Wednesday, 6 August 2014

Diesel engine oil pressure

Why does it matter? How much do you need?


This month we went to a call out where a healthy motor dropped oil pressure for no reason. The motor was fine when stone cold but as soon as the oil warmed up the pressure dropped out to around 5 psi. We started with a simple fix of checking relief valve inspection but all was good there so we had to check the bottom end of the motor.


The big ends and mains were in good condition and they didn’t really explain a drop in oil pressure so we kept digging and found that a piston cooling nozzle had come adrift. We replaced them as a set and gave the motor some bearings and rings while we had it apart.

We then re assembled the engine and found the oil pressure restored to 40 psi at idle. The motor has been running perfectly now for a couple of weeks.


Diesel engines like good oil pressure to protect moving parts that are under high stress.


This navara engine seized after the sump got staked and ran the engine dry.



Wednesday, 8 January 2014


What are you getting for your money with a pre trip inspection? What are good mechanics on the look out for to ensure your 4WD makes it through that big trip?

A pre trip inspection should take around an hour and we always start with the radiators and cooling system. Modern 4WD’s can have transmission coolers, a/c condensers and intercoolers that can have bugs and all sorts of muck that can impede flow to the radiator. We had a couple of cruisers that got blocked that bad we had to remove the coolers individually and unblock them with a gurney and compressed air. Also check the coolant is in good condition and not water diluted and contaminated with rust or oil.


Every pre trip inspection should include an electrical assessment of the charging system. You don’t need to be an auto electrician to clean battery terminals and top it up with water but any parasitic drains or bad charge rates need to be sorted. Any new equipment (i.e. Fridge, Spotlights etc) needs to be locally tested before getting into a remote area and realising the alternator isn’t up to the job. Water, salt, dirt and electrical currents all give your connections a very hard time and regular maintenance is required. If wiring up your own accessories make strong water proof connections. There are a variety of contact cleaners available. I prefer WD40 or CRC5.56 together with a light scrubbing of the dirty connections with sandpaper.


Wheel bearing maintenance is critical for your own safety and good reliability. Most manufacturers recommend 100000km service interval for replacement but heavy off road driving demands this interval be shortened. It is important to inspect brakes as well as suspension components when you have the bearing assembly apart. There are a number of different greases available and you have got to be certain that you use a high speed bearing grease. If you are unsure just get down to your local bearing and industrial supplier and they will give you the right one. They also make good bearing packs and can sell any belts and seals you might need. The vehicle should be jacked up and checked for smoothness and good adjustment. Also give your ball joints a good shake and change them as required.

Left to right CV Joint Grease, Purple high tack bearing grease (what we use), Valvoline and Mobile blue grease(high speed bearing) Extreme high pressure grease for earth moving.


Many 4WD’s go through two or three gearboxes compared to maybe one motor. Lack of care/leaks and bad oil are the number one killer of boxes. In their operation they generate metal and that needs to be drained and refilled with good quality oil at regular intervals. Upgrades like oil saver hoses on the cruisers can save money long term if you have a failure with your gearbox output shaft seal. Transfer case oils get a lot of steel and heat and need to be kept in good condition. If you drain out a lot of steel it is cheaper to get it repaired sooner rather than later when more serious damage occurs. Most reconditioners charge extra if the core return has a hole in the side it.

Gearbox and transmission oils in 20l packs. These containers could do 2 major drive line services on this cruiser.


Diesel engines need good servicing or their life will be reduced. Regular oil and filter changes are really important and also don’t forget about timing belt intervals. Any smoke needs to be looked at and there are three different types that diesel mechanics look out for.

