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About MR688S

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    Over Drive


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    Fixing/Rebuilding Big Rig Trucks and Trailers, Cars, Motorcycles.

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  1. I wish I was on the east coast! I saw a bunch of cool trucks heading out west to the big show in Reno, NV a year or so ago. They looked AMAZING! If anyone knows of anything like this show happening west of the Rocky Mountains, please post it here! Thanks! Have a Great Show!
  2. MC - Thanks for the info. I'll stay with Red Engines on my OTR Tractors. Meanwhile, I'm playing with two Mack MR688S COE tandem axle 80K Tractors with the Renault E-7 E-Tech Engine - 2006, 2007, just before the M-7 came out, well, a "special" US Postal Service Contract run of the COE's. At least they have DAVCO FuelFilter/Water Separators - easy to drain, swap filters, fill and GO! I'm still looking for E-Tech E-7 Manuals to show how to flash the ECU to get the governor turned up or off. All the Best!
  3. Also, MC you mention Mercedes - as in Freightliner Cascadias with the "DD" 15??? It appears that once Mercedes was given Detroit Diesel, they just canned the Series 60 and put up the Mercedes engine and called it a DD whatever. I see lots of plastic and aluminum parts on those engines and they scare me. I saw a video of the top end aluminum cam/rocker holder blocks having their hold down bolts just strip out of the aluminum blocks with helicoils gone bad that are supposed to hold them in place. Why would they put aluminum on such an important part of the engine. When the bolts go, the eng
  4. Thanks MC. I'll see what the local Volvo/Mack people say about that and the price. I run mostly Cummins ISX15's in Internatiional Prostars and I'm happy with them as long as we keep the EGR/DPF Systems clean. These Macks are for a local haul contract that's fairly casual, so, they're not going to be running all the time and we can do maint. on them easily.
  5. Hi, I bought a Mack Postal Service 2006 MR688S and a 2007 MR688P 6x4 and 4x2 COE Tractors and I'm looking for any manuals on them or spec sheets, build sheets, etc... They're running fine, but I like to have the info for maint., etc... I also want to change the E-7 Engine ECU Governor to allow a higher RPM than 1700. Got a response from a Postal Driver that the service raised the trucks he was driving to 2100 RPM. Any later model MR688 people out there with knowledge of the trucks - I'd love to pick your brain for a bit. THANKS! Tomm in Nevada
  6. Hi, looking for an operators manual and a service manual for a 2006 Mack MR688S COE 4x6 Postal Tractor with the E-7 12 Litre Renault Engine and Allison 6 speed Auto Transmission. Real manuals or digital files/CD-ROM's, websites, whatever, as long as I can read them and get info from them. I'm happy to buy the info at reasonable prices. No rush. Here's a pic of what the truck looks like. Thanks!
  7. If there are any MR owners out there who have specs and a service manual, it would be good to chat with you. I've got the truck running smooth and the cab tilting and able to get all the fluids changed and clean her up. The only thing remaining is driveline vibration under torque. If anyone knows of common MR problems in this area it would be good to hear. I'm changing all the U-Joints and the Carrier Bearing for starters and we'll see if things improve. Then, if it needs more attention, I'll get into pinion bearing adjustment and rear transmission yoke issues, etc... Th
  8. Ah, I understand now - the custom MR is just a pic you found, not your truck. I'll stop bugging you about MR specs, etc... All the Best!
  9. GHG - Good to know about the 2100 RPM on a 1996 MR. I found a manual for the Postal MR, so, I'll have more info soon. Thanks!
  10. The only problem I see now is driveline vibration. She gets a vibration under torque in high gear going up hills or stronger acceleration. I let off to keep it from being too drastic. I'm putting in all new U-Joints and a Carrier Bearing and checking yoke positions. If that doesn't fix it, I'll look at pinion bearing adjustment and rear trans yoke for play. I had the rear axle locked out, so, I don't think it's the power divider. Please let me know if you've seen any of these problems. I think it's just the Postal Service letting one of their older units go out to pasture and not wort
  11. Is yours an Automatic? Mine is and it's governed at 60 mph/1700rpm. Have you or anyone you know removed the governor/ECU Flash, etc...? I'd like to get it to at least 63 mph in the 1800 rpm area. I understand the Renault E-7 engine doesn't like to go over 1800 rpm. I don't know until I get a proper manual on this truck. Meanwhile, I'll definitely respect that. Thanks! I started another thread this week on troubleshooting engine issues at the pickup site. After cleaning the DAVCO Fuel Filter/Water Separator, draining the main fuel tank of any water and gunk, and replacing the DAVCO
  12. Oh yeah, I forgot to mention that all the diagrams online for the Mack E-7 engine show and say that the two filters under the left/USA driver's side of the engine are Fuel Filters. They even give a fuel filter part number for them. I reality, they're OIL FILTERS on that tandem manifold. Looks like all the fuel is filtered through the DAVCO Unit and that's it. If anyone knows of other placements of secondary fuel flters on the E-7 Renault engine, please let me know. I haven't been looking real hard after removing the two oil filters and getting them back on the engine and getting the
  13. Miami Cossack - Thanks for the reply. I rebuild wrecks and work on engines all the time. OJT Mack school was cool. I learned that the Postal guys don't do much maint beyond oil, filters, belts, etc... the truck was never cleaned, caked with dirt and grease on the suspension, engine, etc... I'm not for pressure washing engines, but some degreaser and a bit of water from the garden hose goes a long way. I'm steam pressure washing the undercarriage and detailing the engine this weekend. I spent time on the Davco Filter/Separator and found some gunk in the ball check valve that was letting t
  14. 41 Chey - thanks for the reply. I put myself through Mack school that day and that filter water separator was a complete locked up mess the bottom of the unit was black we cleaned it all out with brake cleaner and got it I got a new filter in truck started right up it’s been running great ever since it’s got a little air leak in the in the Davco fuel filter separator it drops down about an inch every man every two hours so we’re gonna work on that and see where the leak is it’s not a not an external leaks but other than that the trucks running great now
  15. Throttle response. I just got this MR688S out of the Postal delivery yard this morning and it limped out missing on one or two cylinders. I took it for a test drive on a back road about a mile and it got progressively worse and now just idles with very little throttle response. Trans was good. Air cleaner clean. Now, looking at clogged fuel filter/s on the drivers side of the engine. The unit also has a DAVCO clear external filter - I don’t know what it does beyond being the first filter, then fuel goes over to the engine filters. Any thoughts? Thanks!
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