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As much as we love the Hemi, you’ve probably run into some 5.7 Hemi multi-displacement system problems. It doesn’t mean it’s a bad engine. It’s just like any other.
They’re far from being perfect, and from time to time, you’ll have to manually fix whatever comes your way.
With that in mind, we’ve spent hundreds of hours gathering the most common problems drivers might experience with MDS.
That said, are you ready to get your hands dirty and fix your truck? Let’s get right into it!
How does MDS work on the 5.7 Hemi?
MDS refers to the multi-displacement system. When turned on, this system is supposed to give the driver better gas mileage.
The Hemi 5.7 has eight cylinders, but some cylinders must be shut off to improve gas mileage.
That’s what the MDS does. So, once the system has turned off the four cylinders, you’re only left with eight.
However, the MDS does not work when towing. In fact, it’ll automatically be disabled. And as reliable as that system sounds, not every driver on earth enjoys it.
In fact, there are plenty of forums online talking about how to disable this annoying system.
The MDS can be problematic at times, and some of the issues drivers experience are meant to be “features,” including vibration and sometimes poor performance.
7 Common 5.7 Hemi MDS Problems
Now that you know how the multi-displacement system works let’s find out how to fix the vehicle.
That said, below, you’ll find plenty of issues with the Hemi 5.7 MDS and how you can fix them:
1. Ticking Noise
The infamous Hemi ticking sound. Perhaps one of the most notorious 5.7 Hemi multi-displacement system problems.
Usually, drivers take their vehicles to the dealer when they first hear this sound.
And surprisingly, most of them are quickly told that this issue is quite common on the Hemi 5.7.
Even if you don’t have it, there’s a high chance you’ll eventually run into this problem.
But let’s be honest, nobody wants to hear that. You paid for a vehicle, and now you’re stuck with a “feature.” Don’t worry, though.
Owners of this engine have determined this problem is caused by an exhaust leak.
To find out if it’s an exhaust leak, plug it up. Be careful, though. You don’t want to shove it all the way in.
After blocking the exhaust, the sound might become louder. This means that you have an exhaust leak.
But we got great news, fixing an exhaust leak is relatively easy and inexpensive. You don’t have to pay anybody, and you can do it on your own.
That being said, if you’ve set your mind to pull it off, follow these steps:
- First and foremost, get FiberFix heat wrap. Next up, get underneath the vehicle and then clean the exhaust using a wire brush.
- Now put your gloves on before unpacking the FiberFix heat wrap. It has resin, so your hands will get dirty.
- With that out of the way, use FiberFix heat wrap and put it in water for about 40 seconds. After that, squeeze any excess water.
- Next up, wrap the FiberFix heat wrap around the exhaust leak. Now squeeze the FiberFix so that the resin can do its job. Finally, cover the little metal tape around the FiberFix.
- Now hop in the car and start up the engine. Let the vehicle run for an hour. And that’s it, that’s a permanent fix.
See how easy that is? It doesn’t take as much time as you might think. And it’s pretty cheap compared to going to the local mechanic.
2. Lifter Problem
If you’ve successfully determined that you do not have an exhaust leak, then it might be an internal problem.
That being said, run this little test to find if the sound is coming from under the hood:
- Get a stethoscope to track down the noise. This is the easiest way, and it’ll save you so much time.
- After that, simply put the stethoscope on top of the engine. If it’s an internal problem, you’ll easily hear the noise coming from the engine block once you’ve put it on.
If the sound stays the same on the engine block, chances are you have an internal problem.
Finally, you should also watch out for engine codes. Here are some of the most common codes you’ll get if there’s something wrong with the engine:
If you get any of the above codes, please check the sparks first. They’re almost always the problem.
But, if replacing the spark plugs does not fix the issue, you’ve probably run into a severe issue. Perhaps the issue is related to the lifter.
When it breaks, it will blow the cam lobes. Typically, the lifters fail on the Hemi due to a lack of lubrication.
If lubrication is not reaching the cam lobe or the roller, the lifter will die on you. Undoubtedly, you’ll have to replace them to get rid of the noise.
We know that’s a lot of information, and it feels like going circles to some degree.
However, it’s always a great idea to explore every possible scenario before throwing parts at your vehicle.
If you want to learn more about this major flaw on the Hemi 5.7, watch this video:
3. DMS Problem
Every Hemi owner has a different take on the Dodge 5.7 Hemi displacement.
You’ll hear drivers talking about how great this system is and how efficient it is for saving fuel consumption.
But at the same time, you’ll run into drivers talking about how bad the DMS is and how they ruined the Hemi 5.7.
Generally speaking, there’s nothing wrong with the DMS. It runs pretty well and has been praised by countless consumers.
But if you genuinely suspect that it is screwing up your truck, you could turn it off.
