I've got "heat creep" !!!!

[tedtaylor]

My '73 Elan Sprint, 40K original miles, twin Strombergs, headers, points, wider Triumph radiator, I have flushed cooling system twice, installed new thermostat (180 degree), have 50/50 antifreeze, runs normal operating temp at 85-87 degrees on gauge.
PROBLEM: I have case of "heat creep" in that while driving on a hot day, (85-90 ambient air temperature), at a constant 65MPH (3750 RPM) for the first 20 minutes, normal 85/87 degrees on gauge, The next 20 minutes temp on gauge "creeps" up to 90. Then 20 minutes more it creeps higher to 93 degrees on gauge. Then nearing 95 degrees on gauge.
If i put the heater on (interior heat), the temp drops back to normal (obvious source of extra cooling to system). I turn heater off, temp creeps back up.
Now when i pull off the interstate back to secondary roads and lower speeds, the temp quickly comes back down to normal.
Clearly constant speed (65 MPH / 3750 RPMs) during warm/hot days (85-90 degrees) for prolonged periods, I definitely get this "heat creep" that concerns me and i have no explanation for or remedy.
I have side blanking panels and foam across the hood at the radiator, I have the side wheel well vent holes too.

Any suggestions what to look for?
thanks
TED

[elanfan1]

I'll start with my usual 'I'm no mechanic' but I'm wondering are you looking for a problem that doesn't exist? I suspect a lot of owners would love those temperatures. Awaits being corrected...

[elansprint]

Ted I think most cars are marginal on cooling on really hot days not usually a problem in the UK very often. I fitted a ticker core to my radiator which improved the cooling what I find strange with your is it over heats at reasonable speed on the interstate when there should be good airflow through the rad yet runs cooler at presumably lower speed on the side roads mine was exactly the opposite ? It does sound as if you are not getting enough airflow through the rad at higher speeds. With the wider rad is the whole width seeing airflow ? Do you have engine driven or electric fan ?
Ian

[Apx]

i had the same problems, two quick issues mine showed up which helped with a similar problem. Firstly make sure that the airflow is going through the radiator and not around it, plug up the holes . Secondly which i only found on an engine rebuild was that 50% of the blades of the water pump had corroded away making it not very efficient at circulation. How you diagnose this with out taking the engine apart i do not know. Mine has no cooling issues now.

[pharriso]

There's no such thing as a '73 Federal Sprint, last production was July 1972

[tedtaylor]

Phil, my Sprint (#0297K) manufactured July 1972.....BUT sold later in the year, thus titled 1973
Ian, I have BOTH an engine mounted fan AND electric fan.
as you mentioned, air flow through radiator at speed should not be the issue since i have side block plates AND the wider Triumph radiator and foam strip across top (on bonnet lid).

I do have a lot of "stuff" forward of the radiator, but where else would it go?

[wotsisname]

Electric fan rotating in the correct direction ?

[EPA]

Have you checked to see if the radiator is getting hot throughout its area , in other words are there any relatively cold spots to the touch which might indicate that the core is partially blocked.

Ed

[pharriso]

Electric fan rotating in the correct direction ?

That's a good suggestion to check! The fan should be pushing air through the radiator.

Ted said "Phil, my Sprint (#0297K) manufactured July 1972.....BUT sold later in the year, thus titled 1973 "

The MY on the title should the same as the legal model year certification of the car, what does the emission plate say under your hood, 1972 or 1973? The state that first registered the car screwed up...

[tedtaylor]

Yes, fans are correct direction, but fan is NOT operating while at speed (or until reaching whatever mark the otter sensor is set for)
Radiator hot throughout, no cold spots.
Phil, I've come across many cars (Lotus especially) where they are titled when sold to first customer, so if the car was sitting at the dealership until late Fall (that's when the new model year designation is made), then they get titled that new year.

I was wondering if this is a sign of a rebuilt motor with bigger bore? Do "hot" motors run hotter?
In the end, i'm thinking the actual fluid capacity of the cooling system is too small (maybe 2 gallons?) so that eventually, the entire system is at 180 degrees (thermostat temp) without ability to cool down, the thermostat is then always open and the whole system temps keep rising? Perhaps if my capacity were larger. This line of thought comes from when i turn on the interior heat, the temp drops, so that "closed" capacity was able to be cooler (out of circulation). Get where I'm going here?

[seniorchristo]

Ted
My car has dual fans, well shrouded and runs around 180 F under similar conditions. Perhaps your fan is a little on the small side.
Can too much ignition advance cause overheating?

[gjz30075]

Ted, first verify your temps with an infrared temp gun. When you stop, needle is at 'x' degrees and take
a reading right at the temp sending unit bulb at the head to verify the gauge.

Good question about a 'hot' engine. I have a 1720cc motor, 150 hp at the flywheel, and constantly run
between 90 and 95c at highway speeds. Probably 'correct' for what it is. However, it remains constant
and doesn't climb.

Good question about the timing. Maybe it's going beyond maximum, which I'm guessing should be about
mid 30s degrees, depending on your distributor type and any mods within.

Even with the temps verified, I understand the concern about the rise in temp, not necessarily the temp
itself.

[StressCraxx]

Ted
My car has dual fans, well shrouded and runs around 180 F under similar conditions. Perhaps your fan is a little on the small side.
Can too much ignition advance cause overheating?

Too little advance (timing retarded) or no advance will cause high temperatures.

[holywood3645]

A little off topic, I rented a car lat week (SUV) GMC for a drive to N Cal.
I was a little surprised at the temp. It ran 210 F (99C) the hole journey (I though it was high)

James

[tedtaylor]

the design of modern vehicles most always run above boiling temp.... high pressure systems (16 - 20 pounds) prevent water from boiling over. at least that's what i've been told.