Hello Everyone,

I am looking at a clean, well-maintained 740 Turbodiesel. It is pricey, but I have always liked the 740 series and having the TD, which is rare, makes it even more appealing.

What is that I should know when considering a 35 year old 740?

 

Welcome to the forum. For body and non-engine mechanicals, just read through posts on the 240/740/940 forum. Much of the discussion will be on gas engine stuff - you may want to check out the UK forum for oil burner specific questions. As with any 35 year old car, they will need upkeep and odd repairs from time to time so if you're up for the DIY work, most people on this forum agree they are a great car to work on and can last and last. Just do a full inspection to know what your getting (checking for rust/dents/corrosion, check all rubber bits in the suspension and other parts that age, test for fuel pressure/engine compression etc) and so on.

 

I've never heard anything good about a Volvo diesel. Its a Volkswagen D24 motor, which was a 6 cyl extended version of the 4 cyl VW diesel used in early Golfs(Rabbits) and such. They don't like frequent short trips, they don't like being driven cold, and they are prone to head gasket failure, head cracks, and such. Most of them had adjustable valve tappets, and should be checked and adjusted every 25000 miles. timing belt interval is the same 60K as the gassers, but its harder to do because the longer block leaves less room.

if its from 1982 to mid 1987, the whole car is prone to electrical problems due to 'biodegradable' wiring insulation.

 

Thanks for the replies so far. My father had a 1980 244 diesel and it was a beast - but had blow by at 70K miles. I think a lot of the issues were resolved by 1986, which is the year of the 740 I am looking at. How can one tell if the wiring insulation is degrading? Is there a spot some place on the car where is evident and visible?

I have been reading the forums. I have learned a lot already on the car in general. Nothing really stands out as a major problem area. I have learned that the 1986+ models have some advantages over earlier models. I will keep reading.

 

the first part of the harness to go is usually the individual wire insulation inside the black outer sheaths, where its getting the hottest due to proximity with the engine.

now, a diesel has less wiring than a gasser, there's no ignition system. I don't know what sort of injection the D24T uses.... ok, wikipedia says its mechanical, so thats even less engine specific wiring.

this is an extreme case...

 

Thanks, if I end up going to look at it, there is growing list of things to inspect. Could be there hours. I did some reading on Swedishbricks, and I learned about the inconsistent distribution of cold engine oil during short trips. The one I am looking at has 123k on it and was dealer serviced with records. I will have to ask for those records and see how often the service intervals were to get an idea of how many miles it was driven in between - and see if I can determine if these were short daily trips or long stretches of being parked.

Looks like finding a local diesel specialist to do a compression test and possibly a cylinder leak-down test may be wise too.

 

diesels in general are best used for long distance trips. I cringe every time I have to use my F250 diesel to make a local run (garden store, dump), but thats offset by the majority of its uses which are hauling my camper 100s of miles ... Folks that just drive a couple miles at a time should NOT have diesels. Really short trips all the time are bad for gas engines, too. Was trying to help a guy on a mercedes forum with an older 300E who was having all kinds of problems, yet his car was quite low miles for a 1990-ish car... Then I found out his normal week was 3-4 round trips of less than 1/2 mile to work, and he NEVER went more than 2-3 miles a day. omg, get a bicycle or something. his oil was never getting hot, so it never boiled off the condensation, so the whole top end of his engine was rusty.

 

Wow. With Corona, my Subaru's 75 mile round trip + 1-5 mile trips to local parks to walk the dog 2x/day has turned into just the 1-5 mile trips per day. About every third day, I make sure I drive it at least 10 miles one way with a roundabout way home to burn up condensation in the oil and exhaust. Today, I took it for an extended ride again. Better for the brakes too.

So, I will send an email asking for the service records first. Then I will take it from there and see what to do. I don't want to buy a headache.

 

These old euro diesels, any make that vintage, are super gross poluters, like hundreds of times more than a modern car, hipsters love them but that means nothing. They are in fact banned in many EU contries unless modified with soot filters, etc. That, besides really bad performance, much more pricey parts impossible to get anymore, and few shops know anything about them but yes, they get better mileage... I had 740 diesel back when and it was with many problems. You can own one for the rarity factor, but as a car for use, a b230NA is far better.

 

This car would not be my daily driver. I would have it as a collector car, as it is rare. It would spend a majority of time in the garage, probably take it out for pleasure drives. I can't imagine it getting more than 5,000 miles in a year.

