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  #1   IP: 152.163.100.136
Old 01-17-2005, 12:48 AM
eric 352 eric 352 is offline
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Unhappy installed alarms now engine temp not right

don
i installed the over temp and low oil alarms on my a-4 in a 74 ericson 35 II. the engine is located under the dinette. i installed the over temp with the parts that were supplied. the t is mounted horizontal to the head on the right side(generator side) i have the temp sensor mounted. on the left side i have the over temp sensor.
i ran the engine for about 20 minutes and the dash gauge never got to 120 degrees. using an infa-red digital thermometer the head reads 159 degrees. the tee reads 115 degrees and so does the temp gauge on the dash. i was thinking that if i installed the tee vertically then there would be an air pocket at the sensor, so i mounted it horizontally.

is the tee mounted correctly? if so how do i get the gauge to read the actual temperature of the engine ??

thanks
greg
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  #2   IP: 206.48.20.86
Old 01-17-2005, 04:02 PM
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Greg,

Your horizontal "T" fitting is mounted properly.

The temperature of the water passing up through the thermostat (and past the temperature sender) in a late model engine, is a composite of all the different temperature zones throughout the block and head. It's not at all uncommon to see a somewhat cooler temperature at the sending unit than the hotter zones in the block or head; and, the fact that your sending unit and cockpit gauge are so close (115 versus 120 degrees) is a good indication that the sending unit and gauge are functioning satisfactorily.

Best regards,

Don Moyer
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  #3   IP: 205.188.116.134
Old 01-17-2005, 10:32 PM
eric 352 eric 352 is offline
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don thanks for the answer to my 2 questions.

although everything is installed correctly, i don't feel comfortable with the difference in readings. there is a 44 degree difference between the actual temp of the engine and the gauge reading. the temp reading at the over temp sensor was the same as the temp sending unit. inside the tee the senors are only 1/4 inch apart.

what i don't know is:
1. at what temperature does the overtemp alarm go off.
2. at what temperature is the engine considered overheated to the point of being damaged .

if the over temp goes off at lets say 190 degrees, then according to the readings the engine temperature would be 190+44=234 degrees.

do you know how far the threads for the tee go into the water jacket ? could it be possible that they go into the jacket too far and the tee acts like a deflector and the water circulates around the tee ? is there another place on the engine that either one of the sensors can be installed. i don't feel comfortable relying on an untested alarm sensor that will go off after its too late.

i have one other question. what brand and what is the part number for the oil sending unit ?

thanks
greg
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  #4   IP: 206.48.20.86
Old 01-18-2005, 03:00 PM
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Greg,

If I understand your question correctly, you apparently remain concerned over the difference between the highest temperature readings you are observing on your cylinder head with your hand held laser temperature probe and the indications you're getting on your cockpit gauge.

I may be repeating myself, but the temperature indication you get on the cockpit gauge is not a measure of the hottest place(s) within the engine, but rather a composite of the temperature of the water as it moves through the cooling jackets to transfer and remove the heat build-up within the engine. This is no doubt why engine temperature gauges have "water temperature" written across their faces rather than "engine temperature". More importantly, if the water temperature were not cooler than the engine temperature, it could not transfer heat from the engine.

Many folks are surprised to learn how hot various places can get on late model raw water cooled engines. On these engines, temperature is maintained through by-passing part of the incoming cooling water around the block and head and directly to the manifold, leaving the circulation within the block and head somewhat reduced. This reduced flow in general can result in localized areas of somewhat static movement of cooling water, even in engines with relatively clean water jackets.

NOTE: The "recirculating" cooling systems of early model engines tend to maintain a more even temperature within the block and head. In these systems, the full flow of water from the pump is circulated throughout the block, head, and manifold. Temperature is controlled by recirculating part of the cooling water back through the intake of the pump by an external Dole thermostat, but the full flow from the discharge of the pump flows through the engine in all cases.

In terms of how high localized temperatures can get in a late model engine, we have received many reports in the range of 250 and even 275 degrees with no ill effects. Until the person took the readings, there was no indication of any high temperature condition, and in all cases, water temperature indications in the cockpit were completely normal. The fact that engine temperature always exceeds the temperature of the cooling water is the reason that engine water temperature may be observed to go up (sometimes called temperature overshoot) for the first few minutes after shutting an engine off, until the temperature between the engine and the water equilibrates.

With respect to your other questions, the temperature alarm is set to activate at water temperatures in the range of 210 degrees. We sell both Stewart Warner and ISSPRO oil pressure sending units. The product number of the ISSPRO unit is GAUG_12_181, and for the Stewart Warner, GAUG_04_94.

Best regards,

Don Moyer
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  #5   IP: 64.12.116.134
Old 01-20-2005, 01:00 AM
eric 352 eric 352 is offline
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thanks don

i understand what your saying about the temperature around the head being different. before i installed the tee and other sensor the water temperature passing the temp sensor read 165 degrees on the temp gauge. wouldn't you agree with all else being the same the water temp passing the tee should be 165 degrees.

if the above is true then there must be an air pocket inside the tee to prevent water entry into the tee, or the threads on the tee potrude so far into the head that it acts like a deflector and the water goes around the tee.
on my ericson 35 II the engine is at max angle which could be the reason for such a difference in temp readings.

do you have any ideas on how to solve my problem ??

thanks
greg
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  #6   IP: 206.48.20.86
Old 01-20-2005, 10:13 AM
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Greg,

We have had reports from folks that after moving their temperature sender from the head, and placing it in one of the branches of a "T", that they did notice a small "before and after" variation, but the variations have been in the range of 10 degrees or so (cooler) after installing the "T".

I'm not sure why your average readings would go from 160 degrees down to 115/120 degrees, but this variation is much greater than we have ever had reported previously. Are you sure that there are no other variables?

Best regards,

Don Moyer
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  #7   IP: 206.48.20.86
Old 01-20-2005, 10:14 AM
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Greg,

As a follow up thought to my previous message, it seems to me that you could determine whether or not air is trapped within the "T" by simply loosening the sending unit to see whether any air comes out.

The variables to which I was referring relate more to operating conditions, outside water temperature, whether or not you did any other maintenance to the cooling system, etc.

Don
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  #8   IP: 216.69.227.7
Old 01-20-2005, 02:24 PM
Davis Modlin Davis Modlin is offline
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I was reading this thread and could help but wonder that if the sensor not being in the direct flow of the water. the bulk of the water may be flowing right past the T fitting and not into it thus the strange readings.

Just a thought

Davis
DMA4
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  #9   IP: 206.48.20.86
Old 01-21-2005, 11:33 AM
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Davis,

Good thought, but we simply have no history of large (or otherwise strange) temperature variations on cockpit gauges when we move a sending unit out of the direct stream of engine coolant - at least no larger than the 5 to 10 degrees I mentioned previously. In addition to facilitating the doubling up of sending units and over-temp switches, it's very common to use "T" fittings to install a sending unit in the cooling systems of early model engines.

One of the reasons that "T" fittings don't impose more of a variation, I suspect, is due to the high conductivity of brass. Whenever I measure the temperature of a "T" and the nearest metal directly behind the "T", the temperature is virtually the same.

Regarding the specific concern of whether or not air can get trapped in "T" fittings, and whether or not the air is actually affecting temperature readings, the question can best be answered in specific applications by simply loosening the sending unit to "burp" any air out that may be present.

Best regards,

Don Moyer
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