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The resurrection of an Onan 6.5 NH-3CR/16004P


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  #1  
Old 12-27-2015, 11:43:02 PM
JohnnyC JohnnyC is offline
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Default The resurrection of an Onan 6.5 NH-3CR/16004P

The resurrection of an Onan 6.5 NH-3CR/16004P, serial # A863977927 built in January 1986.

This genset lived its hard life in an ABC News van for many years. Obviously it was taken out of service, but I don’t know exactly when and how long it was left sitting unused. I bought it on Craigslist in late December 2015. The seller does not know much of it past life time and bought it for his food van, but the 6.5 NH was too big and heavy. He bought a lightweight Chinajunkerator instead.

I had my eye on this 6.5 NH for weeks and after I noticed it was not selling like many of the other generators in my area, I called the seller with a super lowball offer and told him I have cash in hand and ready to pick it up NOW. He agreed and I got it since he wanted it gone to make room in his garage (it pays to wait sometimes then strike with a super low-ball offer with the understanding you WILL pick it up upon hanging up the phone).

This 6.5 NH was very dirty and greasy, but totally complete from A to Z. When I got it home, I hooked up a battery and immediately got it going on engine starting fluid. Spritzing the starting fluid kept the motor going, so I hooked up a gas tank and the 6.5NH ran great and produced voltage. The only problem I know of is the carburetor. I have to keep the choke 7/8 closed for the motor to run silky smooth. Obviously the carburetor will need to be rebuilt. That is small beans compared to what I could have discovered with an untested old genset.

Although I got this genset to run without any effort, it is far from being 100% reliable in my book. I hope to someday make this genset look and be mechanically like new. In this thread I will post updates and pictures throughout the resurrection of this Onan just as I did when I refurbished a 5.0CCK and my 15.0JC. Input from members will be greatly appreciated when I run into problems or when sharing ideas. Maybe the information in this thread will help a future generation of restorers after we are gone.

To start:
As already stated, I got the 6.5NH to start and run although the carburetor needs to be rebuilt.

Today’s work:

1) I gave it a complete bath. The genset was very, very, very dirty. The oil and dirt was very thick on top and below the genset. I have no idea what caused such a leak on top of the genset, so I will observe for leaks during the next few test runs now that it is clean and any leaks will be easily seen. So far I noticed no leaks and all seemed well.

2) I drained and refilled the oil with fresh 10W-30 and replaced the filter with a FRAM PH3600. I will let the new oil run through the genset as a “flush” for about 10 hours of periodic use then refill with full synthetic oil and change the filter again.

3) I did a compression check. I get 125 p.s.i. in the right cylinder and 120 p.s.i. in the left cylinder.

In the pictures below, it shows the genset as I got it and after today’s bath. Although I gave it a bath, I can see only 90% of the dirt was removed. The 10% that remains will be cleaned as I tear down the genset.
What is my next task? I think I’ll make a parts list of things to buy such as gaskets and work on the carburetor.

That’s it for now…
JohnnyC
New Jersey
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  #2  
Old 12-27-2015, 11:51:33 PM
nothingbutdarts nothingbutdarts is online now
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

I believe I have read on here that your style 6.5NH can have issues with the two piece intake manifold having a vacuum leak. While you have it apart refurbishing it you might look the intake over closely for any leaks or reseal it as some member here have done.
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Old 12-28-2015, 12:10:32 AM
JohnnyC JohnnyC is offline
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

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Originally Posted by nothingbutdarts View Post
I believe I have read on here that your style 6.5NH can have issues with the two piece intake manifold having a vacuum leak. While you have it apart refurbishing it you might look the intake over closely for any leaks or reseal it as some member here have done.
Many thanks for the information! Much appreciated. This may be a good clue why the intake manifold (and carburetor) is painted a dark green. Without doubt they were removed for one reason or another. Maybe this genset experienced the know issue you pointed out and while the intake was removed along with the carburetor they were repainted. All else looks to be untouched and original including the spark plug wires.


JohnnyC
New Jersey

---------- Post added at 11:10 PM ---------- Previous post was at 11:06 PM ----------

The following link is a short video on the first startup on gasoline that I shot yesterday after unloading it from my trailer.

https://www.youtube.com/watch?v=TcIjPwxJZCA

JohnnyC
New Jersey
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Old 12-28-2015, 12:35:20 AM
YellowLister YellowLister is online now
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

that bottom oil pan gasket leaks as you can see.. common issue with these. mine does as well.

yours looks like it had a good leak from the points box and or governor shaft. does it have any play in it?

hows the carburetor butterfly shaft play?
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Old 12-28-2015, 01:15:52 AM
JohnnyC JohnnyC is offline
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

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Originally Posted by yellowlister View Post
that bottom oil pan gasket leaks as you can see.. common issue with these. mine does as well.

yours looks like it had a good leak from the points box and or governor shaft. does it have any play in it?

hows the carburetor butterfly shaft play?
I kind of suspected there may be oil leak(s) in the oil pan gasket. I will check all the areas you mentioned. It should be easy to spot any oil leaks now that all the old oil and crud was removed.

What material is used for the oil pan gasket? If cork is used, I will use RTV instead. I never had good luck with cork based gaskets. If you slightly over tighten the bolts and the cork is too compressed, it will leak. Old cork gaskets seem to get brittle and split easy and once there is a leak, you can't stop it without replacing the entire gasket.

