Community Forums

DurangoNick · 09-11-2019, 04:20 PM

According to the manual for my Onan 5.5HGJAB-1038K, I am suppose to adjust the valve lash at 500hrs and clean or replace the cylinder heads at 450hrs. As I am now at 483 hrs, these are looking right at me. Questions:

1 Is it really a good thing to do these?
2 Any estimate as to cost?
3 We live in our coach. Any estimate on how long they'll want it?

I did do my best searching on the forum, but was unsuccessful in finding an answer.

Thanks.

Redapple · 09-11-2019, 09:51 PM

I did the valve adjustment recently. Mine was at about 365 hours. Lash was way out. I would recommend doing the valve adjustment. I highly doubt people are changing the heads because the manual says so. Unless you have a real reason do the valve lash adjustment, check for anything obvious such as leaks, warping. Cracks e.t.c, and call it a day.

I did a major sercice on mine. Valve adjustment, oil, filter, air filter, fuel filter. fuel pump and spark plugs. Runs great.

Good Luck

DurangoNick · 09-12-2019, 07:39 AM

Quote:

Originally Posted by Redapple

I did the valve adjustment recently. Mine was at about 365 hours. Lash was way out. I would recommend doing the valve adjustment. I highly doubt people are changing the heads because the manual says so. Unless you have a real reason do the valve lash adjustment, check for anything obvious such as leaks, warping. Cracks e.t.c, and call it a day.

I did a major sercice on mine. Valve adjustment, oil, filter, air filter, fuel filter. fuel pump and spark plugs. Runs great.

Good Luck

Thanks. I do the other stuff myself per schedule. It was the valves and particularly cylinder haeds that would be beyond me. I use to adjust the valves in my Triumph sports car, but I don't even know where they are on this thing :-) I'd love a YouTube video on that...

RRR · 09-12-2019, 11:09 AM

I did some research on my 5.5 HGJAB Spec K and never found any real conclusive information on the head replacement. Couple of things I found was run Seafoam through it for 20 (?) minuets under a half load along with the valve adjustment. Couple of others said don't bother with the head. So who knows?

I was ready to do mine but got up to my neck in a problem with the S&B so it is kinda on the back burner.

Redapple · 09-12-2019, 07:21 PM

I just looked at the service manual. At 450 hours it simply say clean ore replace heads, with a subscript that says experienced Onan technician. The heads on my genny looked fine so I just adjusted the valves.

Valve adjustment is easy and I am happy to send you the procedure from the service manual. Took me about 30 minutes.

DurangoNick · 09-13-2019, 03:29 AM

Quote:

Originally Posted by Redapple

I just looked at the service manual. At 450 hours it simply say clean ore replace heads, with a subscript that says experienced Onan technician. The heads on my genny looked fine so I just adjusted the valves.

Valve adjustment is easy and I am happy to send you the procedure from the service manual. Took me about 30 minutes.

That would be great. true_dog@hotmail.com.

Thank you!

twinboat · 09-13-2019, 03:38 AM

The cylinder head cleaning is to remove carbon buildup from the combustion chamber.

When carbon builds up, it creates hot spots, clearance issues and higher compression. The hot spots can cause pre-ignition which can be damaging.

Is this a critical issue, I don't think so, and misting the intake with sea foam or water at high RPMs claims to break the carbon deposits up.