MDS question

[RVGuy]

Hey all,

I've had MDS turned off (manually by selecting gears) essentially since I bought my truck with 8 miles on the odometer. I had read somewhere that the MDS could cause damage to the truck, specifically the dreaded lifter failure.
That was almost 5 years ago and I've done quite a bit of reading (and driving, I'm at 158,500 miles now) since then and I'm not sure it's true. Is there any actual evidence that the MDS could be the cause of any long term damage to the engine? I mean the system has been out for, what, 14 years or so now? I'd think if it was some horrible thing there'd be huge uproar and widespread failures but I still see a lot of 3rd gens and pre-2013 1500s with the 5.7 rolling around here. Not to mention all the other vehicles with the MDS in them on the road.
I'm not trying to debate if the MDS really does anything for fuel economy. I've let mine run for a few tanks of gas here and there and for my driving style and commute is does actually make a worthwhile difference when I hand calculate my mileage. I'd like to just let the MDS run but I'm concerned about it doing harm to the truck. I want to milk as many miles out of this thing as possible before I buy another truck so to me longevity trumps fuel economy.

So, what's the verdict? Is MDS actually harmful to the hemi or is that an old wives tale made up because we just love to hear that V8 growl all the time?

 

[Brandon-w]

My mds lifter collapsed and started hammering on my cam lobe. Being a mechanic I caught it quickly and knew what it was. I replaced lifters with non mds and a new lumpy cam. There are a few guys who have had the same issue as me. Id hate to admit it but I think it's more common than you think.

 

[Octane]

My mds lifter collapsed and started hammering on my cam lobe. Being a mechanic I caught it quickly and knew what it was. I replaced lifters with non mds and a new lumpy cam. There are a few guys who have had the same issue as me. Id hate to admit it but I think it's more common than you think.

I'll always believe it's cheap bearings in the lifters.Companies taking bids on whoever will supply parts for the cheapest price is not always conducive to getting a quality part/product.

 

[Brandon-w]

I agree with you there! Lowest bidder gets it...

 

[Octane]

I agree with you there! Lowest bidder gets it...

And the bid winner will absolutely promise that carmaker that they will still have a quality product even though they win the low bid,because they want that business contract bad!Lot of money at stake.

 

[RVGuy]

My mds lifter collapsed and started hammering on my cam lobe. Being a mechanic I caught it quickly and knew what it was. I replaced lifters with non mds and a new lumpy cam. There are a few guys who have had the same issue as me. Id hate to admit it but I think it's more common than you think.

I'm not wondering whether or not it happens, but if it's the MDS that causes it. If running with the MDS off will increase my chances of the engine lasting longer I'll continue to shut it off. Alternatively though, if the MDS isn't hurting anything I'd like to run it so I can save some money, then if I do need to do this repair at some point I'm a little bit ahead financially as opposed to spending more on gas than I needed to.

 

[Brandon-w]

And the bid winner will absolutely promise that carmaker that they will still have a quality product even though they win the low bid,because they want that business contract bad!Lot of money at stake.

Well atleast we'd hope... But the eco diesels don't seem like they have any luck with the egr coolers either. [emoji1787] I often wonder the quality of parts they've been using these days. Seems like these days they just want it out the door. Sisters 2019 sport body panels aren't even lined up properly straight from factory.... Seems they need a new quality control officer.

 

[Brandon-w]

I'm not wondering whether or not it happens, but if it's the MDS that causes it. If running with the MDS off will increase my chances of the engine lasting longer I'll continue to shut it off. Alternatively though, if the MDS isn't hurting anything I'd like to run it so I can save some money, then if I do need to do this repair at some point I'm a little bit ahead financially as opposed to spending more on gas than I needed to.

I would always run with it off. If you want to prevent something from wearing out and causing issues don't use it. Not saying it won't go bad anyways but it's more prevention than running it. Just my 2 cents tho. I had mine off with the tuner and the lifter still failed so its basically roulette. I'm also a spaz about maintenance so it's not from lack of in my case.

 

[RVGuy]

I would always run with it off. If you want to prevent something from wearing out and causing issues don't use it. Not saying it won't go bad anyways but it's more prevention than running it. Just my 2 cents tho. I had mine off with the tuner and the lifter still failed so its basically roulette. I'm also a spaz about maintenance so it's not from lack of in my case.

I appreciate the response, that's exactly the type of information I'm looking for. Especially since you're more experienced with these engines than I am (I haven't really worked on anything newer than the 50s and that was a single cylinder carbed engine).
Sounds like I'll just keep switching it off then.

