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TR4/4A Tr4a, what engine thermostat for San Diego

Rrbbeerrttoo

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Folks, I would appreciate any comments.
Moss catalog classifies the 160F thermostat for hot weather , 180F for standard, etc. Yet Moss supplemental info. for apparently overheating TR4a says the 160F opens and probably stays open thus coolant flows through radiator too fast, not dropping fluid temp. enough to cool block. I guess someone with heat transfer background can analyse this statement! Or, you experienced folks can help.

Car came with 160F, has also elec. fan, shield around radiator, valves/ timing ok ; everything in engine seems correct ( ignoring the 3 oil drops in tiled floor )but the block and alternator body seem hot...can not touch alt. body after a 30 min. run. I plan to switch to 180F to follow Moss advi as it is simple enough to do! Again I would appreciate your opinions. Yes , I did test the 160F, it opens!

Robert
66' Tr4a Irs
CTC 53788L
 

TR3driver

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Rrbbeerrttoo said:
Yet Moss supplemental info. for apparently overheating TR4a says the 160F opens and probably stays open thus coolant flows through radiator too fast, not dropping fluid temp. enough to cool block. I guess someone with heat transfer background can analyse this statement! Or, you experienced folks can help.

I don't have a heat transfer background (tho I did study it somewhat at Purdue). However based on common sense, the laws of thermodynamics, and conversations with several mechanical engineers, I think the "too fast" theory is completely wrong.

OTOH, running a 160 thermostat does little to help with overheating problems. The thermostat only controls the coolant temperature when the cooling system is removing heat faster than the engine produces it. If you have a persistent overheating problem, then the cooling system is not removing heat fast enough (or the engine is producing it too fast), and there is nothing the thermostat can do about it.

The exception (and origin of the myth) is that, on some cars, with the thermostat totally removed, the water pump can build up enough pressure against the flow resistance of the radiator to blow water out the pressure relief. The thermostat serves as a restrictor, to limit the amount of pressure drop across the radiator. Moss even sells (or used to sell) a blanking sleeve that could be used in place of a thermostat, to prevent the problem.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Again I would appreciate your opinions.[/QUOTE]

Well, what about the radiator itself? I've been through this twice now on a TR3 and TR3A, where the radiator was the problem. Both times, the radiator shop gave it a clean bill of health, said it flowed fine, but in fact it was not transferring heat from the water to the air as it should. Both times, a recore emphatically solved the problem.

The other malady might not affect you, but years ago we had a TR3A that would persistently overheat at freeway speeds. The problem was eventually traced to the carb jets being worn internally. The wear made them go rich only near idle, so when you set the mixture "by the book" (ie at idle), then the mixture would go too lean under cruise conditions and cause the severe overheating. Oddly enough, the engine ran VERY well otherwise. It was noticeably less peppy after repairing all the damage (which may have included changing the rear end back to 3.70 as the car did not have OD), but the overheating problem was gone.
 

JerryVV

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Old radiators can flow OK but the fins may have lost their contact with the tubes and then not transfer the heat from the tubes to the fins and then to the cooling air. Flow is great but cooling does not take place.
 

TR3driver

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JerryVV said:
Old radiators can flow OK but the fins may have lost their contact with the tubes and then not transfer the heat from the tubes to the fins and then to the cooling air. Flow is great but cooling does not take place.
I believe that was the problem with the first one.
However, on the second one, they found that the inside of the tubes all had a thin, fairly even layer of "mud" that was inhibiting heat transfer. All of the tubes flowed, well enough to pass whatever test they use for flow; but when they tried to rod it out (the second time I took it back), they couldn't get the rods through the tubes.
 

macilona

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hello Robert---does your temperature gauge register a higher than normal temperature (hotter than the mid-point of the gauge)? my car would be around the midpoint in comfortable air temperatures and relaxed cruising. but when the summer temperature would get hot, the engine temp would climb when idling, without the airflow from driving. further, if i was on the highway running around 4,000 rpm, the engine temperature would also rise, despite the increased airflow. we switched the thermostat to the 160, but more importantly, installed a new aluminum radiator WITHOUT the crank hole. this increased the coolant circulation by about 20% by freeing up the tubes blocked by the hole, along with the removal of any internal build up in the old radiator that would have reduced the cooling capacity. this made a huge difference---the engine temp gauge now registers a bit on the cool side of midpoint, and when idling in hot weather, it just gets back to the center. this has been one of the best modifications i have done to the car.
 
