a hint of very minor coolant weeps from the top hose/thermostat housing conection, and the thermostat housing/heater connection.

There is no obvious loss of coolant from the rad.

Any ideas what is going on ?

I can only think that there may be a loss of pressure.

Regards,
Stuart.

[oldokie]

In my case the thermostat was getting a bit sticky, constantly opening and closing. I had it in a pan on the stove and watched it to make sure, it would open, take it off the fire, it would close right up again, no 'range' to it at all!

[bcmc33]

Stuart,

Repeat the exercise without the thermostat ? if you want your engine to run cool, then maybe you don?t need one.

I always thought my engine ran hot with the fan coming on in very slow traffic conditions. To address this I got a nice full width radiator from a regular seller on fleabay ? without the filler cap, fitted a Ford thermostat/filler housing with an 82 deg C thermostat from Burton, plus a new 92 deg C fan switch that fits in the housing.

The only disadvantage with this set-up is the need for an elbow in the top hose. You could buy Cliveyboy?s housing for 75 quid that will use the standard hose, but I chose the Burton 16 quid housing and made-up an elbow hose.

The car now runs quite cool, but I must admit there has been no really hot days this year to give it a real test. The only obvious difference that I can detect is that the fan does not come on anymore when the engine is switched off after a decent run ? the fan in the original system always ran for 5 minutes after the engine was turned off.

From an engineering point of view, there is some satisfaction in knowing that the filling point is now at the highest water point of the system.

O?h by the way, I added Water-Wetter ? maybe that was the real secret of success.


Brian Clarke
(1972 Sprint)

[pamitchell]

What is the best psi for the rad cap to help with cooling?
TIA
Phil

[JJDraper]

It might be worth having a look at your thermostat. I understand from PM's guys that original thermostats had a small hole in them so that even when fully closed, there was a slight flow through. This helps prevent the 'hunting' effect such as you describe. They suggested drilling a small (3/16th) hole in the diaphragm in the modern thermostat, which doesn't have one.

Works for me.

Jeremy

PS congratulations Swampy, (Silver +2), you made me realise that brilliant paintwork isn't everything!

[steveww]

I always drill a small (3mm) hole in the thermostat flange. As already stated this helps with the hunting and also helps getting rid of air locks. Buy a new thermostat and drill the 3mm hole and your problem will be solved.

I fit a summer (IIRC 74C) one. The engine runs at this temp once warmed up. It only goes above this when stationary or in very hot weather, typically in France

[hatman]

Also beware of deceitful temperature gauges. What they indicate ain't necessarily the same as the actual temperature of your coolant.

My recently refurbished gauge is now reading a good ten degrees higher throughout the range, to the extent that, on a recent drive, I was horrified to see it indicating a running temp of between 100 and 110, occasionally higher. After putting the heater on full blow and cruising steadily back home, all to little effect on the gauge and all the while expecting a geyser of steam and boiling water from the rad, I was surprised (and relieved) on reaching home and checking the overflow bottle and pipe to find that they weren't even warm, proving that, even at the hottest part of the drive (a heady 112 ish indicated on the gauge) actual coolant temperature was still within the 'normal' range (probably no higher than 95/100 ish).

Wasn't totally surprised however as I had a similar experience with a Rover V8 that I ran for millennia, where the factory fitted set up showed the car to be running consistently lower than the green 'normal' temperature but, on replacing the sender when it finally died the needle then took up permanent residence bang in the middle of the green sector.

[stuartgb100]

Hi all,

Many thanks for the replies.

I had forgotten about that little hole ! but am suspicious of the thermostat.

Will try a new one at the weekend.

Regards and thanks again,
Stuart.

[bcmc33]

Stuart,

Sorry, I forgot to mention the trick of a 3mm hole in the thermostat as this is a method of treating the symptom and not the root cause of the problem by making sure that there is a constant trickle of water running down the empty top hose.
The original thermostats had a hole to overcome a design shortcoming (failure in today?s terms) of not having the system full of water due to the filler being at about mid point of the system.
This, of course, was a standard practice of the day, and although the shortcomings were well known by OEM engineers at the time, I don?t think it was not until electronics became an integral part of engine management that the issue was needed to be fully addressed.

You could put the filler in the top hose by using an in-line filler neck sold by Car Builder Solutions (item INF32). This would go more than half way to resolving the root cause/symptom issue.

Brian Clarke
(1972 Sprint)

[mikealdren]

Stuart,
As Brian suggests, running without a thermostat will give a guide as to whether the thermostat is resticting flow (sticking shut even though they are supposed to fail open!) and causing a problem but don't run without one for long, you want the car to warm up as quickly as possible and the thermostat controls this. Slow warm up accelerates engine wear significantly.

If your cooling is working correctly, the car should run at the remperature set by the thermostat and this should be set to the give the optimum performance for your engine, you don't really want it too hot or too cold.
regards
Mike

[stuartgb100]

When I bought the car 2-3 years ago, the thermostat was one of the first replacements. It took me a while to find one that was 72 degree rated.

I tend to be fairly paranoid about engine temp and oil pressure and therefore watch the guages quite religously !!

I can't believe that I have missed this happening for the last few years, and therefore believe the problem is a recent one. Since nothing has been altered/changed to the cooling system in that time, I'm suspecting the thermostat (which hasn't a small hole, I believe).

Actually, thinking about it, there has been one small change ..... a week ago I used the heater for the first time since last winter.

Regards,
Struart.

[ppnelan]

...one small change...

for driver, one giant leap for car

Matthew

[stuartgb100]

Tried a new slightly warmer thermostat (74 degrees) but it behaved in exactly the same way.

Any ideas ...... ?

Regards,
Stuart.

[bcmc33]

Stuart,

But what happened without the thermostat?


Brian Clarke (1972 Sprint)

[bcmc33]

Stuart,

I found this blog while looking for something else on the forum - it shows exactly what I did to raise the head of the water level to replicate modern thinking and practice.

http://www.steveww.org/index.php?id=26

There are some other interesting subjects as well.

Brian Clarke
(1972 Sprint)