Improving Mercedes OM603 engine efficiency
Hi All,
Back after a long time away, I now have a Mercedes s124 with the 3.0 6cyl 12v OM603 engine. It's normally aspirated, so no turbo to benefit from. The car is heavy at 3500lbs, and has 113bhp coupled to a 4speed auto. I am also running it on Veg oil (SVO/filtered WVO) At up to 90% oil. The car has been run on this for years by previous owners, and seems happy enough. The engine definitely is not in its first flush of youth (316k miles), and I've ordered Oil/oil filter Air filter Main fuel filter Pre fuel filter Thermostat To give it a service. My initial plan is to carry out the service, and check the fluid levels in the autobox and diff, but I was wondering if there were any other elements that should be checked on the engine (pump/fuel system/inlet/valvetrain etc)? Additionally, I think some more power would assist re economy - it feels as if you are ALWAYS accelerating! Does anyone know what can be done to boost performance/restore to at least original? |
A rebuild wouldn't be a bad idea. I'm not all that familiar with diesels but after those miles I doubt the rings are as tight as they were when new. This is, of course, quite a bit of money to put into the car. A turbo would probably help with both power and economy, but again money.
On the cheap? Probably wait for someone else to chime in who owns a small diesel. |
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Nice merc! Now that is what i call a roomy stw.
I would get the injectors and fuel pump/fuel pumps timing checked and maybe adjusted. It might bring some power back even. You mentioned on the "introductions" thread you are getting 23mpg, sounds way too much even for an automatic. Also, check for possible brake drag. I once had a 124 myself, sedan with 2litre diesel+4speed manual. Sluggish but reliable, one of the best cars i had :thumbup: |
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Brake drag had also crossed my mind. No obviously warm wheels when I check. I got started on the servicing today, hopefully that will bring some more MPGs..especially now it gets up to operating temp! According to the EPA site, the w126 saloon (300SDL) with this engine (normally aspirated) is the closest I can find to my car (all the w124 models are saloons or turbo diesels) and it gets 21 urban, 24 highway 22 combined Quote:
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had some of a chance to tinker with this today..
First up, the thermostat. It's held on by 2 10mm bolts: Top one seen here https://ecomodder.com/forum/member-3...105-114309.jpg Bottom one accessed via 3/8 ratchet and extension https://ecomodder.com/forum/member-3...105-114638.jpg It was patently obvious what was up with the old stat: https://ecomodder.com/forum/member-3...105-115009.jpg The new one was fitted (took 2 attempts to get it to seat properly) and new coolant was added and bled through. I found removing the hose next to where the thermostat mounts means you can put the stat in its holder, and slot into the block. This means the stat stays in place and seals properly Result? https://ecomodder.com/forum/member-3...05-wa0002.jpeg A nice solid 90, and working heaters:) The fuel level sender is also on the list of things to do.. A test drive revealed no problems so I returned to look at replacing the stop solenoid. Initial inspection said it looked like too large a job to do in the time and light available, so it waits for another day. Next it was "what do these switches do?" https://ecomodder.com/forum/member-3...105-131258.jpg https://ecomodder.com/forum/member-3...105-131251.jpg The answer is nothing obvious, bar the green one lighting up.. anyone any ideas? Then it was "hunt the exhaust blows" That'll be the centre one... https://ecomodder.com/forum/member-3...105-152810.jpg And This will be the rear one.. https://ecomodder.com/forum/member-3...105-152845.jpg Gauges at the end of the 40 miles run home. https://ecomodder.com/forum/member-3...105-174940.jpg Sat nice and solid there regardless of speed. You can see the oil gauge is showing that the oil is sufficiently warm to have thinned properly, which means the engine is at full operating temp. I swear it feels nicer to drive - almost as if the engine is working more effectively (and the veg is warmer!) Hopefully this will bear out in an economy increase.. almost 1/2 a tank down so should find out soon. |
Temperature control is extremely critical on a Diesel, most noticeably an IDI running on veg oils :D
BTW did it ever had a glowplug bypass? An uncle of mine did it in a Suzuki Vitara repowered with a Volkswagen 1.6D engine he used to own, having to press a button to control the glowplugs at every cold start instead of switching it to operate automatically. |
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Tonight, at an undisclosed location near Baurheid, the Merc met it's Nemesis..