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Rrbbeerrttoo

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These are great suggestions and I thank you all for taking the time. Now I must look further before responding with substance. As a minimum I will say:

1. Randy, I also took thermo. courses at Indiana Tech in Ft Wayne, and played soccer against Purdue in 1958'-61'. I still understand soccer but the terms enthalpy and entropy no longer mean anything, w/o www.google.com!
I will now investigate the radiator fins' contribution to cooling ( lost contact w/tubes) , that is, if any cooling is provided now! How??, The core tubes were individually cleaned not long ago.
The carb jets suggestion is simple and will follow it up...but was confused at the mention of the rear end damage and 3.7 :1 ratio .
I definitely agree that thermostats do not do much if radiator fail to cool, they may even stay open forever if engine blocks overheats.

2. Macilona, to better respond, I took a long ride today, temp maybe 60F. Yes the gage climbed upwards of mid range and returned to midscale at 40 mph, lower with elec. fan on. I then drove to radiator shop and checked temps..top of radiator 132F, thermostat housing 126F, exhaust manifold 334F. Top 1/3 of radiatorfins were hand warm, bottom 1/2 was much cooler..at full radiator width. For now I will wrap front manifold to keep heat away new alternator.

I still need more info. before deciding on new radiator, although substitution of parts is great way to trouble shoot if parts are handy...otherwise very expensive!

Another question: Does anyone know what actual value temp. sensor resistance is at different coolant temperatures. I used my Simpson voltmeter but do not trust the readings yet.

Thanks.

Robert
66' tr4a irs
CTC 53788 L
 

TR3driver

Great Pumpkin - R.I.P
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Rrbbeerrttoo said:
Yes the gage climbed upwards of mid range and returned to midscale at 40 mph, lower with elec. fan on. I then drove to radiator shop and checked temps..top of radiator 132F, thermostat housing 126F, exhaust manifold 334F. Top 1/3 of radiatorfins were hand warm, bottom 1/2 was much cooler..at full radiator width.
If those are really temps in Fahrenheit, then your engine is way cooler than it should be.

If they are actually Centigrade, then something is seriously blocking circulation, like perhaps a bad thermostat or bad water pump.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Another question: Does anyone know what actual value temp. sensor resistance is at different coolant temperatures. I used my Simpson voltmeter but do not trust the readings yet.
[/QUOTE]
Is the 4A sender the same as the early TR4? For the early TR4, I have 110F = 216 ohms; 185F = 50.5 ohms; 250F = 12.3 ohms.
 

TR3driver

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Rrbbeerrttoo said:
Yes the gage climbed upwards of mid range and returned to midscale at 40 mph, lower with elec. fan on. I then drove to radiator shop and checked temps..top of radiator 132F, thermostat housing 126F, exhaust manifold 334F. Top 1/3 of radiatorfins were hand warm, bottom 1/2 was much cooler..at full radiator width.
If those are really temps in Fahrenheit, then your engine is way cooler than it should be.

If they are actually Centigrade, then something is seriously blocking circulation, like perhaps a bad thermostat or bad water pump.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Another question: Does anyone know what actual value temp. sensor resistance is at different coolant temperatures. I used my Simpson voltmeter but do not trust the readings yet.
[/QUOTE]
Is the 4A sender the same as the early TR4? For the early TR4, I have 110F = 216 ohms; 185F = 50.5 ohms; 250F = 12.3 ohms.
 
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Rrbbeerrttoo

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Randall

Thanks for the info about the thermistor. Its curve climbs exponentially at low temp. My Sympson read 500 ohms around 66F garage temp....and now about the engine F readings:

I bought an infrared gauge to check temps I wrote about erlier. Now must confirm instrument accuracies ( specs say +/- 4 degrees )before commenting with some confidence. For now, tried it in wife's oven, where I got 3 very different readings with oven auto setting ( probably not too exact ), a mechanical/ bimetallic cheap oven thermometer and the new instrument. Another check last evening with the car running in 58 degree outside temp, engine block registered 162F, radiator upper area 155F, exhaust manifold 420F...all readings much higher than original radiator shop. I have left in the 160F thermostat for now.

Who knows if any of these readings will ever meet the black body requirements for infrared instruments. Thanks for all your sharp observations.

Robert
tr4a irs
CTC 53788 L
 

TR3driver

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I believe the sender resistance is logarithmic through the entire scale. Those numbers were actually taken from a TR4 gauge (to confirm that the sender I had was the wrong one). But since that gauge seems to work very well with a proper TR4 sender (sourced from TRF), I believe the numbers are at least pretty close.
 

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