Signs and Symptoms of Bad MDS Solenoid (Explained)

When Chrysler came out with their Hemi engine, the whole driving game changed. Saving energy became very efficient as loss of heat was greatly reduced. The revolutionary Multi-Displacement System (MDS) provided the ability to deactivate cylinders when not in use, thus providing more power.

But like all mechanical workings, wear and tear are inevitable. Thus, it is important to look out for signs and symptoms of bad MDS solenoid so that you can resolve those quickly. Below are some distinct signs that show your MDS solenoid is failing.

Signs and Symptoms of Bad MDS Solenoid

Learning about these signs and symptoms will help you identify bad MDS easily.

1. Ticking Sounds

Drivers with Hemi engines are most familiar with this issue, and it is a definite sign that the MDS solenoid is failing. Constant ticking noises from the engine will fill the car while driving.

This is one of the more common symptoms, and it is likely caused by an exhaust leak. An exhaust leak happens when the exhaust fumes containing carbon monoxide and other poisonous gases enter the cabin instead of going out through the car’s tailpipe. Leaving this untreated will make driving the vehicle extremely dangerous.

You could try blocking the exhaust to confirm that the ticking noise is coming because of an exhaust leak. If the ticking gets louder, there is a leak for sure, and your MDS solenoid is going bad.

2. Internal Problem with Lifter

Sometimes the ticking sound will remain even after fixing the exhaust leak. This means that there is a deeper problem lying around which needs immediate attention.

One way to confirm is to check to see where exactly the ticking noise is coming from. If you hear the sound directly from the engine block, it is very likely that the car’s lifter is having issues.

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As MDS technology mostly revolves around the usage of cylinders, the solenoid is failing for sure if there are problems with the lifter. Providing enough lubrication in the cam lobe and replacing the spark plugs can help solve this problem.

However, you might need to replace the lifter altogether if the ticking noise does not go away.

Ticking noises may be the first sign, but a damaged lifter is an obvious sign that your vehicle’s MDS solenoid is bad.

3. Dropped Valve Seat

Unfortunately, Chrysler engines are prone to have dropped valve seats. The most common reason this occurs is due to heat dissipation issues. When air pockets enter the engine’s cooling system, the hot air accumulates inside and results in overheating.

The hot air then travels into the valve seats of the cylinder heads, causing them to drop. Driving with dropped valve seats in the engine can potentially damage the catalytic converter. Once again, this problem roots in a faulty MDS.

4. Short-Lived Misfiring

When the idling gets rough, and acceleration is slow, you may notice black exhaust fumes coming out of your car, and the engine will also make coughing noises. Also, if your engine code shows P0300 or P0312, it is evident that the engine is misfiring.

A misfire occurs when the engine cannot start up because the cylinder is unable to combust properly. When the oxygen, fuel, and sparks don’t come together at the same time to fire up the cylinder, the engine will falter.

The main issue with misfiring is usually because of faulty spark plugs and coil packs. But if your car has a Hemi engine, you already know what the culprit is.

5. Abrupt Turning on and Off of MDS

Most drivers with Hemi engine vehicles have noticed that the MDS just suddenly turns off and back on at random intervals, out of nowhere. A dirty throttle body is a common contributing factor as it is prone to having dirt and dust deposited in the air.

Underlying issues with the spark plugs can also make the MDS perform oddly. But the majority of the time, such behavior is caused by a bad MDS solenoid.

The problematic thing about this issue is that the MDS is responsible for four solenoids. And if it keeps turning on and off, it means that the cylinders are not working at the same time.

Hence, the only solution is to replace the whole MDS unit completely. It is a costly resolution but the only one you have to resort to.

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6. The Engine Coughs

Weird noises from the car will always feel alarming because you are never sure what is causing it and what the main problem is. And air circulation is crucial for the inner workings of an engine. So, most drivers like to install performance exhausts to keep the internal air clean and use less fuel.

