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Kohler 7.5R62

ctd01

Registered
I picked up a 1985 kohler 7.5r62 gen set last year. I'm finally getting time to mess with it. It has 158 hours on it. I hooked it up to a propane tank and it fired right up. This thing runs like a wrist watch. So for good measure I pulled the radiator sent it out to be cleaned and pressure tested. I'm going to change the belt and all the hoses. I also would like to change the thermostat. I can only find a 44 mm tstat in 160 or 180 degree temp. Stock that came out was 170. I'm thinking go with the 180*. Im planning to but this unit in a gen box and use it as a standby unit with an auto transfer switch. Any help or suggestions about this unit would be great. Pics to come!
 

Zephyr7

Registered
Since no one else has answered, I’m going to say “180 should be fine”. You’ll run a teensy bit higher pressure on the coolant, but probably not enough higher to cause any issues.

Bill
 

ctd01

Registered
Yeah I didn't see it being too big of an issue. Radiator shop said they got the radiator flowing real well. I can believe Kohler would use such a big engine for 7kw. Seems like over kill but it should last for ever.
 

Vanman

Subscriber
Last Subscription Date
06/10/2020
A 7-1/2 should be the L654 engine. I believe those are around 65 ci? Have to look that up. The L600 is right close to 59 ci IIRC.

I wonder if a set built in '85 would still have used a selenium rectifier for the auxiliary field circuit. A photo of the inside of the controller would tell all. You can't miss it. It would be a large finned device.

If it is there, you'll want to replace it with a silicon rectifier. :brows: The selenium ones fail merely with age. In this circuit it's failure will cause expensive collateral damage.

Keith
 

Zephyr7

Registered
Probably unlikely you’d see a selenium rectifier in 80’s vintage equipment, but it’s easy enough to check so better safe than sorry. I think selenium rectifiers were pretty much phased out by sometime in the 70’s.

You’ll probably have an older style silicon rectifier in the 80’s vintage gear. That rectifier will probably be ok, but if you’re doing an overhaul it wouldn’t hurt to replace it with a newer part.

Bill
 

ctd01

Registered
Any specific brand to buy? Are some better then others? I'm good with the engine part of it but, am still learning on the gen side.
 

Zephyr7

Registered
Any specific brand to buy? Are some better then others? I'm good with the engine part of it but, am still learning on the gen side.
If you’re referring to the rectifier, I’d just get one of suitable ratings from any of the reputable electronics suppliers (digikey, mouser, etc). I would NOT buy one of the chinesium rectifiers on amazon or eBay.

Bill
 

LWB250

Registered
1985 would be an L654 and most likely a former Bell Systems trailer unit.

These things are built like brick doghouses and will easily do 5,000 hours or more if properly cared for. Parts are getting harder to find and more expensive, but again, they're near impossible to kill.

Dan
 

LWB250

Registered
Yes it's an l654. Proper care as in what? General maintenance and such?
Exactly.

The Bell System units, typically installed in the yellow trailers manufactured by HESCO, would easily see 10,000 hours before they were retired or parted out for spares for newer units.

These things were built like brick doghouses and would go and go and go as long as the oil and coolant was changed regularly and normal maintenance done.

Dan
 

ctd01

Registered
Yes I'm a maintenance freak. What is your guys recommendation for oil change intervals? 50-60 hours?

As for coolant once a year is my plan.
 

G Sams

Registered
For me it depends on IF it has an oil filter, IF it's gasoline or propane powered, IF it has an oil bath air filter or dry element, operating conditions, and how often it's used.
 

Zephyr7

Registered
Yes I'm a maintenance freak. What is your guys recommendation for oil change intervals? 50-60 hours?

As for coolant once a year is my plan.
The general rule for oil changes on generators is every 100 hours or every year, whichever comes first. That assumes equipment with a filter and full pressure lube. Splash lube would probably need changes after fewer hours, but the yearly part would still be ok (maybe every 25 hours or every year, whichever comes first).

The general rule for coolant depends. I usually say to do every 5 years unless you have problems, and you can use a refractometer to test it. I do 5 year scheduled changes on my own equipment. I don’t see any reason to do yearly coolant changes. For coolant you’re mostly concerned with the corrosion inhibitors. For a properly sealed system, those should last a while.

I use a full synthetic 15w-40 oil in my own gensets, but you might need something different in yours depending on conditions. You want a good additive package for the older equipment too.

Bill
 

ctd01

Registered
Coolant pH is my main concern. Most cars and trucks we do a 2 year interval before the coolant starts to get acidic. It's cheap enough to do oil and coolant at the same time. I may run the same oil in my gen as my tractor. I run rotella t5 10w30.
 

Vanman

Subscriber
Last Subscription Date
06/10/2020
What are you guys using to test your coolant? That's something I really need to learn how to do.

We did a valve job on the Cummins in our bus when we bought it ~10 years ago. Sadly it's only been run ~1000 miles since, and so the coolant hasn't been changed since either. It holds ~15 gallons, so knowing without question if or when to change it would be great.

It has a coolant filter too.
 

Zephyr7

Registered
Coolant tester is something like this:
https://www.amazon.com/Antifreeze-R...teway&sprefix=coolant+refr&sr=8-2-spons&psc=1

I haven’t used that particular one, it’s just one of the first ones that came up on amazon. Note that it can’t really tell you much about corrosion inhibitor content, that would take a lab test. The Refractometer checks the freezing point of the coolant mix. As I understand things, corrosion inhibitors should normally last at least 5 years in a sealed system. There are glycol lab places that you can send a sample to for analysis if you really need to play it safe.

I’m just doing 5 year scheduled coolant changes, with a full flush and fill (using the coolant flush stuff) each time. Inside of the block cooling passages look great. My 20RZ gensets are around 30 years old now.

Bill
 

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