Thread: Hitachi ditch the 4HK1 for the 6BG1T.

Off-highway emissions specs are several years behind on-highway.

I suspect the change may be due to the issues with injector and pump life on CR diesels operating in extremely dirty environments.

The 4H? also have problems with spinning main bearings and not being repairable - they don't have separate caps for the mains, but a one piece 'cradle' arrangement.

I did see a mention of a 4h spinning mains along with a fix.The main bearing support system makes a pretty strong bottem end and as have not seen it mentioned other than that post I wondered if it was a one off I intend to test it to its limits so time will tell

Originally Posted by Ancient Mariner

I did see a mention of a 4h spinning mains along with a fix.The main bearing support system makes a pretty strong bottem end and as have not seen it mentioned other than that post I wondered if it was a one off I intend to test it to its limits so time will tell

I'm only going from what I have read, not experience, with these engines. The following quotes are some I found quickly, and all but the 2nd are from a brisbane mechanic how works on these.

Any 4H or 6H engine that has spun the main bearing shells are a throw away Yes I have the ovesize bearings to accomodate the rebored tunnel but when the tunnel is damaged there is no other repair other than metal spraying the tunnel and resizing to standard size.
The oil pump is meshed to the crankshaft and is fitted between the upper and lower block sections and the lower half can not be surfaced and the tunnels resized as the pump gears will not realign with their bearing locations.
Cylinder heads are in the same boat when the engine has an overheat problem the cylinder heads bend and distort and the cam shaft tunnel is then misalined and bearing bind then is a problem as well as the cam drive gear mesh with the idler drive gear.
There are thicker head gaskets available but in most cases they are not able to overcome these problems
Bob

I purchased a bad 99 Isuzu 4.8 engine with A450 to use for mockup in a conversion (and spare parts down the road) while searching for a good low mile one. The engine I purchased has a spun main, but I haven't torn it down to fully inspect yet.

Spun #3 and 4 main bearings seem very common in the early 98-00 4HE1 engines. Reading on this site and others some have linked these bearing problems with the oil filter system these early engines used combined with not enough oil changes. Is this accurate? Did Isuzu change the oil filter setup on the later engines? If so, when did this change occur?

When the main bearings spin in a traditional engine the caps are cut and the main line is honed back to size/alignment. From the reading I've done the 4HE1 cannot be repaired this way as material cannot be milled from the mating surfaces of the upper or lower block as a change in crank centerline will be a problem for the engine's geartrain and oil pump. Am I understanding this correctly?

There was mention of oversize main bearings to allow honing of the main line. I couldn't find the source, just mention they were available. Can anyone elaborate on a source for these and how much oversize they can accomodate?

Hi, I have only just logged on and I noticed that astr's question on the oil pressure of his 4HE1 engine has attracted some coment. Let me say firstly I am a mechanic and work on these engines. He said that his oil filter has 2 filters in the filter can.This is the old type of filter the newer type is full flow only and will overcome the high pressure and bearing problem.Secondly if the bearings turn then the block may have to be scraped, however I have had made for me, oversize bearings to repair the damaged tunnel.The bearings are available from me at a cost of $200.00 AU plus postage each journal.I hope this may help .

astra, Check the oilfilter housing to block face, there are normally 'o' rings that seal the passageways. If a gasket is used to replace the 'o' rings the small hole that is the bypass passage for the filter may be blocked. This will definitely make the pressure go through the roof.The Isuzu filter kit part No 92955808 has the latest type filter.I dont thimk that the turbo oil feed will cause a problem provided nobody has interfied with the turbo oil circuit.Is the turbo wheel and shaft within spec and does not have excessive clearance

astra, The only other area to check unfortunately is the oil pump where the relief valve is located. Has No3 main bearing spun? of all the engines that I have seen No3&4 journals are the ones that have been damaged. It is not only 4HE1 tc engines that damage these journals all 4H engines damage these journals especially if the oil is not kept in good condition.

astra, I am of the understanding that the oil flow was significantly impaired with the dual filter, hence the reason Isuzu have gone to the full flow only. Even the 6HK engines have gone to the full flow, and by the way ,the long filter fitted to the 6HK engine will screw onto your housing provided you have the room it is twice as long in length. In these modern engines the flow of oil is more critical than pressure, provided the flow is maintained the oil additives will do their job.If you drop the pan you will not see much as the lower case doesn't let you.

I am at present working on a 4HF1 and you wouldn't believe how much damage this guy has done 4 out of the 5 main bearings have spun which has been caused by him not changing the oil more regularily.Especially as the engine has done 600k and he does constant stop start deliveries and idleing to keep the air con going.Although I have the oversize bearings to repair the tunnels I think that this one has gone that bit too far. The centre main has actually split in half and and a slug of metal was jamed in the oil hole.I'll photo it and post them.
Bob

The operator I spoke too hasn't had any bearing problems. But they did have a warranty job on the head very soon after purchase. Head not torqued at the factory apparently.