Ford Lehman 135sp coolant question

av8r said:

The item in the photo is probably an oil pressure switch wired to the alternator field.
The coolant pump is on the front of the engine dricen by the same belt that turns the alternator. The thermostat is underneath the coolant reservoir and is accessed by removing the tank.

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av8r said:

No oil pressure, switch is open and regulator is shut off. Oil pressure closes switch and turns on regulator thereby turning on alternator.

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paulga said:

why does the alternator need to be switched by oil pressure?
if there is no oil pressure, the engine does not run, so the coolant pump thus the alternator does not run

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rslifkin said:

It's not particularly necessary, but it's likely done so the alternator doesn't try to produce power right away while starting the engine, making for slightly less load on the starter and a faster start. Realistically, a few second delay on the alternator regulator would work just as well, but apparently that's not how they chose to do things.

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paulga said:

if there is no oil pressure, the engine does not run, so the coolant pump thus the alternator does not run

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av8r said:

The item in the photo is probably an oil pressure switch wired to the alternator field.
The coolant pump is on the front of the engine dricen by the same belt that turns the alternator. The thermostat is underneath the coolant reservoir and is accessed by removing the tank.

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av8r said:

It appears the oil preessure switch has been bypassed and is not in use. You could confirm this by connecting a voltmeter to the field terminal on the alternator and switching the ignition switch on. If you have zero voltage indication with the switch off and nominal 12v indication with the ignition switch on and the engine not running, the oil pressure switch is not in the circuit.
Do the same test with the terminal on the oil pressure switch to see if it is still powered.
Do not connect the oil pressure switch to ground without finding out where it is sourced, if it is a powered wire without fuse protection it could damage your wiring harness by overheating and burning.
I don’t recall if you have external regulators for the alternators. If you do, that’s probably why the oil pressure switch is bypassed.

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petehdgs said:

I have been in the industrial engine generator business since 1979. There are 3 basic kinds of coolant used in the diesel engine world: 1. Heavy Duty coolant with Supplemenntal Coolant Additive, HD with SCAs, this is usually Fuscia in color (pink?) but could also be other colors. 2. Extended Life Coolant, ELC, usually red in color. HD-SCA and ELC coolants both use nitrates to coat engine parts for protection. ELC coolant is more forgiving and requires less routine maintenance than SCA coolant, and it is supposed to last longer and supposedly creates less scale in the cooling system. I cannot confirm this from my experience but I have read it in more than one place. 3. The newest coolant is non-nitrate based coolant. There are abbreviations for these basic coolants but I can't recall them at this time.

The problem I have with non-nitrate coolants is there is not a reliable way to double check their performance while installed in the engine. In my profession, we routinely take coolant samples, and use the analysis to determine if the coolant is suitable for continued use and how much SCA or ELC Extender additive to be used. SCA Coolants need 1200 to 2000 ppm nitrates, and the PH should be between about 8.5-10. ELC needs 250-2200 ppm nitrates and the PH should be between 7.5-9.0. These can all be readily seen by coolant analysis reports, making lon term maintenance of theses coolants straightforward.

Much of this is driven by the trucking industry. HD-SCA coolant is advertised as 3 years, 300,000 miles, and must be regularly maintained with SCA additives. ELC coolant is advertised 6 years 600,000 miles and only needs 1 extender treatment at 300,000 miles. Non nitrates coolant is now advertised for 1 million miles or 10 years. You can see why the trucking industry is flocking to it. BUT these coolants do not 100% fit into these simple categories outside if the trucking industry.

Standby generators and many pleasure boats do not rack up hours or miles like over the road trucks and tugboats.
That should mean the coolant doesn't use up additives at the same rate, and the coolant may last longer. But that requires coolant supervision with coolant analysis and diligent use of coolant additives. My experience is HD-SCA coolant will last as long as ELC coolant if properly maintained, but ELC coolant is more forgiving to lack of maintenance than HD--SCA coolant.

Most engines before 1990 or so came with HD-SCA coolant as factory fill. Some still are. Now many have ELC coolant and some may have nitrate free. The best bet is to keep using what you have OR switch over to ELC on your next engine flush. Take coolant samples and adjust additives accordingly, if your coolant is over 10 years old change it regardless of type. Otherwise sample continue use if the analysis says coolant is OK.

Some of this is my opinion based on experience.
Hope this helps. Clear as mud, right?

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