Diesel engines Diagnosis

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Question: I'm confused about T25 diesels. What ones are there and how to tell a good one?

Peasant: Yes, there are three different ones:

1.6 n/a 50 hp (1982) 1.6 td 69 hp (1985) 1.7 n/a 57 hp (1986 I think, mostly found in governement vehicles, army, post, etc)

Which diesel to buy also depends very much on what you want from it.

The 1.6 n/a is quite tough, durable and very frugal. But it is SLOW, very slow. Particularly so if your asking it to push a fully loaded camper up a hill. Driving up a motorway incline can be a bit of a nightmare, as every truck these days is faster, even fully loaded and they'll be piling up behind you, trying to push you off the road You could live with it if it's for weekends/holidays only ...as a daily driver it's best left in a town/ country lane environement where speed isn't such an issue.

The 1.6 td is well able to keep up with traffic and a pleasure to drive ...up to 60/65 mph that is. Above that it needs considerate driving to keep the temperature in check. Still no motorway cruiser for every day, but ideally suited to make decent progress along A and B roads ...even the occasional overtake is possible.

The 1.7 is sometimes called the "industrial motor". It is marginally quicker and quite a bit stronger than the 1.6 but still no racing machine. It has a very good reputation for reliability. (Which it needs, as a lot of them have been pounded to near destruction by posties and other "professional" drivers)


There aren't that many 1.6 n/a's left. The ones that had a working life are mostly dead ... a low(-ish) mileage one that spent its life pootling around in an early camper could be a good buy, if pootling is what you want to do.

From 85 onwards pretty much all diesels sold into private hands were 1.6td's, as were factory conversions (Westies) so there are a good few of them around. Service history is the thing to look for. Don't be scared by invoices for new head gaskets / new heads or new turbos ...at least you won't have to do it tomorrow.

1.7' s are a bit of a mixed bag. You could find one that spent most of its life in a depot and was well cared for by one dedicated driver, or one that was beaten within an inch of its life every working hour by ever changing jockeys on a minimal maintenance budget (ex parcel delivery vans for example) ...trying to gauge where it came from and how it was most likely driven can be difficult though and mileage alone isn't really an indicator.

The best one for a high top is the 1.6 td ...no question about it. Just make sure you get a healthy one

How to recognise a healthy TD

The best way is to bring along an experienced diesel mechanic or to have the car examined by the AA or any other professional service provider, obviously.

But here are some pointers how to sort the wheat from the chaff on first viewing before forking out money for outside advice:

1) Tell the seller you want to start the engine from cold, so not to drive it that day (if possible)

2) Open engine lid, check engine and fuel pump is dry and not seeping oil or diesel anywhere (a few dark shades are ok, but no moist patches) ..no stains on the driveway

3) pull dipstick, check oil level and look for gunk (moisture/foam) (there souldn't be any)

4) check both coolant vessels for correct levels and signs of oil in water (there souldn't be any)

5) go into the cab, turn the key, check glow plug light comes on, turn off key

6) get seller to start the engine while you stand behind the van. Pre-heating should take about 30 seconds and once the starter kicks in, a good engine starts immediatedly. A puff of smoke is normal and ok ...a big suffocating cloud isn't.

7) once the start-up smoke has cleared the exhaust should be pretty much smokeless, you definetly don't want to see big blue or white clouds and you don't want to smell unburned diesel either

8 ) on idle the thing will clatter and rattle pretty badly, that's normal ...once again check for seeping oil or water, no bubbles in the coolant and then close the engine bay and take it for a drive

9) once up to speed and getting wamer, the clatter and rattle should be replaced by a nice hum without any harsh clonks or pings

10) if you clearly see smoke in the rear view mirror while driving, that's a bad sign. The engine does smoke under acceleration (every diesel does), you can see that in the side mirror if you try to look at the exhaust ...but you shouldn't be able to see it in the rear mirror.

11) it should pull nicely throughout the gears, with a marked push from the turbo at mid range

12) the temp gauge isn't scientifically accurate, anything about 1 cm either side of the LED is normal

13) drive it for a good few miles until it is well warmed up, let it idle and repeat checks 2 - 4 & 8

14) turn off engine, let it sit for a minute ...it should restart without trouble

Once all of this was checked to your satisfaction, it is time to fork out for an expert ...you might just have found a good one

Kermit: In addition to Peasants reply ..

Take a quick look at the condition of the timing belt, its easy enough, just unclip the top of the cover a pull it back, look for any cracks and fraying etc ..

I learnt the hard way when buying my first T25 a few years ago which was a 1.6TD

HarryMann: Nice one peasant! ...to add to that, unless you're buying in darkest coldest winter, cold-starting can only be guesstimated in mid summer, so early morning would be best time to hear it start from cold. Should settle down to a steady idle at about 900 rpm fairly quickly without too much fuss. Many will have turbo in less than A1 condition, so a slight blue haze under power may not be the engine itself.

A good guide is simply, does it respond and pull smooth and well.

Poor cold starting in winter can just be broken glo-plugs (cheap fix), blown glo-plug fusible link (even cheaper) - or if persists , very bad sign for engine condition esp. if combined with smoke when warmed up. A good condition TD should start pretty well in warm weather from cold without waiting for glo-plugs, indicating good compressions.

Service Bulletins, Warnings

1.9TD AAZ Crankshaft pulley bolt- Service Bulletin - Warning


Link to engine diagnosis PDF file (requires adobe reader)

Diesel exhaust smoke diagnosis

general diesel tips and tricks from the US