turbo life - PeachParts Mercedes-Benz Forum

WANT '71 280SEL · #1 04-16-2003, 12:31 AM

How long does a turbo normally last? I am paranoid that it may go bad. Just curious.
Thanks
David

The Warden · #2 04-16-2003, 12:38 AM

It depends on how well the turbo's been taken care of. If you give the turbo a chance to cool down after a long run and don't exceed 1250°F pre-turbo exhaust temp and change the engine oil regularly, the turbo should last as long as the engine.

However, if you don't keep the oil clean and especially if you don't let the turbo cool down a little bit after a long freeway or hilly run (i.e. where the turbo's working hard), oil left on the shaft going between the two sides can cook onto the metal surface, eventually killing the bearing. It may take a hundred thousand miles for this to manifest itself, but most turbo failures are caused by this. Ideally, you want to get an EGT gauge, but I don't think it's truly necessary on these cars. If you let the engine idle for 45 seconds ot a minute right before shutdown, you should be fine.

Just my $.02...good luck!

Ken300D · #3 04-16-2003, 07:11 AM

I was scared of the turbo part of a turbodiesel too, because of the reputation turbos have on gasolene cars.

However, it turns out that turbos last a lot longer on the MB diesels. As The Warden says, keeping the oil changed is important along with "spinning down".

There are probably more technical reasons the MB turbos last longer. Maybe they are well designed. Maybe diesel exhaust is cooler.

But do not fear the MB turbo.

Ken300D

rwthomas1 · #4 04-16-2003, 10:05 AM

I would be far more concerned about timing chain slack than turbo condition. Turbos are relatively cheap to rebuild and almost never break. They do appreciate a 30sec-1minute cooldown at idle before shutdown after say pulling of the highway, as mentioned above. Synthetic oil is supposed to not "coke" up turbo bearings as bad as dino and it is better at higher temps too. Still many have had great luck with regular dino oil and turbos. I believe diesels do indeed run cooler exhaust temps than gassers but I am not sure. Bottom line is there is nothing to fear with a turbocharger any more than a NA engine. Keep it well maintained and you won't have any problems. RT

gsxr · #5 04-16-2003, 10:15 AM

RT is right: "Bottom line is there is nothing to fear with a turbocharger any more than a NA engine. Keep it well maintained and you won't have any problems." With proper maintenance they often last the life of the engine. Or at least 250-300kmi if not abused. I have seen a few failing recently, particularly wastegate failures (stuck open) on Garrett turbos (OM617 and OM603). And oil leaks are pretty common. But these failures are not terribly common. If you have a bad 617 turbo, you're in luck - you can snag one from a Pick & Pull salvage yard for under 50 bucks.

No such luck with 603's though, they're not common enough in salvage yards yet...

The spin-down thing is really not necessary. HOWEVER you don't want to pull off a mountain grade where you were running with your foot to the floor for several minutes (or other extreme-load condition) and just kill the motor. But in "normal" driving, it is totally unnecessary to do a 30-60sec "cooldown" period. It takes some common sense here - use your judgment and do the cooldown when necessary (which isn't often.)

Turbo engines are brutal on oil due to the extreme heat loads. This is where dino oil really isn't the best. Synthetic can take almost any abuse your turbo can throw at it. Remember those Mobil-1 commercials years ago showing dino & M-1 in a frying pan, and what happened to each at very high temps? Keep that in mind at your next oil change. You can safely extend your drain interval with synthetic to offset the cost, if that's a concern to you. I change my Delvac-1 at 10-15k and have oil analysis results to back that up (the results indicate I could go 20-25k easily).

Regards,

190D22 · #6 04-16-2003, 10:29 AM

I am not afraid of turbos at all, at least on diesels. Most people (pointing at GM people) think diesels and turbos are bad news. My buddy was going to buy a 1988 Mazda RX-7 Turbo II. His old man (who works for GM) told him turbos have lots of problems and to stay away from it. This same guy told me that diesels are bad, they are expensive to get work on and they can have lots of problems. I just laughed in his face. I told my buddy that the RX-7 was a great car, and that his dad is scarred from his GM diesel and turbo past. GM is horrible, that is why their diesels in passenger cars were failures, as were their turbos. I do like some GMs. But I laugh at his ignorant bias.

rwthomas1 · #7 04-16-2003, 02:09 PM

190D22,
I agree that GM is clueless, I agree that GM diesels based on the 5.7 Olds block were at best a bad idea. That said, the GM 6.2-6.5 can be a fine engine if it is used for what it was designed and is maintained. GM failed to properly train technicians and failed to work with Stanadyne in the development of the electronic injection pump in the 94-00 6.5's. The electronic 6.5's can be fine engines but they need to be serviced by a technician that knows what they are doing. GM dealerships don't know how to maintain them, don't know how to troubleshoot them and this leads to poor issue resolution and unhappy customers. I have a GM diesel and like many others it has been essentially trouble-free, reliable and easy to work on. RT

md21722 · #8 04-16-2003, 02:33 PM

They're extremely reliable. My '87 300D has 279Kmi and the turbo works fine and has no external leaks. I've had it since 185Kmi. I never wait 30-60 seconds before shutting down UNLESS I've driven it under load within the past 30 seconds.