I guess I will add these gaskets to my list. I rather change everything now rather than painting the genset and finding oil leaks afterwards.

Oh, I reading the parts manual. It appears the original head gaskets may have had asbestos in the material used for the gaskets. What are they made of now?

JohnnyC
New Jersey
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Old 12-28-2015, 01:54:47 AM
YellowLister YellowLister is online now
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

there a hard paper gasket.. have you ever heard of curil k2 sealer? its very popular with the air cooled vw engine builders, even Vw uses it at the factory.. ive used it myself this last year its great stuff, for when you put it back together..

http://onanparts.com/index.php?main_...roducts_id=327

oil pan gasket.. gasket sealer

http://www.ebay.com/itm/New-Elring-S...FWeb9Y&vxp=mtr
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Old 12-28-2015, 02:24:37 AM
JohnnyC JohnnyC is offline
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

Thanks Yellowlister for the gasket part number. It is on my list and will order through Onanparts.com as I did in the past. Onanparts.com exceeded my expectations on my last order for my CCK. I used many different sealers in the past. Some with good results and others with bad results. What I learned is to make sure the metal surfaces that make contact with the gaskets are totally clean and defect free for the best seal along with proper torque and tightening sequence.

I been poking around on the internet and this site for Onan 6.5 NH oil leaks. There are many reasons for oil leaks. One hit that I found using google states that if the breather is clogged or excessive crankcase pressure builds up, leaks can occur. I will check the breather. Additionally, I will run the genset under a load for an hour or two and look for leaks. Right now gasoline is cheap. 3 gallons will allow this gen set run for about two hours under moderate load.

I read about a neat trick using white baby powder spinkled on areas where suspect leaks occur. The white powder will stand out to be easily seen if oil comes in contact with it. I might give that a shot.

Thanks,
JohnnyC
New Jersey

---------- Post added at 01:24 AM ---------- Previous post was at 01:17 AM ----------

One last thing that I recently read on a different site (an RV forum site) where a poster stated that he has 120 psi in his 6.5 NH cylinders (same reading as mine -> 120/125). Someone replied that is not good, but will not stop the genset from running.

I have not seen what is good and what is not for a 6.5 NH in the few manuals I have for the 6.5NH spec P, but for a 5.0 CCK with low compression heads, 120 psi is perfectly acceptable.

Do you know offhand what the specs call for in regards to compression for a 6.5NH and what manual it is found in?

Thanks,
JohnnyC
New Jersey
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Old 12-28-2015, 03:45:42 AM
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

"What material is used for the oil pan gasket? If cork is used, I will use RTV instead. I never had good luck with cork based gaskets. If you slightly over tighten the bolts and the cork is too compressed, it will leak. Old cork gaskets seem to get brittle and split easy and once there is a leak, you can't stop it without replacing the entire gasket."

The two-piece sumps all seem to ooze oil from between the steel pan and the cast sump. That's the advantage of having the earlier one-piece oil sump: No leaks.
The advantage of having the two-piece sump is ease of removing and cleaning the pan. It can be removed and cleaned much more easily than the one-piece sump.
To remove the one-piece sump, the unit must be raised enough to clear the oil pickup tube/screen, and it goes to the very bottom of the sump, which means you have to lift it WAY up to get it off.
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Old 12-28-2015, 08:11:41 AM
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

Johnny,

According to the NH engine manual, compression should be between 100-120, so you're fine.

I'd also like to affirm two earlier observations: check the intake carefully for cracks/leaks, as that could cause the lean running; and a clogged crankcase vent could force oil out of places that wouldn't normally leak.

Jim T.
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Old 12-28-2015, 08:41:43 AM
JohnnyC JohnnyC is offline
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Default Re: The resurrection of an Onan 6.5 NH-3CR/16004P

Quote:
Originally Posted by lokay5 View Post
"What material is used for the oil pan gasket? If cork is used, I will use RTV instead. I never had good luck with cork based gaskets. If you slightly over tighten the bolts and the cork is too compressed, it will leak. Old cork gaskets seem to get brittle and split easy and once there is a leak, you can't stop it without replacing the entire gasket."

The two-piece sumps all seem to ooze oil from between the steel pan and the cast sump. That's the advantage of having the earlier one-piece oil sump: No leaks.
The advantage of having the two-piece sump is ease of removing and cleaning the pan. It can be removed and cleaned much more easily than the one-piece sump.
To remove the one-piece sump, the unit must be raised enough to clear the oil pickup tube/screen, and it goes to the very bottom of the sump, which means you have to lift it WAY up to get it off.
Thanks Lokay5. Since this thing is old and has time on it, dropping the oil pan to clean all crud is welcomed by me. I will seal it up so it will never leak afterward.

JohnnyC
New Jersey

Quote:
Originally Posted by b74eqcm View Post
Johnny,

According to the NH engine manual, compression should be between 100-120, so you're fine.

I'd also like to affirm two earlier observations: check the intake carefully for cracks/leaks, as that could cause the lean running; and a clogged crankcase vent could force oil out of places that wouldn't normally leak.

Jim T.
Thanks Jim... I thought 120 psi was good. Not sure why someone posted it was not, but it was an RV site with a majority of posts on other RV subjects. I assume the poster was not a knowledgeable Onan person, just someone that wanted to be heard.

JohnnyC
New Jersey
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