1991 GQ 4.2 diesel Questions

[Zantus]

Hi Guys

I have a few questions about a 1991 GQ 4.2 diesel.

If it has manual windows, no plastic wheel arches and manual mirrors, what would the model designation be? I only know the SGL models, what are the base models called?

How common are these particular models in South Africa?

Driving at below 1000rpm the whole car vibrates. Is that a normal thing or is there perhaps a worn mounting somewhere I can look out for?

What do these generally go for? (350K on the clock, basically standard, interior and drivetrain seems quite good, but body had some rust repair and it was a bit of a rough job)

[ricster]

I know Grant on the forum has a 1995 GQ 4.2 diesel that's called a Patrol ST. His if I'm not mistaken did not come out with all the luxury extras like the cooler in the back etc. So this might be the model type like yours, just a few years older. Andre ( Stefaansie ) has the SGL-D which is the 1996 model, but I think his came out with all the extras.

Hopefully some of the GQ guru's will be able to assist or correct me. Does yours have a turbo, or is it normally aspirated? What colour is the tappet cover. You may just be the luckiest chap in town with the old school "silver top" TD42. Also check it there is a ( I think) vacuum pump on the back of the alternator.

[Zantus]

Well, I had a look and it does have a silver tappit cover that looks original and a vacuum pump on the back of the alternator

I took delivery yesterday, but I'm waiting for the bank transfer to go through and the paper work to be done before I get stuck into fixing things. I love my 4.5GRX, but this old has a whole different charm to it and drives like a dream.

It also struggles to shut off after driving, i.e. the engine keeps on running, albeit very slowly, even after the key is removed

[ricster]

You lucky ...... fella....hahaha. You have the best TD42 engine EVER produced. That motor can handle a turbo with rather high boost faaaaaaaar better than the later model TD42's like mine. You scored !!!

The continued running after shutdown is the residual oil or diesel that's still in the chambers. Depending on the condition of the engine, I would think that there might be oil passing through the rings, or through the valve stems, or more likely is that oil or a heavy oil vapour is passing through from the tappet cover breather back into the air inlet manifold. This could become a catastrophic problem as you could land up with a run-away engine that will get to a point of over-reving as oil vapour is constantly being fed into the chamber with no way to shut it off other than blowing up the engine..... not advisable....haha.

The oil vapour is probably caused by the combustion chamber air bypassing the rings, and pressurizing the sump and the pressurized air then travels up to the top of the head into the cavity of the tappet cover and is pressed out through the speaker magnet looking thing ( breather ) near the no 6 piston. there is then a pipe that connects again into the fresh air inlet pipe feeding into the inlet manifold. If you have a turbo on there, your turbo vanes will be heavily coated in oil. Although a VERY little oil is not a problem on the turbo vanes. Lots of oil can, in my opinion, be a catastrophic problem.

[ricster]

If it was mine.... wish it was..... I would take the motor out, and take it apart. The combustion chambers will show cracks on them. Don't worry too much about that .... they all crack. As long as the head is not cracked, which I seriously doubt as you did not mention anything about overheating.

Things I would replace:
1) injectors - unless you know that they have been replaced recently ( was told injectors last about 70 000km ) They cast about R 450 each to recondition.
2) Piston rings. Here you use the Nissan 2.7 diesel rings. (Tour de Frans) Frans will hopefully correct me if I'm wrong. These are identical to the 4.2 and are lots cheaper!!
3) All bearings - big ends, crank shaft the whole lot. Check the size of the gudgeon pins as yours will probably be bigger than the ones on my TD42.
4) GENUINE Nissan headgasket. These motors push out a compression ratio of 22:1. Frans gave me this advice and I trust his advice and its worked for me !!
5) Gasket set - This will work for all the other stuff, but not the rear crank shaft seal. Either use a genuine Nissan part or you can modify the casing of the existing, and insert the gasket set supplied seal.
6) Check the old head bolts for stretch - replace if necessary - I bought genuine Nissan head bolts for mine. I didn't want to take a chance ( you will see when you have to torque down the head ..... eat lots of strength food)
7) Radiator antifreeze/coolant - Again of Frans recommendation - I used GENUINE Nissan Antifreeze, cost a lot as I needed 6 bottles ( the TD42 system takes I thing 13 odd litres of water) DON'T USE CHEAP ANTIFREEZE/COOLANT.

Things to check:

1) Flush out the radiator
2) Check the clutch and thrust washer while the engine is out.... trust me its friggin heavy
3) All belts
4) Glow plugs - Connect to a battery and see if they glow red almost instantly. Replace if necessary from local spares shop. NGK work great in mine.
5) Oil pick up that sits in the sump - give a good clean and ensure its in good condition.

Things to do after its rebuilt. Send it to a GOOD dyno place to set up the pump timing perfectly.

I think, but may be a bit out, you could do all this yourself for way under R 10 000. And you will have a BRAND NEW TD42 silvertop.

Here is a link to my rebuild to give you an idea..... I had also NEVER opened a motor of this magnitude before in my life.... but I did it.... It was a little dirty at times, but was brilliant sense of achievement !!

[Stefaansie]

Hi Zantus,

As Rickey said, I've got the SGL model, met climate control nogals.

Ek wonder of jy nie die Safari het nie.

Anyways,

Die vibrasie onder 1000rpm is ek nie slim genoeg om jou te antwoord nie. Myne doen dit ook. Ek wonder of dit dalk te doen het met timing, of daai helse fly wheel.

Vertel ons bietjie meer van daai lorrie van jou.

[Zantus]

Ok, just picked up the registration papers so I guess I can call it mine now. Will post some pics when I get a chance to download them off my phone.

Unfortunately I don't intend to spend big money on it. I was in a position to help someone out who was in a dire financial situation and I bought not having much knowledge of what it actually is or what it is really worth, but I did know in whatever form it comes, the 4.2 diesel is the pick of the bunch.

I think the vibration might be an engine mount as I see some metal on metal contact on the passenger side mount and the vibration is very similar to a vibration I had on my old 240D merc when an engine mount collapsed.

I've only driven it around town for about 150km's, but it was around 30 degrees the past two days and there's definately no overheating. Also, a friend of mine drove behind me when we picked it up and there was no noticible smoke, so I would rather try and find the problem first before going for an engine rebuild. She is just run in now...clocked over to 350 000km's yesterday

The old girl is quickly growing on me, so I don't think I will be turning it into a quick flip as I originally planned and I hope I can keep her for a while

[ricster]

Is it a turbo??

Then as for the runaway after switching off, I'm a bit stumped.... I may be way off here, but could it be a carbon buildup in the chamber that is glowing from driving, or soaked in diesel and still igniting when under pressure?? Hopefully someone can answer that. I would fill up the 90L tank and dump in 500ml of MARINE 2 stroke oil, and give it a good drive to burn out the carbon deposits. If you don't want to fill up then 45L to 250ml MARINE 2 stroke oil etc. I think that that will help. You could probably add a little more 2 stroke to the diesel for the first time, as it cannot do any harm, other than give you a smokey rear end.

As for runnin in.... yip you are spot on. If that motor has been looked after (serviced EVERY 5000Km ) then that motor is sweet and bulletproof !! I'd say you got a good deal... would love to know what you paid for that beauty, but know never to ask a womans age.....hahaha... Well done on owning a great Patrol

[Zantus]

Sorry, it is a non turbo.

[ricster]

That is even better news. That motor should still be strong, so not too sure about the continuous running after shut off thing.... Lets hear what the other guys say.

PS Welcome to the "Real trucks don't have spark plugs" gang.......hahahahaha