Hey guys I am new here and recently posted a thread in the non-model specific forum, but thought I would try here also. I have a 84 Deville with a 5.7 Diesel, and am interested in possible changing that to a regular gasoline engine. Any advice or thoughts on that would be great. Also some general maintence tips for diesel engines would be great as well. Thank you Dirty
Re: Diesel Engine
The "Olds" diesels were actually far more robust than people give them credit for. There was no real problem with "thin cylinder walls". That's a new one! The issue was that people treated them like gas engines and maintained them the same way. That is to say poorly. Treated properly, the engines would run forever.
Several things happened that caused problems. The most single common mistake was that most people used the wrong oil in those diesels. They put automotive 10W40 oil in them (since that was the most expensive "trick" oil of the early 70's). 10W40 oil was specifically not recommended for the Olds diesels because the high viscosity improver concentration in the 10W40 oils and the relatively poor quality of that viscosity improver package in the oils of that era (those were SE grade oils in that time frame) caused severe ring belt deposits. No diesel engine maker in that time frame recommended any multiviscosity oil much less 10W40 that had more viscosity improvers than any other product. So, people would use the 10W40 oil and it would form deposits in the ring lands and eventually restrict the ring movement and then the engine would loose compression and not start.
Which then brings us to the second big mistake people made with the Olds diesels. They used starting fluid or ether or sometimes WD40 sprayed into the intake to start them. This worked for awhile when the scenario above played out and caused a loss of compression. It would also work in the winter when they were late for work and had forgotten to plug the block heater in and it wouldn't start. Hit it with the ether and hammer down. Trouble was, the pistons in that engine were not the cast iron crowned HD pistons like in big trucks and the Olds diesel had much more compression (22:1) than class 8 diesels. The violent reaction from the ether combustion on the intake stroke would collapse the top ring lands, trap the rings and the rings would stick and lose compression. See above.
Trust me, most all the Olds diesels were "killed" by their owners in the above fashion. My father worked on those engines and I know how sturdy they were. They were not a class 8 truck engine but they were plenty robust enough for passenger car use if maintained and treated correctly. Possibly it was GM's fault for not informing the owners or promising "too much" in the haste to sell them for the fuel economy. Owners really needed to be coached and schooled as to how to treat, operate and maintain them. They are poor engines for short tripping to the post office and food store on a daily basis but they were sold for that use. They probably should have been sold on a limited basis in the Northern states due to poor cold weather startability (as is with most diesels) and/or clear instructions in using the block heater and the importance of it should have been stressed - but, then, if people knew how much trouble they were they wouldn't have bought them.
The other issue in the early ones was the fuel gelling. Most people would buy the wrong fuel during the winter (of course the cheapest fuel was the wrong fuel) and the fuel would gel and plug the fuel filter. So the can of ether came out of the trunk - see above. Later models of the engine came with an electrically heated fuel filter to avoid this problem. Probably should have been there all along but if the right fuel was used, then it wasn't an issue to begin with.
One other "problem" that came up in operation was people's haste to start them. They would not wait for the glow plugs to warm up the engine (and they didn't use the block heater in the winter of course) and they would just start cranking. Then they would remember the glow plugs. The trouble was now there is all this fuel in there. So they would crank and crank. Then they learned how to "jump" the glow plugs to turn them on longer. Trouble there was then the glow plugs would burn out. When the glow plugs burned out and melted they wouldn't come out of the combustion chamber so the mechanic/owner forced them and the tips broke off and stayed in the chamber where they were crushed by the piston the next trip around with 22:1 there isn't much room in there and the resulting damage would take the engine out. Is this the engine's fault? The mechanics and owners claimed it was. I cold never burn out a glow plug using just the key to start the engine but they came in under warranty "burned out" and "melted" all the time. The only explanation was the owners "jumping" them for too long .
The weakest link in the early diesels was the flat tappet cams. Those early engines required frequent oil changes (3000 miles at the most) and the correct oil (oil for HD diesels not automotive oil and especially not 10W40 oil). Once again, people used to gasoline engines used the wrong oils and killed them. Wtih the roller lifter cams in the later engines this problem with the oil was largely avoided but the problem with the 10W40 oil sticking the rings was still there.
Regarding the one that is still running. Someone obviously treated it correctly. Nothing special to do really, just be aware that it is a light duty diesel: NEVER USE STARTING FLUID NO MATTER HOW TEMPTING.
Use the current heavy duty Delvac or Delo or Rotella oils. They are readily available in 15W40 grade at Walmart. Those are excellent oils for that engine. Too bad they weren't around in 1975 or we wouldn't have had so much trouble.
Change the oil every 3000 miles. Contrary to a gas engine and longer change intervals the diesels put so much soot (very abrasive) into the oil that it needs to be changed constantly. Keep it fresh and it will run for a long time.
Change the coolant in the cooling system yearly and use the GM coolant supplement as the diesel could possibly seep coolant into the oil if a small seepage developed. Use the supplement to prevent any stray seepage and change the coolant yearly to fresh, green conventional 50/50 coolant/distilled water.