THE PIT! https://ecomodder.com/forum/attachme...1&d=1547677044 The Merc fears the pit as it exposes all its weaknesses. The principal task was to stop the exhaust blowing as much. Under I went https://ecomodder.com/forum/attachme...1&d=1547677232 The news was not good.. https://ecomodder.com/forum/attachme...1&d=1547677537 https://ecomodder.com/forum/attachme...1&d=1547677744 https://ecomodder.com/forum/attachme...1&d=1547678006 https://ecomodder.com/forum/attachme...1&d=1547677876 However, I had a plan. And it was a good plan. Gungum and Exhaust bandage to the rescue! https://ecomodder.com/forum/attachme...1&d=1547678438 https://ecomodder.com/forum/attachme...1&d=1547678525 The result? It's not ****ting out veg fumes from all over the shop. This pic was taken with it running https://ecomodder.com/forum/attachme...1&d=1547678715 Hopefully that should help fuel consumption a bit too |
Here's a quick look at the SVO/WVO the car is running on, along with a cold start in -3 degrees
https://youtu.be/nJaa1KDJReY |
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And so to the oil service.
After a run out to get scran in for lunch, the Merc was up to temp, and oil extraction could begin. Don't tell Junkman, but this om603 takes 8!!!! Litres of 10w40 for an oil and filter change. Whilst the PELA did it's thing (and keeping an eye on it, as it only holds 6L at a time!) I set to removing the oil filter. First, it was bonnet to 'service' position, and then loosening the single 13mm bolt, and 2 13mm nuts holding the filter housing lid on. https://ecomodder.com/forum/attachme...1&d=1547940495 The construction is similar to the filter housings on the BMW M30 engine, but much more over engineered. The BMW only has a central 13mm bolt. It keeps pressure even round the top seal, so God knows why there are an additional 2 13mm nuts holding the filter lid on the Merc? The 2 13mm nuts come off straight away, but the 13mm bolt needs unscrewing and removing to allow the lid off past the bulkhead. https://ecomodder.com/forum/attachme...1&d=1547940594 The old filter was tired, and the stylish* Waffle construction of the lid can be seen. https://ecomodder.com/forum/attachme...1&d=1547940660 Next step was cleaning out the filter housing And getting the new filter popped in . Marvel at the handle ! https://ecomodder.com/forum/attachme...1&d=1547940732 Once everything was buttoned back up, fresh 10w40 was poured in(Asda had it at £13 per 5L). The old oil was popped into containers for later processing*. The result? Much quieter running - on the motorway at about 75-80mph at a light throttle, it sounds for all the world like a large capacity 6 cylinder petrol.. I'm growing to like this tub! |
431.4 miles covered, 62.39L used (56L veg, 6.39 L Derv)
Giving 31.43mpg (imp) 26.17mpg (US) |
Since the last fuelling (the first with some WVO in it) she has been grumpy to start.. OM603 non turbo
My thinking is filters (unknown how long they have been on) or the fuel mix isn't working - anyone any suggestions? Video at link below https://youtu.be/eDzjZb5pMxE |
Can it be thickening? Maybe some diesel 911 or related.
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drove it a mile up the road, did what I was doing (90mins passed) and it started fine first heat when I came to go back down the road. |
Ive got a om606 merc I run on veg. In this temp I add 5-10% petrol to thin it out, as well as add 2ehn to raise the cetane back up.
om606 has a factory fuel/coolant heat exchanger build into the heads so I didnt have to worry. If yours doesnt I'd get one. I also have a 12v sillicone heating pad wrapped around my fuel filter to help warm it up before the engine has got to temp. |
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I may try something petrol in it if the filters have no impact. Cheers |
The last tank was 430.1miles to 67L - giving 24.3mpg US
This tank included a lot of town driving and a fair amount of cold starts (down to -6 Celsius). It's not the worst, but definitely could be improved upon. Being a heavy car with a tired autobox and low power, it feels like you are always accelerating - something I need to try and avoid. With it being mechanical pump, I don't even get DFCO :( Initial thoughts are: Remove the extraneous junk/tools from the boot Add a little more air to the tyres. Work out the shift patterns of the gear box more effectively. Longer term: Autobox fluid and filter change Diff oil service Replace exhaust Advance fuel pump timing (it alters as the chain wears, MB suggest 1-2 degrees for every 100k miles) |
Last night, I had this out on an epic adventure - covering about 120miles in deepest, darkest central belt.