White Smoke – This generally indicates partially burnt fuel or coolant getting into the combustion chamber via the head gasket (also check air cleaner after a dusty trip). Also with 1HZ motors when you have white smoke on a cold start up and it clears up you know straight away that you have glow plug issues. 1HZ motors are indirect injected and rely heavily on glow plugs for starting. If the motor won’t fire up straight away don’t burn out your starter because they can crank over all day and not start with out plugs. If you get caught out in the bush with a glow plug wire fault under the dash somewhere you can use a jumper wire from the battery straight on to the glow plug and be able to get home. Bad fuel can also give you a white smoke if it doesn’t stop a diesel motor. It is important to drain your fuel water separator regularly and use some diesel conditioner if fuelling up out of drums in remote areas.

Blue Smoke – This generally indicates oil burning and means rings or a turbo seal are faulty. When you get a seized piston you get a combination of white and blue as the seal on the bore is that bad there is a lot of oil as well as not enough compression to burn the fuel.

Black Smoke – This generally indicates over fuelling or a bit of injector dribble. In this condition the fuel is completely intact as opposed to white smoke which is partially burnt and is doing no useful work.

This 1HZ has an aftermarket turbo and 300 000 kms on the clock. It is well looked after and doesn’t smoke or leak.

Will my older 4WD make it on that big trip?

Older style diesels are tough they can take some bad fuel and you don’t need a scanner or expensive diagnostic equipment to tackle a fault. If they are well looked after they can be just as reliable as their newer counterparts. They have heavy duty rugged motors in them and parts are readily available and as well as cheap. If you have a mechanical problem just some common sense and basic knowledge will get you on your way. I recommend an older style 4WD for DIY mechanics and people on a tight budget. Pajeros and Jackaroos are good capable off roaders and can found cheap on the second hand market. Landcruisers and hiluxes hold their value and are great 4WD’s.They are a bit more crude but if you do break something on them you don’t have to take out a second mortgage to fix it.

Enjoy your 4WD and keep safe 

Head Mechanic 
Express Diesel Service

Express Diesel Service offers extensive pre-trip servicing. Check the website for our contact details.



Monday, 2 December 2013

What we've been up to lately ...

Trencher crack and final drive repair

This trenching machine hit some hard ground and damaged the chain drive and also cracked the bracket that holds the lift cylinder on. This job took us a few days as we started at one end of the machine and finished at the other. We ground out the cracked weld and used a vertical up weld with the mig using about 350 amps. We pulled the final drive down and repaired the damaged shaft in house. Just when we thought all was well with the trencher the coolant was contaminated with engine oil. We thought the oil cooler was a suspect with the Cummins diesel so we removed it and it was found to have a pin hole leak. We gave the motor a good service and the machine was back out digging after 3 days.

Scania engine change out 

We had a look at a truck with major engine damage. First we removed the heads and found quite extensive damage to the liners and also the block. The engine was cooked and the pistons had welded themselves to the block! We sourced a second hand motor for the client and when installing we found the radiator was completely blocked.  A radiator specialist tried to clear it but couldn't so we sourced a new one from Scania. This job was completed in a weekend.


Land cruiser Transfer case rebuild  

This transfer case was found to be generating metal when we were doing a service. One of the thrust washers was worn and we replaced it and put it back together with out having to replace any major parts just seals and gaskets. Also we changed all the fluids on the cruiser and repacked the cv joints and hub seals. This 75 series is a working ute and carries a lot of gear so the owner didn’t mind us using the best oils and coolant as it saves him money in the long run. We used a synthetic gear oil in the box and  transfer case to give the best possible protection. It makes the gearbox shift a bit harder on a really cold morning but with all the towing the owner does he doesn’t mind as the oil heats up pretty quickly. We have found synthetic 90 weight oil the best in these cruisers. We tried 85/140 but the shifting was way too difficult.

Remote area truck repair  

This Iveco had a sticking compressor valve and just wouldn't build up air. The client couldn't get to his job so we drove through the night and fitted a new compressor out in the bush. This truck is a real work horse and we since have been looking after it. We also changed out the Road Ranger gear box and the water pump.

 Any questions? Please comment or give us a call any time!

Sam Gray
Head Mechanic
Express Diesel Service