What are these circles on EMD long hood ends?

[mbinsewi]

Thanks Overmod. I guess I scrolled right past it.

Mike.

[PM_Railfan]

“What are these circles on EMD long hoods?” -

Port holes for hostlers performing reverse moves. [(-D] [(-D]

(i couldnt refuse)

PMR

[CRIP_4376]

I think EMD put them there because they knew it would drive the railfans nuts trying to figure out what they were.

Ken Vandevoort

[Lonloco]

I am a retired EMD Test Engineer. Both answers are correct. The holes are for optional Marker lights and can also be used to access awkward to reach Radiator Vent lines locate high in the Long Hood at the rear.

[BigDaddy]

[#welcome] to the forum. Always good to see someone with real world experience. You are under moderation. I encourage active participation and the moderation passes quickly.

[richhotrain]

I am a retired EMD Test Engineer. Both answers are correct. The holes are for optional Marker lights and can also be used to access awkward to reach Radiator Vent lines locate high in the Long Hood at the rear.

Given that you are a retired EMD Test Engineer and I am not, I will defer to your explanation. However, the optional nature of the holes seems a bit implausable to me.

Were the holes purposely designed to be optional, to be used for either marker lights or as access to radiator vent lines? What if a particular railroad chose to install marker lights? Could the marker lights be temporarily pulled out to reach the radiator vent lines and then put back in place?

It seems to me that the holes were designed to be used for one specific purpose, whatever that might be, but what do I know.

I think the mystery prevails, but my money remains on Ed’s explanation.

Rich

[riogrande5761]

PM Railfan

What do ya think Ed? Bet ya a glazed doughnut (breakfast time here) they are light holes! Better yet, ill make you a deal… if they are maintenance holes - ill tell ya all my secrets on 3d printing. If they are light holes… you gotta tell me your scenery and picture taking secrets… deal?

Oh boy, this is gonna be fun. I just finished making my popcorn, and the butter is being melted on the stove. Let’s get ready to rumble!

Rich

[SD70Dude]

Rich, Randy Stahl has a long history over on the Trains Magazine forum. He is one of the most qualified to comment here on this issue, if practical maintenance on SD40-2s is in question.

Something of interest, here, is that MM&A (one road Randy has long experience on) had four ex-MP (via CN) SD40s. One of these (5364) has both the high-mounted and low-mounted ‘circles’ – so Randy would clearly have been exposed to them.

http://www.rrpicturearchives.net/showPicture.aspx?id=2736410

More interestingly, though, is locomotive 5374, which has high-mounted ‘circles’ but no low-mounted ones:

http://www.rrpicturearchives.net/showPicture.aspx?id=1287709

This promptly points us in the direction of seeing if CN used any kind of classification light in the high position – or what MP might have used when these engines were delivered in August 1973. They were sisters in the same order, builder numbers 73613-1 and 73613-7 respectively, with the unit that would become 5374 originally numbered MP 801 and then 3101; of potential interest is that these then became Union Pacific units (here 4101 in UP paint, which might be compared with Don Strack’s example 3192, built just over a year earlier.)

CN did not order rear class lights or rear numberboards on road thru freight units (GP40, SD40 and larger):

https://i.pinimg.com/originals/2b/b7/6b/2bb76bd96264f4ca0bbaa74eb123bf40.jpg

The secondhand SD40’s that were acquired during the mid 1990s are a bit of a crapshoot, they were all rebuilt to some extent but they all seem to be slightly different. The only thing they have in common is the front headlight was move

[bogie_engineer]

I concur that Dave Goding is the likeliest way to a ‘definitive’ answer from EMD one way or the other.

Hesitant to mention this, but I thought the subject locomotives used an atmospheric-pressure system where the radiators drained completely back into the tank when the engine stopped pumping – do you not read ‘full’ on the gauge glass only then? I thought the necessary ‘siphon breakers’ were the valves accessible through those ports; other vent or radiator arrangements might not have them there.

I’m late to this discussion but since my name is mentioned, I’ll chime in. For reference, I’m retired from EMD Engineering, working there from 1968 to 2015 with a few breaks.

Those blank covers do serve to access the vent line fittings as noted earlier by Lonloco and others, how often they had lights in them and whether that was the original intent, I’m not sure. Contrary to what some RR mechanics think, EMD did consider maintainability in all design work.

The EMD cooling systems are designed so the radiators drain to the water tank when the engine is shut down to prevent radiators from freezing. At idle and low notches, the radiators may not be completely full - the vent lines are connected to a port on the top of the water tank to insure the radiators will fill when the pump pressure is sufficient. At full throttle, there is a small flow thru the vent tubes back to the water tank insuring the radiators are filled.

EMD cooling systems are pressurized with a similar cap to an automotive cooling system, only much bigger. IIRC, the cap is a 12 lb. pressure relief and drains to the pit between the engine and equipment rack where it drains ultimately to the retention tank integral to the fuel tank. However, the design requires that the engine out coolant not exceed 210 deg F at full load at the design ambient, 115 or 122 deg F depending on wh

[fire5506]

[quote user=“bogie_engineer”]

Overmod

I concur that Dave Goding is the likeliest way to a ‘definitive’ answer from EMD one way or the other.

Hesitant to mention this, but I thought the subject locomotives used an atmospheric-pressure system where the radiators drained completely back into the tank when the engine stopped pumping – do you not read ‘full’ on the gauge glass only then? I thought the necessary ‘siphon breakers’ were the valves accessible through those ports; other vent or radiator arrangements might not have them there.

I’m late to this discussion but since my name is mentioned, I’ll chime in. For reference, I’m retired from EMD Engineering, working there from 1968 to 2015 with a few breaks.

Those blank covers do serve to access the vent line fittings as noted earlier by Lonloco and others, how often they had lights in them and whether that was the original intent, I’m not sure. Contrary to what some RR mechanics think, EMD did consider maintainability in all design work.

The EMD cooling systems are designed so the radiators drain to the water tank when the engine is shut down to prevent radiators from freezing. At idle and low notches, the radiators may not be completely full - the vent lines are connected to a port on the top of the water tank to insure the radiators will fill when the pump pressure is sufficient. At full throttle, there is a small flow thru the vent tubes back to the water tank insuring the radiators are filled.

EMD cooling systems are pressurized with a similar cap to an automotive cooling system, only much bigger. IIRC, the cap is a 12 lb. pressure relief and drains to the pit between the engine and equ

[gmpullman]

I recall asking this to someone familiar with locomotive repair and was told that they were access holes to get to fittings on the vent lines to the radiators located behind them.

---

The upper covers were to access the vent line at the top of the radiators.

Thanks for confirming what I understood was the function of the access holes.

Regards, Ed

[mvlandsw]

Doesn’t the rubber gasket mount make them hard to remove and replace? It seems to me that a bolt mount like shown here would be easier to use.

http://www.rrpicturearchives.net/showPicture.aspx?id=1319920

Mark Vinski