The Warden · #9 04-16-2003, 03:08 PM

Diesel exhaust is cooler...I don't remember what the average temps for gas engines are, but diesels don't really get much higher than about 1000° unless it's been modified or there's a problem. Gas engines may be more in the 1500° range, but I'm not 100% sure. In addition, I think that most people with turbo gas engines don't know how to care for their turbo, which would also explain the early failure...

I don't want to continue the turbo cool-down debate (you'll see some people argue that the turbo doesn't need to be cooled down, while others {like me} argue that it does), so my suggestion is that you go with what you're most comfortable with.

Quote:

Originally posted by rwthomas1
I have a GM diesel and like many others it has been essentially trouble-free, reliable and easy to work on.

Just wondering, have you needed to pull the injector pump? Or have you changed out the glow plugs?

I pulled the heads on an '84 6.2l last Christmas (had a bad blowout on the right side head gasket; the owner wound up trashing the engine for a 454 'cause water had sat in the #1 cylinder for over a year, and the cylinder was rusted out), and three big design things that I didn't like (in regards to ease of maintenance) were that the glow plugs and injectors were on the side of the engine, amongst the exhaust manifold. Real pain to get to. Also, because of this, the injector lines went over the valve covers, necessitating removal if you ever need to change the valve cover gasket or take a look at the valvetrainf ro any reason. Lastly, the way the injector pump was mounted, it was necessary to remove the intake manifold to get the pump out. Is this all the same on the 6.5l?

On my Navistar 6.9l, it was a breeze to get the injector pump off when I had to change it out last spring

The glow plugs are also real easy to get to...

gsxr · #10 04-16-2003, 05:20 PM

I don't want to get into a debate either.

I believe this is one of those things that applies to most other turbo engines, so people think it automatically applies to Mercedes diesels. But, IMO, in this case it doesn't entirely. Mercedes over-engineered this just like anything else. I believe MB turbodiesels don't require a cooldown period before every shutdown. There just aren't a rash of MB turbo failures to back up claims otherwise. I'm not saying it's a bad thing, it sure won't hurt anything to let it idle a bit before shutdown... just that you don't need to do it all the time!

Now if you live at the top of a steep hill or something, please take that into consideration... my normal commute involves parking lots and 25mph zones at each end which act as plenty of "cooldown" period for me.

psfred · #11 04-16-2003, 09:11 PM

Turbo cooldown is recommended in all owners manuals for turbos, gas or diesel. Gas engines are worse, by far, and almost no one (my brother in law included) does it. They all also have to have the turbo rebuilt once in a while from coking oil on the shaft.

Under high load (90 mph on the interstate), the tubine wheel will be bright red or hotter. It's cooled by the oil (or water, since most gas turbos have a coolant passage too) while the engine is running, but only by conduction to the rest of the turbo when the engine is not. Red hot is enough to coke even synthetic if it stays that hot any length of time.

Therefore, any time you don't idle down naturally (that quarter mile into the parking lot or driveway), cool it down a while by letting the engine idle. The worst thing in the world for a turbo is the interstate rest stop, where you can go from 80 to zero in 20 seconds and park. It's not a bad idea to let the engine dump excess heat anyway under those conditions.

Peter

#12 05-04-2003, 03:37 PM

It will last pretty long.

rwthomas1 · #13 05-04-2003, 09:49 PM

Just noticed the post on GM's. Yes the 6.5 is like the 6.2, you have to take the intake off to get to the IP. No big deal, its easy to get off. Glowplugs are easy on the drivers side. Passenger side is a be-tch! 2 are doable and two are impossible. However the GM's don't have cavitation problems the Navistar 6.9-7.3's do so its a wash I think. RT

The Warden · #14 05-04-2003, 11:11 PM

Quote:

Originally posted by rwthomas1
Passenger side is a be-tch! 2 are doable and two are impossible. However the GM's don't have cavitation problems the Navistar 6.9-7.3's do so its a wash I think. RT

I think that I wound up using a small wrench on the two rearmost plugs, and 1/4" drive sockets on the others...also lost the wrench at one point

and had to dig on the grass that the truck was parked in to find it. Fun times, eh?

Also, BTW, you're right that cavitation's a serious problem with the IDI 7.3l's, but it's rare on 6.9l's (thicker cylinder walls to begin with). In addition, there's an additive that you can put in the coolant that acts as a sacrificial goat, and is very effective at preventing the cavitation. Unless the additive was used religiously, I wouldn't consider a used 7.3l IDI, for that exact reason...

Just thought you'd be interested

rwthomas1 · #15 05-05-2003, 12:17 AM

Yeah Warden you are correct. Small wrenchs and 1/4drive extensions, etc. to get to the glowplugs. I actually removed the turbo on my truck to do injectors and did the plugs while I was in there as PM. I wouldn't consider a 7.3 either unless it came with dealer service records for its entire life. I remember reading somewhere that there was a disconnect with Ford and Navistar on the issue and Ford didn't even have the anti-cavitation additive as PM in the owners manual for a couple of years. Don't know that for sure but I do know they did quite a few warranty blocks on them. All the diesels have their pros and cons. You just have to choose what issues you can live with. Didn't the 6.9s have head-cracking problems for a few years? The GMs crack heads too but believe it or not the cracks aren't serious. They occur between the intake and exhaust valve seats. There is a sleeve repair kit for where the crack penetrates a drilled water passage. Once that is done the cracked heads are good to go and will never give any more trouble. Its like Ripleys Believe it or Not! RT