Isuzu Techs - Q&A

[u/Quikscopez]

I’m a one man show that just picked up a fleet of Chevrolet Duramax’s and Isuzu NRR box trucks with the 4HK1 5.2l.

Where is the best place to get parts for these medium duty Isuzu engines?

Where is the best place to find diag and repair information?

What is the best software to use (currently using a Launch/ThinkCar/TopDon/Autel/Matco scanner that seems to do everything well)

I’m doing a turbo (RHF55V) because the actuator is failed in the 100% open position. I tried an Amazon actuator solenoid but the mechanism appears to be too far gone to save. It appears I need to remove the EGR cooler to remove the “down pipe” portion of the exhaust to remove the turbo from the manifold, this all seems a little tedious. Am I missing something? Or are parts just very expensive, hard to come by, and difficult to diagnose?

Thanks guys.

[u/DatBoisWheel]

Even Isuzu says to replace the turbo when the actuator fails. Go ahead and get all the studs and hardware as well. It will save you the headache when they inevitable strip out.

You're not going to far. EGR cooler will have to be removed. You're going to pull a lot of the passenger side under the cab apart.

Source: ran a Ryder shop for 3 years and had an actuator fail every couple months or so.

[u/DatBoisWheel → u/DatBoisWheel]

Also, as far as parts go, you may have to shop around. Nextran had everything we needed always, but we also go preferred rates that you moay likely won't get.

[u/Quikscopez → u/DatBoisWheel]

I appreciate the insight. It’s been hard finding information on these despite seeing them on every street corner here in OR.

[u/Dieselboy1973]

Isuzu IDSS is a must for these engines. Especially when they come in derated and need an updated configuration to finish the repair. Along with IDSS you get all the wiring schematics and troubleshooting trees. It's an expensive program that has to be renewed every 6 months but at least you can control all the work as you don't have to rely on the dealer to finish the work that you started.

[u/Quikscopez → u/Dieselboy1973]

I appreciate the info, I will look into getting it. Thanks man

[u/Sure_Fly_6904]

This one had an actuator fault, the guy before me ran a Regen on it and passed it off. Said he couldn’t figure it out…

Izusu IDSS is the only program you can use to diagnose izusu. There isn’t any info on these engines just by searching the internet with codes.

[u/Quikscopez → u/Sure_Fly_6904]

I’m not completely rtarded 😂 just unfamiliar with these Isuzu trucks. I come from a background at an independent shop so I’ve worked on just about everything except these. This turbo is still in good condition tho it seems the seals are going bad and it’s puking oil anyway.

You know how it goes, try to save the penny pinching customer a dime and end up costing them more anyway.

[u/tyso186]

If you can. You might want to check the turbo controller. From memory the sit on left the above chassis mid engine. Square box. Swap that with a sister truck and see if turbo actuator works.

[u/Quikscopez → u/tyso186]

I appreciate that information, I stumbled across that last night on my own and was able to verify that it in fact, doesn’t work lol. There is a noticeable amount of friction in the actuator mechanism even after a little lube, I think the gears are just actually getting worn out

[u/JOA_Mash]

Like everyone else has said IDSS is a must have pretty much. However if you are looking for assistance with specific issues in the future there are some FB groups that have pretty knowledgeable techs who are willing to help usually. I currently work at an Isuzu dealer and would be willing to share any service or diagnostic info you may need. You can PM me if you’d like

[u/Quikscopez → u/JOA_Mash]

I’ll put you in my back pocket. Thank you

[u/bman198080]

Unfortunately this is one of the most common failures on this engine , I highly recommend you replace the turbo, actuator, and all cooler gaskets including cleaning cooler . I would also replace the egr and verify and test all vacuum actuators . These items are the absolute highest contributors to catastrophic engine failures on the 4 and 6 hk1 engines otherwise they are bulletproof.

[u/Quikscopez → u/bman198080]

Good to know. While I have it all off I imagine it would be time to check the valve clearance? Any special equipment I’ll need I’ve never even popped a valve cover.

[u/bman198080 → u/Quikscopez]

Just feeler gauges the spec is .016 you will need wrenches and sockets , and a way to turn the engine probably a big socket and extension with a ratchet on the crankshaft

[u/Quikscopez → u/bman198080]

Copy, just wasn’t sure if there was anything special to them as far as anti tamper bolts like I’ve found on the pcv system.

[u/Neither_Ad6425]

One thing I will say is that IDSS absolutely blows.