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post #1 of 16 (permalink) Old 07-09-2015, 06:11 PM Thread Starter
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Car running hot

I am in Texas, so I removed the thermostat. But the car still running hot. The coolant overheat warning lamp is not on though. If idling, the temperature is fine, about 80 Celsius degree, but after running around a few minutes at 40 miles per hour, I measure the surface temperature of the thermostat housing using the infra red thermal meter, it could go up to 110 celsius. But still the coolant is not boiling. Is this temperature normal, it's kind of hot, I think.

BTW, I replaced the fan clutch with a "good used one " from Flying spare. And this is the situation after the replacement. Before this, the old fan clutch is totally gone.

Thank you guys

75 Silver Shadow LRD21XXX
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post #2 of 16 (permalink) Old 07-09-2015, 08:13 PM
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First, I don't care where you are, you should never run these cars without a thermostat because running cold for long periods is far worse than running a bit hot (but not overheated) is.

The Crewe Original U36600 thermostat is supposed to open at 88°C/190°F and will not be fully open at that temperature. The radiators in these cars have more than enough cooling capacity to keep the car running at its ideal temperature (in consort with the thermostat, which controls how much/how quickly water circulates through the radiator versus the bypass port). A 40 MPH driving speed takes the fan entirely out of the equation anyway because the ram supply of air is more than the fan could ever hope to pull through he radiator.

Where is the needle on your temperature gauge. Anything within "the white band" is within normal limits. What's it showing when you have a 110°C reading at the housing? That does strike me as toward the upper range of normal, and without a thermostat you should never even be getting close to that.

I would suspect that your radiator may need to be recored or, at a minimum, acid flushed to remove water deposits that have likely formed over the decades (and particularly if someone decided that using way more water than antifreeze was the way to go).

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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post #3 of 16 (permalink) Old 07-09-2015, 11:32 PM Thread Starter
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Thank you for the reply.

The car does not have a coolant temperature gauge, it only has a warning lamp for the coolant overheat. And there is a coolant overhear sensor mounted on the passenger side cylinder head.

The 110°C reading is the infra red thermal reading at the housing. And at this point the coolant isn't boiling.

The infra red thermal meter should be accurate enough, i tried pointing it at the boiling water, it reads 98-99 °C, never above 100.
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post #4 of 16 (permalink) Old 07-09-2015, 11:46 PM
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I'm waiting for additional confirmation, but it appears that the "hot operation" range should be approximately 88°-100°C/190°-210°F. The SY cars should run within the same operating temperature range as the SZ cars, and those are documented in, Thermostat Issues and Selection. (Disclaimer: I am the third author of that article. I'd forgotten that Don had documented the "full open" temperature for the thermostat and, at that point, the car should be able to maintain that temperature fairly steadily (not perfectly, but fairly steadily).

If you're getting up to 110°C/230°F you appear to be running hot.

The first thing I would suspect is that either your radiator and/or engine cooling passages have developed hard water deposits over the decades and can no longer transfer heat as efficiently as they should. The instructions for doing a citric acid flush of automotive cooling systems are "out there" on the web. That's probably what I'd try first to see if it makes any difference in your heat transfer characteristics.

More information if I get anything useful over the next couple of days.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr



Last edited by guyslp; 07-09-2015 at 11:48 PM.
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post #5 of 16 (permalink) Old 07-09-2015, 11:54 PM
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There is another reason you should put the thermostat back in. When the engine is cold, water is circulated through the engine by the water pump via a bypass port. As the engine heats up, the thermostat allows water to flow in from the radiator but also starts to close off the bypass port. When hot, the radiator valve is fully open and the bypass port fully closed. By removing the thermostat both pathways for the water flow are fully open on a hot engine. The hot water cannot circulate fully through the radiator as a proportion of it is being directed straight back to the hot engine through the open bypass port. It's really not a good idea to run without a thermostat on these cars.

If your thermostat is faulty check out Brian's resource file for a replacement:

https://docs.google.com/file/d/0B61g...zE1/edit?pli=1

Geoff
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post #6 of 16 (permalink) Old 07-10-2015, 01:59 PM
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More information has arrived. Last night I reviewed, Thermostat Issues and Selection, and found that Don Elliott had included information regarding the melt-out temperature of the lead plugs and other temperature characteristics of the OEM UE36600 thermostat. Given that it's been a couple of years since we worked on this research, and that part was "his part," I e-mailed asking for specifics regarding where the data came from:

Sure, the 124 C temp was cited in TSD 4700 page L5-1 middle of the left hand column. The Crewe UE thermostat begins to open at 88 C and according to this same page is fully open at 102 C. The normal operating temperature is given as 99 to 102 C. [I should also note that there is an error in the Shadow series documentation that repeatedly says the thermostat opens at 80°C, which has never been correct and apparently was never caught over multiple decades of reprinting.]