 

[gofishn]

14 and up, run with no MDS. If and when you rebuild the engine, remove it entirely and go with better lifters.
Been reading this stuff for last 5 years, had lifter failure and cam replaced under warranty, always ran PUP regular oil change ntervals and still had the issue, truck hardly ever idles and I drive 189 miles to work so short drives are not an issue.

DIsengaging MDS IS the only thing I did not practice.,
I Do now.

 

[Octane]

I appreciate the response, that's exactly the type of information I'm looking for. Especially since you're more experienced with these engines than I am (I haven't really worked on anything newer than the 50s and that was a single cylinder carbed engine).
Sounds like I'll just keep switching it off then.

I always disable my mds with gearshift but my engine is already over 100k so if any failure happens I'll just put a new engine in anyway.I dont see much point in replacing lifters cam timing gear set gaskets etc on a high mileage engine when it would be easier for me to swap motors and less greasy too!

 

[gofishn]

I always disable my mds with gearshift but my engine is already over 100k so if any failure happens I'll just put a new engine in anyway.I dont see much point in replacing lifters cam timing gear set gaskets etc on a high mileage engine when it would be easier for me to swap motors and less greasy too!

Still others do not see any point in putting any engine into a older truck and go easiest route: buy another truck.

 

[Brandon-w]

Still others do not see any point in putting any engine into a older truck and go easiest route: buy another truck.

I think it depends on the situation. On my current hemi which I still owe money on yeah Id definately trade if it gave me any more issues. On the other hand an older truck, that's paid off, dont owe me a thing and if the body is good I'd drop an engine in it knowing the money was well spent. It just makes sense, I'm not locked into $500+ a month payments for the next 5-8 yrs and I can throw cheap insurance on it and save money there aswell.

 

[gofishn]

I think it depends on the situation. On my current hemi which I still owe money on yeah Id definately trade if it gave me any more issues. On the other hand an older truck, that's paid off, dont owe me a thing and if the body is good I'd drop an engine in it knowing the money was well spent. It just makes sense, I'm not locked into $500+ a month payments for the next 5-8 yrs and I can throw cheap insurance on it and save money there aswell.

Agreed.

I meant was each his own. I would take out my own motor, send it away to shops whose work I have known for decades, get everything done, then re-assembly it, myself with friends who I know know what they are doing.

I would re-use my old stuff, just have it re-worked to specs. replacing what needed.

vs

buying a crate motor shipped to me, from an outift I had never done business.

vs

just buying a new truck

 

[rotwiler]

I bought a tuner used off here to turn off the mds on my 2013 5.7. Before the tuner I did the other way to turn it off, but this way I don't have to think about it and was cheap, plus the tune felt better overall. Hoping if constantly turned off it will avoid the mds issues. Thinking over the years oil pressure could be a issue with some 5.7s, my 13 oil pressure is always higher than almost every one I seen post here, I have no hemi tick, my oil pressure starts around 60 and varies, but goes up from there are rarely drops under 60 unless driving slow in town and come to abrupt stop.

 

[tones2SS]

Companies taking bids on whoever will supply parts for the cheapest price is not always conducive to getting a quality part/product.

Absolutely true!!!
Look at all the Hellcats that had supercharger issues in the past. Horrible

 

[OCDTech]

Sounds like I'll just keep switching it off then.

Can i ask if you have had any exhaust manifold bolts replaced? I have a theory, and only a theory at this point, that running for an extended period of time with MDS on, ( Two cylinders of fire shooting in the manifold, and two cold) ,may add to the stress of the heat difference in the manifold causing the bolts to break. If you haven't, may have saved you this headache as well. Haven't got to ask anyone whose run without MDS for so long. I bought my truck with 10,000 miles and have always run MDS off. And from what i read don't really think it saves much gas.

 

[RVGuy]

Can i ask if you have had any exhaust manifold bolts replaced? I have a theory, and only a theory at this point, that running for an extended period of time with MDS on, ( Two cylinders of fire shooting in the manifold, and two cold) ,may add to the stress of the heat difference in the manifold causing the bolts to break. If you haven't, may have saved you this headache as well. Haven't got to ask anyone whose run without MDS for so long. I bought my truck with 10,000 miles and have always run MDS off. And from what i read don't really think it saves much gas.

Just had my first bolt snap a couple weeks ago actually. I don't think it's the MDS, just dissimilar metals expanding and contracting at different rates causing stress on the bolts. Still though, they all lasted over 150k so I'm doing better than a lot of the other Hemis out there, maybe you're onto something?

 

[OCDTech]

I'm going to continue turning mine off, thank you.

 

[tones2SS]

I'm going to continue turning mine off, thank you.

Same here!!!
Every single time I use my truck, it comes off.