The mulitviscosity oils of today are so much better than the multiviscosity oils of 1970's that there is no comparison. The SE and SF 10W40 oils that ruined the diesels back then (and a lot of other engines) are history. The current SL oils for diesels are dramatically better. The VI package is fully synthetic and there is ample wear protection in the oil.. Gasoline engines should use an SL oil that is rated GF3 or GF4 (the starburst symbol on the can). You will not that the Delvac, Delo or Rotella oils are NOT GF3-4 rated. That is a good thing for diesels. The GF rating means that the oil is friction modified (among other things) and you do not need nor want that in that early diesel. Use a non-GF3-4 oil such as the Delo , Delvac or Rotella and it'll be fine.
It really is a shame that the Oldsmobile diesels got such a bad rap. They were not nearly as frail as people thought if treated correctly. Slow? Yes! Frugal? Yes! Frail? No! Easy to kill if treated wrong? Yes!
It really soured people on diesels for a long time but it made it easier on the next generation of diesels as people will certainly be better informed and the manufacturers will not take so much for granted in terms of the necessary maintenance and care. Much like the Cadillac "864" but that is a story for another day.
Do a Google search for "Oldsmobile Diesel". There are some excellent websites devoted to the engine as there is still a strong following for them out there. People that can use them correctly and understand their shortcomings get excellent service out of them. Try www.oldsmobileforums.com
P.S. You cannot convert the diesel engine itself to gas operation. Just changing the heads and such wont work. You would need to get a complete driveline from a scrap yard car or buy a crate engine to convert the car to gas.
There is some confusion here as some racers use the diesel block as a foundation for a really stout Oldsmobile race engine but there are many many mods required to do this - the basic diesel engine will not just convert. You have to replace it with another engine within all practical reason for a gas "conversion".
Keep the diesel running and maintained. It will be a real conversation piece in the future and you can use the rant above as a conversation starter.
Wow, thanks for all you help. I do have a question about the block heater however. What exactly is that. The guy I bought the car from said that since the car has two batteries it will start very easily in the winter. Living in Northeast Indiana, the ability to start in the cold is very important. It is not so much of an issue now, but come next november I am sure it will be. Also when I hold down the button for the glow plugs, I start to hear a kind of crackling noise after a few seconds. Does that just mean it is ready to start? Thanks again for your help. Dirty
Wow, thanks for all you help. I do have a question about the block heater however. What exactly is that. The guy I bought the car from said that since the car has two batteries it will start very easily in the winter. Living in Northeast Indiana, the ability to start in the cold is very important. It is not so much of an issue now, but come next november I am sure it will be. Also when I hold down the button for the glow plugs, I start to hear a kind of crackling noise after a few seconds. Does that just mean it is ready to start? Thanks again for your help. Dirty
What's a block heater? There is an electric heating element in the coolant in the block so that can plug the car in at night to keep the engine warm so that it starts easier. Since diesels use the heat of compression for ignition in very cold weather they can be difficult to start. The glow plugs go a long way toward warming up the combustion chambers just before start but the engine is hard to turn over due to the high compression (that is why it has two batteries) so the block heater keeps the engine warm to minimize friction and keep the oil warm for rapid cranking speeds which are positively mandatory for a diesel to start. If your engine doesn't have the block heater I would heartily recommend that you get one installed and use it religiously in the winter.
Button for the glow plugs? In my experience the factory setup had an automatic controller with little yellow and green lights on the dash. You just turn the key on and waited until the yellow light goes out and the green one lights up. What year car is this we're talking about?
Sorry, hit the submit button prematurely. Is the glowplug "button" you mention something that the previous owner installed to bypass the factory automatic controller? Since the glowplugs are buried inside the cylinder head I doubt that you can hear them "sizzling". Maybe it is some wiring or something. The glow plugs draw a lot of current so if someone just hot wired them to a switch the wire size may be way to small or something causing the sizzle noise. I would investigate.
There is a chrome button on the left hand side of the steering wheel, no lights or anything to let me know. He just told me to hold it down for ten seconds and then start the car. After about five or six seconds is when the sizzling noise starts. The car is an 84, and I am not familiar with diesel at all, but I did think that you turned the key and waited for a light to come and when I asked the guy I bought it from about it he looked at me like I was crazy. Good to know that Im not.
Also, I would probably be able to tell if there was a block heater in car already right? Are those easy to install or should I go somewhere and get it done. Is is pricey? Thanks again for your help.
Look under the hood for an electrical cord that would be connected to a block heater. Depending on the type of block heater you get they can be easy to difficult to install. Many of them for those type of engines replace one of the core plugs in the block with the block heater. That takes a little time. You might want to get under the car/engine and look at the sides of the block for a heater unit as the cord may have disappeared.
The glow plug button/control you describe isn't the factory setup. I would investigate as to what the sizzling is. Don't hold the button down for more than 8 seconds. That is the max the glow plugs will reliably take in my experience. Given the years and hacked glow plug control I am surprised that that car is still around. Must be tougher than people give it credit for.