Since all of the temperature regulation is controlled by the thermostat, at least if all is functioning as designed, the same data should apply to the SY cars as well since they all use the same thermostat.

This means that the normal "settled down" operating range is approximately 210°-216°F. There is, of course, the potential for a bit of "slop" at the top of a few degrees if the individual thermostat in question doesn't reach full closure at the noted temperature. They aren't precision instruments and while they are individually consistent in their behavior, different examples can vary +/-5% and still be considered OK. I doubt that there is any testing on these things at the point of production, so if you want to know what your current or intended replacement thermostat's temperature response actually is you'll have to test it out yourself on the stove top.

Given that the plug melt-out point is very well above the normal operating temperature range, I fully expect that there can be some "spikes" that are above that range under demanding conditions in hot weather but that should never even come close to getting near the melt-out point, which is a full 40 degrees F above the top of the ideal normal operating range.

FYI, there's no good reason to replace the fan clutch in these cars with used ones. New ones that are commonly available are activated at the correct temperatures. These are documented in the RR & Bentley Parts, Repair, Restoration & Other Resources Compilation as well as in threads on this forum and the RROC-Australia Discussion Forums.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr



Last edited by guyslp; 07-10-2015 at 02:03 PM. Reason: Fan Clutch comment
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post #7 of 16 (permalink) Old 07-10-2015, 03:16 PM
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The replacement fan clutch in my 1975 Shadow is a Hayden 2747 (UPC 036752027477) which I am told also fits the mid-1970s Chrysler Imperials.
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post #8 of 16 (permalink) Old 07-11-2015, 08:06 PM Thread Starter
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Update: installed the stant 13558, as described in the "Thermostat Issues and Selection." Still the same, after running a few miles, the surface temperature of thermostat housing is about 110 degree Celsius, I also measure the temp for the surface of the coolant reservoir, it reads about 98-100 °C. the lower radiator hose (metal part) also reads about 100-105 °C.

75 Silver Shadow LRD21XXX
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post #9 of 16 (permalink) Old 07-12-2015, 09:51 AM
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I have tried everything to prevent my '84 Spirit from over heating...to no avail. Cooling system flush, Stant 13558 thermostat, electric fan function, thermostatic fan function, nothing had the slightest effect on reducing the problem of SEVERE overheating at idle...boiling coolant. Just about the only thing left is the water pump, but it doesn't leak, so that too, is unlikely. However, I did the old "shining a drop light through the radiator/evaporator" and couldn't see ANY light. The grille was off so I ran the garden hose, full blast, from the front of the evaporator through the radiator...NO water came through except a few drops around the edges. I scrubbed the front of the evaporator with a stiff brush and strong soap. A LOT of nasty stuff washed out, but the water test still wouldn't allow water through. Next step is to see if I can unbolt the evaporator and see if I can lift it up enough to get at the radiator to try and clean that. Since this problem has gotten steadily worse over the past few years, I believe I might have found the problem. Not getting ANY water through the evaporator/radiator cores with a full blast garden hose REALLY surprised me.
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post #10 of 16 (permalink) Old 07-12-2015, 11:39 AM
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Quote:
Originally Posted by 345 desoto View Post
I scrubbed the front of the evaporator with a stiff brush and strong soap. A LOT of nasty stuff washed out, but the water test still wouldn't allow water through.
Your best bet is to soak the radiator or condensor coils down with a strong solution of Simple Green (or similar, making sure whatever you use is compatible with any bare metal that might be exposed) and giving that a chance to soak in and loosen any caked on grime.

You also might want to consider using a spray head for your hose that has a "center" setting like my Melnor one has. This creates a very strong pin spray that's much better at blasting stuff out of small cracks and crevices than a full blast does (which just tends to break up on contact with the surface).

You are correct that if you're not getting any air, or even not enough air, through the cooling fins then you will definitely overheat.

Brian

The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.
~ Niels Bohr


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