First, you could get a Diablo tuner and disable it. That way, the truck will use eight cylinders. Alternatively, put the vehicle into the tow-haul mode or shift into fifth gear.
4. Dropped Valve Seat
The more googling you do, the more you’ll realize how common it is to have a valve seat drop on the Hemi.
Most commonly, the Hemi 4.7 and 3.7 are notoriously known for having this issue. But, it’s not just those two models.
This issue is often found on the Hemi 5.7 and other engines that use aluminum cylinder heads.
The easiest way to explain why this happens is due to air pockets. Inside the system, there are air pockets.
This shouldn’t happen. There shouldn’t be any air pockets inside the cooling system.
And when you don’t bleed the air pockets out of the system, you’ll get super-heated air moving around the valve seat.
Eventually, the hot air will move the valve seat. So, to get the truck back in great shape, replace the valve seat.
5. MDS Turning On And Off
One problem that we’ve seen drivers point out from time to time is that the MDS turns on and off randomly.
Generally speaking, this is caused by the 5.7 Hemi multi-displacement solenoid.
There are also other symptoms you should watch out for, including hesitation, stall, and shutter.
But before jumping to any conclusions, you must keep in mind that there are many if not hundreds of reasons why your car might stall and shutter.
For instance, when was the last time you cleaned the throttle body?
A dirty throttle body will cause rough idle. Keep in mind that it regulates how much air goes inside the engine. And when it’s dirty, the engine can’t breathe out.
And what about the spark plugs? When was the last time you changed them? They’re just as important as the throttle body.
But like we said before, in most cases, this is related to the MDS solenoid. When it fails, the system will shut off and off.
Keep in mind that the MDS is in charge of 4 solenoids. They are responsible for sending oil pressure to stop the valves when the MDS is running.
If the solenoid were to get damaged, the valves would run like they always do, but the only difference is that the cylinder is not working simultaneously.
So, to get rid of that problem, you’ll have to replace the unit itself.
6. Obnoxious Noise
We know pretty well how obnoxious Hemi multi-displacement problems can be, especially when it’s your vehicle making those unbearable noises.
But it doesn’t always mean that there’s something wrong with the car itself. Perhaps that noise is nothing to worry about.
With that in mind, we’ve noticed that several drivers have complained that their trucks sound pretty annoying after installing a performance exhaust.
If you’ve recently installed one of those, that’s most likely the culprit.
Now, you have two options here. You could reinstall the old exhaust, or you could give up on some fuel economy.
The sound is not harmful at all, but it’s up to you if you want to stick with it.
If there’s one thing Dodge owners hate about the multi-displacement system is that their vehicle randomly vibrates when going down the road.
That reason alone has made drivers hate the MDS. Think about it; that’s incredibly frustrating.
However, this only happens when the MDS kicks in. Still, it’s super frustrating.
And like we explained earlier, you’ll have to get a tuner to turn off the MDS if you’re having problems with it.
That’s the only way to get rid of the system for good. The mod is somewhat expensive, but it’s worth the money if you want your ride to improve.
But if getting a tuner is out of the question, you could put the truck in tow mode for the time being.
That will disable the MDS, though keep in mind that this is just a temporal bypass until you can get a tuner. As soon as you turn off the tow mode, the MDS will kick in.
Frequently Asked Questions (FAQs)
As much as we’d like to cover everything about this engine, there’s only so much we can do. To make up for that, here’s a section with several common questions about the Hemi 5.7:
Is Hemi engine reliable?
Definitely, the Hemi 5.7 is still to this day the go-to for many drivers. This engine has proved since its release to be one of the most reliable engines in the market.
Can you disable MDS on Hemi?
Yes, you can turn MDS off. But here’s the thing shifting into fifth gear might be annoying for most drivers. Instead, get a Diablo tuner and permanently turn it off.
Is MDS bad for the engine?
No, the MDS is not bad for your engine. The whole idea behind this system to actually to improve fuel efficiency.
The only complaint about the MDS is that drivers can only use four cylinders instead of eight. But you can quickly get around that.
How to know when MDS is working?
Keep in mind that when MDS kicks in, no dashboard tells the driver it is on. In fact, drivers can only tell that MDS is running by “feeling” the engine.
The engine will sound different than it usually does. Also, the RPMs might drop when the MDS is working.
That was a lot of information, wasn’t it? Hopefully, you managed to track down the 5.7 Hemi multi-displacement system problems.
As you could tell, finding the root of the problem is pretty straightforward. They might take some time if you’ve never done anything like this before, but that’s about it.
Finally, don’t forget that you can disable the MDS if you hate the system.
Shift into fifth gear, and that’s it. But if you want to forget that it’s even a thing, install a tuner, and it’ll be gone permanently.