Hi Bob and Dick,
All very good advice Dick. The rule of thumb for the radiator I was taught
is it should be able to empty itself within 4 - 5 secs from full. I
normally have the radiator out of the car for this test, but I cover the
bottom outlet, fill to the brim, and time how long it takes to drain.
I had a similar temp creep problem with my saloon Triumph a couple of years
ago. My old radiator was dying so I had it recored, but this made the
temperature creep problem worse. To cut a long story short, it turned out
that the radiator shop had used the wrong paint on the core. The result was
the paint had a much higher thermal resistance so the heat wasn't being
removed from the radiator as efficiently as it should have been. This only
showed up at idle with the low airflow through the radiator. The shop who
did the work made good the repair by stripping and repainting and all was
as it should be.
Regarding the electric fans..
I have recently installed an electric and removed the crankmounted unit in
my Triumph saloon (to enable installation of power steering). The electric
fan came out of a Mitsubishi van and draws around 5 amps. I have used a
thermoswitch out of a 1980 Honda Civic which turns on at around 90deg C
(194 deg F) and off at about 85 deg C (185 deg F). The thermostat in my car
is 82 deg C (182 deg F). The thermoswitch is the correct thread to bolt
straight into the thermostat housing on the opposite side to the
temperature sender. On the PI cars, there is normally a blanking plate in
here, but I think on the carbed motors it is used for the preheater or
similar.
Although we are in Autumn, the outside air temp is still around 20 ~ 25 deg
C (68 ~ 77 deg F). I find the fan only comes on when stopped in traffic
after about 5 minutes or stop start driving. When it does come on, it does
so for about 30 seconds and then off for around 1 minute. The only
disconcerting thing is watching the temperature gauge rise up to around 3/4
before the fan comes on. I have also installed a manual override switch
(yeah ok, I don't trust it 100% yet).
All up the installation of the fan cost me about NZ$50 using secondhand
parts from a wrecker.
If anyone is interested, I can email them a jpg of the circuit diagram. I
hope to have a web page up and running in the near future so will put some
photos up about this.
Hope this is helpful.
Regards,
Bernard Robbins
71 2500 PI (soon to be EFI)
73 TR6 PI (can't wait to get it back from the bodyshop!!)
At 00:30 29/04/00 -0700, Sally or Dick Taylor wrote:
>Bob---Well you certainly wrote plenty of information about your latest
>concern, but I, for one, would like to include a lot of questions to be
>replied to at your convenience. The information needed will include
>some of the possible causes.
>
>1. Did the overheating start when the compression was raised, OR after
>the cam was changed? Did you install a stock grind cam?
>
>2. Is the thermostatic vacuum control tubing still connected to the
>distributor retard? Does it work?
>
>3. What does the temp "creep" to? (It's normal for most TR's to move up
>a half notch on the gauge when idling for a while. (But not in a
>"minute, or 60 degree outside temperatures.")
>
>4. What's the pressure rating of the radiator cap? (7 lb. is OK, but
>13lb. allows a higher temp before boiling starts.)
>
>5. Is your radiator shroud in place?
>
>6. Has the radiator itself been tested for flow rate lately?
>
>7. I will assume it starts to overheat even with the "air" off.
>
>8. Can you go back to a place in time when this was first noticed? Often
>it happens when a certain part was changed, or an adjustment made that
>influences the cooling of the engine.
>
>9. Does the fuel line come in contact with anything hot? (Loss of rpm's
>as temp rises could mean possible fuel boiling.)
>
>10. Engine run-on is common if the anti-run on feature isn't connected,
>especially if the idle is set too high.
>
>11. Replacing your thermostat to one with a cooler rating (165 degree)
>will buy a longer period before the "creep" goes past the half-way point
>of the gauge, but won't likely stop the creep.
>
>I don't think the answer lies in the points, valve adjustments, carb
>tuning, or the like.
>
>I know there are many owners that feel they needed a supplemental way of
>keeping their engines cool, either by larger radiators, or extra fans.
>I've never had the need, but maybe it's just dumb luck. Raising the
>compression ratio may have been at least part of your cause, but I can't
>believe this alone would be the only thing going on here. Modern engines
>typically run much warmer than they did 25 years ago, with no ill
>effects. I do know there's a confidence window when it comes to water
>temperature, and those of us that watch our gauges don't want it on the
>outside. Please let us know what you find after reviewing the above.
>
>Dick Taylor
>'73
>L.A., Ca.
>
>
>
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