Sometimes the engine makes loud noises after putting in a performance exhaust mainly because of loose connections of the components. But if you check and see that everything is proper and in place, you can point your finger at the MDS solenoid.

7. Lots of Buzzing and Vibration

It makes sense for your car to vibrate when going on bumpy roads, but what if the ground is smooth? A malfunctioning MDS solenoid will most likely cause your car to make loud buzzing noises and vibrate randomly.

The feeling is unpleasant, and the only way to get rid of it is to disable the MDS altogether. You can achieve this by using an appropriate tuner. A rather expensive way to solve this problem, but the only way, nonetheless.

How Do I Fix a Bad MDS Solenoid?

There are a couple of straightforward ways you can fix a bad MDS solenoid. They are provided as follows:

1. Fix the Exhaust Leaks

Your MDS solenoid can be dysfunctional because of a leaking exhaust. But the good news is that there is a very simple fix for this using FiberFix heat wrap. All you have to do is:

  • Clean out the exhaust pipe first.
  • Soak the FiberFix in water for about 40 seconds, and squeeze out any excess water.
  • Cover the hole in the exhaust and hold it tight in the specific leak area for a couple of minutes.
  • Take the metal tape and wind it around the heat wrap.
  • Run your car for about an hour after this process. 

2. Do an MDS Delete/Use Non-MDF Lifters

With the help of a tuner, you can “delete” the MDS by disabling it permanently. DiabloSport Tuner is a good choice for this purpose.

There are advantages to disabling the MDS, as it can give your vehicle maximum horsepower.

Switching to non-MDS lifters is also a suitable option. As MDS lifters cannot work without the corresponding solenoids, there will be no chance for MDS solenoids to go bad in the first place.

Additional equipment is needed to get non-MDS lifters, and the process can be lengthy. But in the long run, the solution will be worthwhile.     

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3. Replace the Solenoid

The steps to replacing the solenoid are rather technical and must be done with care and attention. There are video tutorials online that show detailed steps on how to remove and replace the MDS solenoids. But if you don’t want to risk doing it yourself, hand the job over to your car mechanic.

Frequently Asked Questions

Why are Hemi engines so popular?

Despite all the issues you have just read about regarding MDS solenoids, Hemi engines remain a very useful and reliable choice for drivers to this day. Hemi engines have proven to increase fuel economy and give full engine power.

What is so special about the MDS solenoid?

Vehicles have 4 to 8 cylinders, and the more cylinders there are, the better the performance is. But MDS shuts down 4 of the cylinders by turning off the fuel injectors and collapsing the valves for solenoids.

How do I disable MDS on Hemi?

You can disable the MDS by manually placing the shifter into the 5th gear. This will disable the MDS even though the process can be somewhat exhausting. But by using a DiabloSport tuner, you can permanently shut it off.

Is replacing an MDS solenoid expensive?

Yes, replacing an MDS solenoid is typically expensive because the components themselves are costly. The process itself is very technical and needs to be dealt with through expert hands; otherwise, there is a chance of the solenoid breaking. So, even if you have a car mechanic do it for you, the labor cost alone starts from $500.


Driving with a Chrysler Hemi engine can be tricky and challenging, but if you stay alert and take proper care of your car, all the issues can be overcome. Hence, it is of critical importance to pay attention to the signs and symptoms of bad MDS solenoid.

Knowing the base cause of the issue will help you solve the problem easier. Some of the fixes are quick, while some are expensive, but all worthwhile nevertheless. But if the problems are overwhelming, it is best to get rid of the MDS system altogether.  

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Brian Polk

Brian is an automotive expert who has 12 years of experience in the industry. He has worked on a variety of cars, from high-end luxury vehicles to budget-friendly options, and has a wealth of knowledge on the subject. He is passionate about automobile and enjoys sharing his knowledge with others, whether they are looking to purchase a new motorized vehicle or simply learn more about the inner workings of these machines. In his free time, Brian enjoys working in his automobile workshop and spending time at the track.

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