Observations: It's nearly as quick with your foot just resting, but not engaging kickdown as it is where you are 'Double kickdown BANZAI" A B road blaster it is not, although it grips bloody well, and once speed is achieved, it can be maintained! The headlight aim could do with some work. Front lower arms are needed - is it a garage job? The gearbox is a bit doddery - a fluid and filter change would be beneficial. Lastly, and most importantly, I do enjoy driving it - it's so comfortable, and once you work out how the engine likes to be used, it'll happily keep up with traffic. I got out at the end and felt like I'd just driven to the local supermarket. |
I have found this YouTube channel “MercedesSource” has a lot of useful information about older Mercedes Diesel vehicles. Would send you a link but not allowed.
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Thanks, already watched a fair few of his videos - helpful if a bit long winded.. |
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Tonight I entered to collect a bulk load of fuel.
Jim had made an excellent start by setting up the pump, then forgetting it would siphon.. Oh how we laughed:) https://ecomodder.com/forum/attachme...1&d=1550271035 Next up was to start pulling the containers out the back of the car and get filling. https://ecomodder.com/forum/attachme...1&d=1550271861 The pump was heavily aerating the veg ( you can see it on the 20L tubs on the LHS of the above picture), so we watched it settle as we continued to fill. It rapidly cleared to a lovely looking liquid, so we just boshed 20L in the tank:) In fairly short order 230L was pumped. 210 in containers and 20L in the tank. We'll likely filter the 210L unless the Merc ain't grumbly on what's in it:) https://ecomodder.com/forum/attachme...1&d=1550272010 https://ecomodder.com/forum/attachme...1&d=1550272123 |
Being a heavy car with a tired autobox and low power, it feels like you are always accelerating - something I need to try and avoid.
With it being mechanical pump, I don't even get DFCO :( .................................................. ................................... I have a surprise for you. Machanical pumps has DFCO feature build in. If you decelerate or go downhill the pump turns faster than what your foot demands. So no diesel is pumped to injectors. Test procedure: Drive downhill on straight slope in gear, take foot off diesel pedal, listen to engine, switch off engine (Don't remove key!! or engage steering lock!!), listen to engine, switch on engine. You will hear no difference, which means it has DFCO. Enjoy:) |
Couple things you can do, that I did with my 1.6 Jetta diesel: 1. wrap a nicrome wire around each injector, attach to your battery via a relay keyed to your ignition. Ignition on, the wires almost instantly warm up to 200 F(depending on wire type, length, thickness) which then warms your incoming fuel.
2. modify your rev limiter, so that it doesn't start cutting off your fuel @3000rpm, and lets you get full fueling all the way to your rev limit before cutting off the fuel. Both create a big improvement in driveability, and preheating the oil will save you a LOT of engine damage (coking of injectors& combustion chamber, lubricating oil turning int sludge, etc) |
Well, nowadays some spark-ignited flexfuel cars rely on a similar system to pre-heat ethanol as a cold starting aid, but I don't know about any Diesel featuring it as a factory-fit.
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I hope you've changed any o rings on the fuel pipes, if your engine has them that is. I'm not familiar with om603.
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You want cheap? But an old corolla. |
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Went out to this in the morning, and she just wound over and over and over. Battery got drained and not even a cough.