 

The allegedly better fuel consumption of Diesel engines in passenger cars is largely either a misunderstanding or a myth.
Measure it in miles per gallon (US) or liters per hectokilometer, (the rest of the world) and it looks pretty good.
But only because there's more fuel in a gallon of Diesel fuel than in a gallon of gasoline. Measure it in miles per kilogram, or miles per ton of petroleum required, and the advantage disappears.

Diesel engines of that era are notorious emitters of NOx, which isn't visible but is responsible for a lot of acid rain. (and nitric & nitrous acids in the exhaust system)

 

For practical reasons, "more fuel in diesel than in gas..." means nothing although I am sure you have some way of explaining that. I am not a diesel fan overall but having tried many over the years, both in the US and in Europe, I can tell you that the VW group of TDIs reach spectacular fuel efficiency often achieving way better economy than officially recognized numbers. A VW Jetta TDI can often surpass 60 MPG in highway driving while a gas powered one cannot come close.

 

what he meant is, a gallon of diesel has more energy in it than a gallon of gas

 

A gallon of Diesel fuel also contains more fuel. More mass. More hydrogen atoms and more carbon atoms.

 

Being the practical type, I don't see what different that makes--a gallon of fuel goes so far, the price of the fuel is what matters, that and the MPG, so much for the economy side of the issue... What's in the gallon, that's beyond my concerns...

 

No matter how you slice it -- miles per dollar, miles per kg of petroleum, miles per kg of NOx emitted, miles per liter of contaminated lubricating oil -- there's just no compelling reason for a Diesel engine in a passenger car.

Especially now, with the price of Diesel fuel being double that of gasoline.
Even in "normal" times -- which we probably won't see again for at least a year or two -- the price difference far exceeds the energy difference.

Miles per gallon is a distraction, an anomaly that overlooks an important difference.
And reports of a VW getting 60 mi/gal need to examined closely. Chances are, they're either cheating on the emissions or using Imperial gallons.

About the only useful difference would be miles per fill-up, if you lived somewhere like the Australian Outback where filling stations were few and far between. But even then, you're only going to see about a 12% advantage.

Don't get me wrong; I like Diesel engines. My all-time favorite engine (the GM 567) is a Diesel engine.
(yes, I'm the kind of uber-geek who has an all-time favorite engine)
But there's an appropriate time, place & manner for everything.

 

Those reports, that's my personal experience driving around Europe in a Skoda Octavia 1.9 TDI getting as much as 75 MPG on long stretches at moderate speeds, reliably 60+ MPG. A Skoda Octavia is Passat size VW Group car made in Czech Republic...

The fuel savings of diesel vs gas engines are in the range of 30%, conservatively speaking and that applies to the range of vehicles from SUVs to small passenger cars, I can't speak of semis and such but since they are all diesels, the whole industry can't be wrong!

 

for sure, my 7.3L Ford Powerstroke F250 gets way better gas mileage towing a trailer on long interstate runs than my Toyota 4.0L gas V6 ever did

 

if i recall correctly my '79 vw rabbit diesel 5spd used to easily get 50mpg on the highway - 60 no way... it was a good car for long trips until the block cracked...
i believe those semis you see all over only get around 10mpg...??

 

If you achieved 10 miles/US gallon in an 80,000-pound semi, you'd either have everybody wanting to learn your secret. or be dismissed entirely for making preposterous claims. Seven is much more typical.

What do a 1979 VW Diesel and a Czechoslovakian Skoda Octavia have in common?
Lack of contemporary emission controls.

Why should you be skeptical of claims of exceptional fuel economy in Europe?
In addition to the usual selective observations -- "I once achieved 75 mi/gal going downhill with a tailwind, little traffic and drafting a bus at a steady 50 mi/hr with a fully warmed-up engine" (although my average for the year was half that) -- they're often using Imperial gallons. Canadian cars achieve 20% better miles-per-gallon than their American counterparts for the same reason.

Why are passenger-car Diesel engines so much more expensive than gas?
Manufacturers need a cash reserve for paying fines for cheating on emission standards.
from today's news: https://www.wardsauto.com/engines/vo...elgate-fallout

What do an 80,000-pound semi and a Ford Powerstroke with a heavy trailer have in common?
They're not passenger cars.

- - -

If the price of a gallon of Diesel fuel is 20% more than a gallon of gasoline -- which is the usual case in the United States -- there's just no compelling reason for a Diesel engine in a passenger car.

If it's a daily driver whose drive cycle includes a lot of short trips and an engine that's less than fully warmed up, a Diesel engine is usually a bad idea.

But if you want to drive a rare, pricey museum piece, and you don't mind either the more-intensive maintenance schedule, the lack of parts availability or poisoning your neighborhood with NOx, then go for it.