This bad valve day started with a blinking/flashing check engine light. The owner reported that the engine started to run rough, and the check engine light was flashing, “We were only a few miles from home, and just as we got to our house the engine started to run real rough. Do you think it would be safe to drive it out to your shop?”.
Not a good idea to drive
We never suggest driving a vehicle with a flashing check engine light, so that of course was not recommended to this customer. A short time later the phone rang again – “We’re having AAA towing bring the van to you. We thought we were going to drive it but its now making a bad noise!” Once off the tow truck, our tech turned the key to start the engine, then could not turn it off fast enough – the noise could be heard inside the shop!!
Our tow car is a highly modified Chevy. Modified as in the front and rear bumpers have been drilled to allow for a chain to be looped through, which allows us to hook a tow chain to a vehicle to bring it into the shop without hurting someone’s back or damaging the vehicle. Once the crippled Town & Country van was in the shop, a scan tool was connected to the vehicle’s diagnostic data port. Link to Free Loaner Cars
As much as people complain about the computers in today’s cars, they can be helpful with the time saving information they provide. We knew there were internal problems but there is a lot stuffed under the hood of today’s vehicles, so having an idea of where to look is very helpful and saves time. The computer reported a code of P0303, which means there was a misfire occurring in cylinder #3 – now we have a better idea of where to start.
Cylinder #3 just happens to be at what we would call the back of the motor, and the misfiring cylinder was closest to the firewall, so you have less room to work and have to bend over further. As you look at the engine compartment image above and compare to the image to the left, you can tell getting to that spot is easier said than done, just getting to the rear valve cover takes time.
With the valve cover removed, the cause for the misfire was found: a broken valve spring, which can cause an engine to skip/misfire. The sad part is if the driver had shut the engine off as soon as the check engine light started flashing and had the vehicle towed at that point, it’s possible that they would have saved a lot of money.
The job of a valve spring is to hold the intake and exhaust valves shut. A lobe on the camshaft opens the valve via a lifter, push rod and rocker arm, all to let air & fuel in and exhaust gases out. When a valve spring breaks, it no longer holds the valve closed as it should. In this case the valve spring was still holding well enough for the engine to run, but as they continued to drive the vehicle the broken up section started riding down the spiral of the spring. Once enough tension was gone, the valve keepers that lock the assembly together fell apart.
Valve keepers or locks, are a very small part with a big job. When valve keepers fall out, the valve is allowed drop out of the cylinder head and into the cylinder.
The valve train assembly
To the left you can see an example of the valve train assembly, and the location of the valve keepers/locks. A good valve spring has more than enough tension to keep the keepers in place. But once you reduce that spring tension, pieces start to fall apart. Click on image for a better view of the assembly.
We know that with a broken valve spring and no valve in sight that the prognosis for the Town & Country was not looking good.
We had a pretty good idea of what we would be seeing when we removed the cylinder head – just didn’t think it would look this bad. In the image to the left you can see that the exhaust valve is missing and the cylinder head was pretty banged up.
Just had to look down to see the extent of the damage caused to the engine. With the engine running, the valve had dropped down into the cylinder. Because the other 5 cylinders were making power, cylinder #3 was pounding away at the exhaust valve. An aluminum piston can’t stand up to the valve but it put up a great fight. The piston managed to break the valve into pieces. The only part we could see was the head of the valve protruding from the piston – the remains must have been down in the oil pan via the hole in the piston.
Bad valve day, equals bad engine
This Chrysler Town & Country was a low mileage vehicle that had not been driven in the winter salt, what we call a real clean car. Unfortunately for the owners the damage was too extensive to repair, and a replacement engine was needed. Sadly we were not able to find an engine with mileage as low – the replacement engine had an additional 60k on it.
In the end, if the customer had just turned the engine off we could have easily replaced the broken valve spring. Instead we replaced the engine.
The next time you have a flashing check engine light, don’t think “maybe I can get it home”. This is just another example of why even your owners manual says “DON’T DRIVE THE VEHICLE” with a flashing check engine light! Or…. you too might have a bad valve day.
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