The Cummins 5HDKBB 10,000 Hour Service

Cummins 5HDKBB

A Cummins 5HDKBB on the bench

A 10,000 hour service might not sound a lot. The standard calculation to convert hours into miles on static engines is to multiply the hours x 40.

When you put 10,000 hours into miles the calculation is 400,000 miles, we are getting close to ½ million miles.

What I am about to do is give you an idea of what is involved in a 10,000 hour service.  This article is only a guide, so I am not looking for any court cases!

As you can see from the periodic maintenance sheet, it gives certain things to check every 1,000 hours, as well as showing in the bottom column a timescale.  If you have serviced your generator correctly, you would have been changing the water pump belt and adjusting your valve clearances every 1,000 hours.  If the engine oil and filters are changed at the correct intervals then the generator should be running nicely, I have seen them still operating with 18,000 hours on the clock which is equivalent to 720,000 miles.  The engine oil and filter, fuel and air filter would need changing as well as valve clearances and the water pump belt.  All of this would be done as part of your routine 1,000 hour service.  What we need to do now is examine some of the other operations mentioned on the sheet.

The service schedule


Flush the Coolant System

Anti-freeze not only stops water freezing, it also contains a corrosion inhibitor which reduces not only corrosion but air bubbles being formed by the water pump.  These air bubbles can eat away at the engine cylinder bores and in severe cases can make holes in the cylinders (Toroidal cavitation).  My advice is, if the coolant has not been changed before then, now is the time.

The water pump has no tensioner and that is why it needs changing every 1,000 hours (40,000 miles).

Replace the Coolant Pressure Cap

If the seal is okay and the cap blows off at the correct pressure then I might just ignore this one.

The water pump

Replace the Coolant Hoses and Thermostat

Oil leaks are the main culprits for deteriorated water hoses, this is because the oil makes them go sticky.  If the hoses are in good condition then I would leave them, the same applies to the thermostat, although if you have had overheat problems then yes you would have to replace it.

Service Fuel Injectors

At 400,000 miles you should change the injectors because an internally leaking injector can burn holes in a piston.  As the injectors are quite expensive, you may be able to leave them a bit longer if they are not causing the engine to black or white smoke.

Check Generator Bearings, Drive Belt, Belt Tensioner and Drive Coupling

A close up of the damper

A close up of the damper

This is a picture of what they are listing.  The engine on the left drives the generator on the right via a drive belt with a belt tensioner in the centre.  Expensive?  Yes, you might be tempted to skip this one. No, definitely not a good idea.  The 5HDKBB has a two cylinder engine that drives the generator, for those that have had a two-cylinder motorbike will know that it is not one of the smoothest. On the left of the picture is the dark object that the belt goes round, this is a metalastic rubber drive.  Its job is to absorb the shocks and imbalances of the two cylinder engine.  This metalastic damper is prone to breaking up not long after the 10,000-hour service interval.  The drive belt will need changing as it will be cracked.  Also, the tensioner has a bearing on the wheel of which the belt runs and also contains a spring, to be on the safe side I would change this.

Generator Bearings

On the right-hand side of the picture you have the brown coloured pulley, this is the generator pulley.  The generator shaft is supported by a bearing which is behind the pulley.  If you cannot detect any up and down movement of the pulley when the belt has been removed and if you spin the pulley and it does not make any grinding or rumbling noises, then you could leave it.  The drive beltI would personally change it as I wouldn’t want the down time of the generator if the bearing failed later on.
I hope this article has been some use, as I said before it is only my suggestions and practical thoughts obtained from many years of experience.

If you have a problem with an Onan generator or require any parts for one, contact LAS Motorhomes on 01604 861999, and we will endeavour to help you the best that we can.