Thread: What to look for when buying a used diesel 4x4

Have added this info to another thread but deserves thread of its own I think...people always buying 4wds.

Often get asked to look at diesel 4wds for people, but there are a few things anyone can check to make sure you don't buy a bad one. Here's a brief checklist of key parts in the vehicle to look at when when inspecting it. Pretty much anyone can do this if you know where to look. Main parts to look at are:

* Steering box seals - is there leakage around box at bottom of shaft = WOF issue.
* Radiator - is there brown dirty water and gunk when you run finger round inside cap area = not well maintained. Check radiator hoses aren't crunchy - this is important but easy enough to replace.
* Motor - is it excessively rattly, does it fume alot with oil cap off, and does it blow blue smoke? Bit of blue on start up ok - but not more. Bit of black is just overfuelling, and puffs of white sometimes water in system = not good. Check also for oil leakages round head/block. Track any leakages/oil dripping.
* Fuel pump - check for any leakages around fuel pump - occasionally you can get away with top seals only but usually a major cost to do pump seals.
* Turbo - is it leaking oil round unit (fixable) or is it whining bad when switched off (stuffed) Few seconds faint whine on turn off is ok.
* Check rear main seal where motor bolted to box. Oil sweating normal, but significant wetness/oil leakage is a gearbox off job sometime.
* Feel driveshafts for movement - if sloppy its likely universal joints - easy enough to do. Check front driveshaft for movement too.
* Check for oil leakage around rear diff head = pinion seal and a bigger job to strip down and reset gears.
* Check rear axle seals - some pressed in and a fair bit of time to fix.
* Check CV boots (inner and outer) - each perished one takes 1-2 hours to replace.
* Gearbox - if auto is it smooth or lurchy? If manual is there clutch judder on take off, or clutch slip when booting it at very low revs in 4th, and are changes smooth and not notchy (worn synchro).
* Engage 4wd low range and test it to see it works well without strange noises. Turn some hard lefts and rights to check CVs for clicking = stuffed
* Check electrics - all windows etc - WOF issues
* Does it have Limited slip diff. If keen you can put jack under rear diff and if both wheels spin same way its lsd, and if wheels turn in opposite direction to each other its open diff. Lsd with some Redline Heavy duty Shockproof Gear oil in it is big traction advantage offroad in 4wd models with good lsd like isuzus and safaris.
* Road test - does it have enough power or is it gutless for the model. You can do compression/leakdown test but you can usually tell when compressions b*ggered just by driving them. When driving does it smoke - and what colour. Smooth straight tracking or wheel alignment issues.
* Tyre wear - a big cost with 4x4s. Muds more than half worn are not much use in slippery conditions - ok for summer conditions or on riverbeds.
* Check body panels individually for damages and rust - esp in sills etc
* Check for lifts/mods done with no certification - can be insurance issue.

That's just a few basic checkpoints anyone who is not a mechanic can do when buying a 4x4. And if you check them and vehicle passes, chances are its reasonably sound and you won't be hit with big bills. If you are still in doubt get a mechanic to test it - better to spend $50 and save $1000s. There will always be some areas needing attention on an older 4x4 - like CVs or steering box seals or something - and that's where you adjust the price accordingly.

Hope this is useful - kind of question that comes up alot. These are things I look at but maybe we could get a few mechanics here to add to/adjust the points above, and then when we've got a good simple checklist it can be a sticky that anyone can print off when going to check your potential 4wd buy. Alot of people buy on the road drive or the look or the feel of the truck and that is not too wise with older 4x4s. A good check can save alot of nasty surprises

Cheers Mike

Excellent post!

Very useful!

Thanks for taking the time to put this together. Maybe it could become a ‘sticky’

Don't know how to make stickies!

I think using your ears is v important when road testing too. Mudgrip tyres will always hum, but beyond that good to listen for wheel bearings - kind of a groink groink at 30-40k. Also listen at 70-100ks for diff whine, and humming noises which can be driveshaft UJs or shaft centre bearing in LWBs. Unusual vibrations can also be driveshaft.

A checklist can save heaps. For example we recently looked at a 96 Wizard advertised as quite good nick. Motor and box were quite ok but alot of other bits b*ggered. On checking the thing it was clear no-one had done proper maintenance on it for years. Our estimate $4000 to put new tyres on it and fix up all the worn/noisy bits/leaking bits - almost as much as the purchase price! Someone else bought it - ouch!!

Remember to take a little torch with you to check bits. Not a maxtoch which will leave you blind for the next 20 minutes........

Another thing is to check the wiring between speedo sensor and speedo for evidence of it having being disconnected (no dirt around plug areas etc) or a switch having been installed. But I imagine that >50% of NZ diesels would fail that test.

probably more like 95 percent of non computer models.

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