Overheating ????

[Mikey likes it!]

My TC runs hot over 2500rpm.   I have changed/checked the thermostat, radiator, water pump flow from heater valve and air in system .  It started with a new temperature sensor,  the old one was broken, the tab coming off the sensor would spin 360.  At idle it runs cool 90-95 c,   at higher speeds it runs hot.  My feeling is the old sensor did not work at higher temps....  The new sensor has the same part number as the old one.   I am trying to check the timing,  I have a petronix distributor with a vacuum advance and centrifugal advance. With the vacuum disconnected,  it shows 12 on the flywheel, at 2500 it shows 20 and 3500, 30 degrees.   Could the timing be causing the overheat problem ?  Any ideas ?

[Clifton]

Higher speed as in mph/kph or just rpm? I know you said checked/changed radiator, ect but every cooling issue I have had at speed when the engine was under load, about 40 mph was radiator related. Cleaning them wasn't enough.  Replaced and all was good. Your timing would have to be so far off that you would be pretty deep into the throttle maybe not WOT but you would know.

[Lotuswins]

Sounds like a wrong/bad sensor if no other symptoms exist.  90/95C is not cool, mine runs at 75C with a 160F thermostat.  Have a temp gun to check head external temp?  have you removed and checked in boiling water?  Also, is it connected to 10V voltage regulator? 

Jerry Rude
4005R

[Mikey likes it!]

It is connected to a10v stabilizer.  It has never ran at 75 c.   Tomorrow I will check the ground on my voltage stabilizer.  I did check the thermostat with a new one on the stove, both opening at the same temp in hot water.   I appreciate the advice.  Thanks

[BDA]

Check the voltage between the voltage stabilizer and the gauge with the ignition on but the car not running to check the stabilizer. Do you have a new solid state stabilizer or do you still have an old one?

[Mikey likes it!]

I have a new stabilizer.   Purchased in the past year.  I will check the voltage as you stated in the morning.....  According to my meter.. the stabilizer is not the problem.

[literarymadness]

According to the Miles Wilkins book, Stromberg Twin Cam engines run about 5 degrees hotter than the Weber version and should not generally exceed 95 degrees Centigrade.  I find that a better fan makes all the difference.  I have a Spal  fan on my TCS. My car's temperature at idle is usually about 87 C. At high revs around 92 C.  My TCS used to have a heating problem but I switched to an aluminium radiator with a more powerful fan and it solved the problem.  My friend's TCS has a similar setup and posts similar temperature numbers. He has twin Spal fans mounted to a shrouded radiator on his car.

[Roger]

Vacuum advance is really non-standard for a TC.
May I ask why? What is maximum advance, centrifugal + vacuum?

[jbcollier]

Federal TCs came with a vacuum retard for emissions.  Common, and wise, to leave it disconnected.

[jbcollier]

Gauges are useful indicators of what's going on but they are not calibrated, scientific instruments.  Get yourself a cooking thermometer and calibrate it using boiling water (use google to figure out how to compensate for local altitude).  Use the now known-good thermometer to check your thermostat.  Install the thermostat and note on the gauge when it opens (hot water in pump outlet hose).  Is the gauge accurate?

[buzzer]

does the water system pressurise? as that is a basic indication of temperature. I had a new sensor and my gauge reads up to 110c! I was initially worried by this,  but I am convinced I am reaching at max about 90-95. the water systems does not pressurise, I also put a tell tale engine sticker on the head  for 90c and that has never triggered. and I have a infrared temperature checker. The fan responds correctly to switch in and out.  I will at some point change the sensor and voltage regulator.

[Mecky]

Possibly there is a big air bubble in the system and it can't build up pressure. In that case the water stays more or less in place, instead of being pumped. That would mean that there could be a bunch of very hot water/air (at the measuring point for the gauge) inside the engine, while the rest of the water is stone cold (close to ambient temperature), but no flow of coolant is provided.

[Pekka]

My S2 with Weber runs hot. I have a fan mounted in front of the rad that keeps it 90-95. In summer and in traffic without the fan it will boil over. Fan has a sensor and manual switch on dash.

[jbcollier]

The stock S1 and S2 rad fan is USELESS.  It was designed to "pull" air through the rad.  Lotus wired it so it would run backwards and "push" air through the rad instead.  Fan blades are curved like an airplane prop.  They work well in the proper rotation and work poorly in the reverse direction, probably down to 30% of what it will move in the right direction.  Take the old fan off and save it for the concours.  Buy a more powerful, pusher fan and you will be amazed at how much better it cools.

[Pekka]

Thanks for posting this JB. It has a new fan (20 years old “new”) but I might invest in a new one. Mine is sure noisy but at least I know when it’s on. The fuse blows often...