Luckily, my neighbour was performing a thorough* check of his Disco 2 before heading to Skye for the weekend. He discovered a need for 2L of oil, but only had one. I swapped him a litre for a jumpstart. Leads connected and away it went no bother. This suggested to me that it was struggling to pull fuel through with just the battery in the car. The filters on the car had been on it since I got it, so no doubt overdue a swap. Anyways, with it running, it was time to head to the unit. Once there, I had a look at the pre-filter https://ecomodder.com/forum/attachme...1&d=1552173464 Definitely got my monies worth out of it! A new one was swapped on https://ecomodder.com/forum/attachme...1&d=1552173555 Then it was time to check the main filter: https://ecomodder.com/forum/attachme...1&d=1552173652 Who knows how this ever ran.. Anyways, a new Main filter was sorted, and the car fired up and taken for a test drive. All well, and possibly a slightly perceptible increase in performance.. Ever since the car has been mine it has been howling inside - I think previous owners have done over 200K on veg, and I reckon they could have done another 20K on the veg that was in the interior.. The plan was simple - a £10 valet https://ecomodder.com/forum/attachme...1&d=1552173793 The attack was thus: Hoover Upholstery cleaners plus scrubby brush for seats and doorcards Hoover again Wipes for all the plastic/trim Windows cleaned. I used no less than 9 half buckets of water (changing it when dirty) and about 40 wipes. An example - the back of the boot prior https://ecomodder.com/forum/attachme...1&d=1552173875 And after https://ecomodder.com/forum/attachme...1&d=1552173988 In total this took about 5 hours. It felt like I removed about 100kg of utter crud from it. Whilst the fan heater whirred in the interior, I turned my craftsmanship to the exterior: One crusty arch: https://ecomodder.com/forum/attachme...1&d=1552174049 Exceptional surface preparation (handheld wire brush held somewhere near the panel) https://ecomodder.com/forum/attachme...1&d=1552174260 Seamless https://ecomodder.com/forum/attachme...1&d=1552174345 It'll do until I can be arsed. I left it up at the unit with doors open to finish drying out, and brought the A2 loaner home.. Thoughts on that to be put elsewhere:) |
My god that trunk was in a hideous shape:D
Nice job on the cleaning, though:thumbup: |
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I also have febreze to spray on the upholstery - should help again. In other news, the filter swap seems to have made it more responsive at partial throttle, which is encouraging. I also treated it to a new 14" rear wiper - allowing me to wipe the smoke particles that settle on the screen more effectively. It'll be off on a big old roadtrip this week - circa 800miles. Will be interesting to see how the MPG works out:) |
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The first tank of the roadtrip has been finished, and the next one should be done shortly.
The first tank saw 467.6 miles completed for 65L of zero cost WVO. A new best mpg of 27.23 (32.7imp) However, it was no without incident! As Hot Chocolate would say "It started with an FTP" (Failure To Proceed = failure to start) I had to jump through Merc with the Clio. I suspect the battery is on its last legs. Down to Tebay ( a motorway service station), no bother. Then it threw a low coolant light as we pulled in to park. We scranned then found something for free at Tebay : Water https://ecomodder.com/forum/attachme...1&d=1552776593 You can see the 3 part cap that shouldn't be 3 parts here https://ecomodder.com/forum/attachme...1&d=1552776899 A new one has been ordered from Mercedes Benz (£8.50/$11.50) and will be fitted asap. Switching on the heater caused the light to come back on, so e added a litre of coolant, and it remained off. We think it didn't bleed properly when the thermostat was replaced. We arrived in to Wales, and set to work on the other car.. https://ecomodder.com/forum/attachme...1&d=1552777260 Much as done on the Golf, but we ran short on time and had to do a late night dash back home (arriving back at 3.05am on Saturday morning) Here's the car getting the last of the WVO we had carried before the final stint up the road. https://ecomodder.com/forum/attachme...1&d=1552777570 It does do sustained highish speed cruising with aplomb, and is a most comfortable mile muncher despite nearly 320K on the clock. |
I haven't seen a convertible Golf for a while.
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increasing efficiency
Diesels like heat- they tend to run best when you put in the highest temp thermostat you can find. Raising the temp on any IC engine raises the thermal efficiency- Gas or diesel. I got my best MPG on my 1986 Jetta diesel by using this coolant https://www.evanscoolant.com/ and partially blocking the radiator.
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Having replaced the stat, I'm happy with how it heats up now, and the roadtrip served to bleed the system through well. At the moment I'll leave her be - I think the more pressing work will be getting the autobox fluid changed as I think it's a bigger issue at the moment |
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