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Tag: cylinder head

Why Is My Diesel Cylinder Head Cracked? 4 Common Causes And Prevention

A damaged cylinder head can be devastating to your engine—and your wallet. And sometimes it’s not just your cylinder head that has an issue. It can be an indication of larger engine problems.

If the damage is not too extreme, there might be a chance to repair the existing head, but, in many cases it will need to be replaced.

One of the most common causes of cylinder head failure is cracking. This will most likely cause you to need a replacement head, because machine shops aren’t always able to repair them very well. This causes the cracks to reoccur soon after a rebuild, putting you in the exact same position, but out the money for the initial repair.

Frequently, cracks appear between the valves, one of the weaker spots on the head, but that’s not always the case. The operating conditions play a large role in how the damage occurs on the cylinder head.

CAUSES OF A CRACKED CYLINDER HEAD

1. OVERHEATING

The most common cause of cylinder head cracking is overheating. The rapid heating of the engine causes the head to expand and then contract as the engine cools. This puts a large amount of stress on the cylinder head, leading to cracks.

2. STRESSFUL OPERATING CONDITIONS

Similarly, stressful operating conditions can lead to cracks, along with other engine problems. This is especially true if you have an engine model where your engine block and cylinder head are made of different materials.

A common combination is a cast iron block and aluminum head. The two metals expand and contract at different rates, causing cracks in the lighter aluminum head more quickly.

3. LINER DROPPING

Often, when the head gasket blows, it may be due to the liner “dropping” in the block. This will release the tension holding the head gasket and allow the compression gasses by.

It’s also possible that when the compression enters the cooling system, it could displace the coolant, causing the cylinder head to overheat significantly.

4. HOW CAN YOU PREVENT A CRACKED CYLINDER HEAD?

Keeping your engine from overheating can help, so it’s important to keep a close eye on your coolant levels. Small preventative measures like this can really save you a lot of money down the road.

ISSUES CAUSED BY CYLINDER HEAD CRACKS

A number of issues can arise from a cracked cylinder head.

1. COOLANT ENTERING THE CYLINDERS

Coolant can enter the cylinders and engine block through the crack. This can contaminate the oil, causing other major engine problems.

It could also cause pitting and damage to the engine block. If the coolant enters the cylinder itself, it is often burned off in the exhaust, while damaging the cylinders. If this damage occurs, it’s likely that more than just the head and head gasket will need to be replaced to regain a proper seal for combustion and prevent further damage.

2. VALVE DAMAGE

Depending on their location, cracks can also cause damage to the valves. This will decrease your engine efficiency, and can also lead to further problems later on.

When Can I Reuse My Cylinder Head Bolts? How To Clean, And Inspect

Head bolts might seem like a minor or unimportant part, but without them, combustion wouldn’t be possible and your diesel engine wouldn’t work. They hold your cylinder head to the engine block and help the head gasket to seal properly.

When you take apart or replace these components, you shouldn’t ignore your head bolts. Doing so could increase your risk of serious failure down the road.

The initial temptation might be to just reuse your old head bolts. I mean, how bad could it really be? At times, this might be completely fine, but as we’ll go on to discuss, it may not be in your engine’s best interest to put old bolts back in.

So, just how do you tell when it’s safe to reuse your bolts? We’re taking you through when you might want to consider replacing your head bolts.

INSPECTING AND CLEANING YOUR HEAD BOLTS

After you remove your head bolts, you’ll want to give them a solid inspection before deciding whether or not to reuse them.

WHAT TO LOOK FOR WHEN INSPECTING YOUR HEAD BOLTS

First, check for any obvious signs of wear or damage to your bolts. Especially pay attention to the threads. Worn or damaged bolts stand a much higher chance of failure.

Check the length of your bolts as well—if your bolts have been too stretched, they will have lengthened. They will likely display some visible distortions because of this.

You should also always check the length of new bolts, as depending on your engine model, different bolt holes require different length bolts. The wrong length bolts won’t clamp down with the correct force, which affects the seal and allows for leaks.

THINGS TO KEEP IN MIND WHEN CLEANING YOUR HEAD BOLTS

The bolts and bolt holes need to be completely cleaned before reinstallation to ensure proper clamp and torque measurements. Lubricate the bolts in engine oil as part of the cleaning process.

3 SIGNS YOUR HEAD BOLTS CAN’T BE REUSED

1. DAMAGED HEAD BOLTS

Bolts with any signs of damage, no matter how slight, should never be reused. Not only will the bolts eventually fail, but when they do, there is the potential for them to cause damage to your cylinder head. This results in a much more expensive repair than simply replacing the bolts in the first place.

2. STRETCHED HEAD BOLTS

Bolts are designed to stretch as you torque them into place, and when you remove them, they snap back to their original position. Because of this, many standard head bolts are okay to use more than once, as long as they have not been stretched past their spring back point. Once this occurs, they should no longer be used in the engine, as they won’t clamp properly.

3. TORQUE-TO-YIELD HEAD BOLTS

Torque-to-Yield bolts (TTY), should not be used more than once, because, by design, they are stretched past their spring back point the first time they are installed. This allows for a more even load, and is especially useful for some of the gaskets and cylinder heads made out of less forgiving materials.

Because they are stretched out the first time, though, it’s highly likely that they will fail if reinstalled, due to overstretching and improper clamping. If you’re unsure whether or not you have TTY bolts in your engine, check the specifications in your engine manual, which should tell you.

PROBLEMS WITH REUSING HEAD BOLTS

An old head bolt that doesn’t allow for proper clamping can lead to leaks in your engine. Coolant will be able to leak through the bolt hole and cause more issues for your engine.

One of the largest issues with reusing old head bolts that are past their prime is the risk it creates for your gasket. If a head bolt breaks or fails to maintain torque, you can blow the head gasket, which in turn leads to a whole host of other issues for your engine—and an expensive repair.

Similarly, you won’t be able to install worn or damaged bolts correctly, which impacts how the gasket is installed. A poorly installed gasket leaks and can damage other engine components.

All in all, it’s often best to install new head bolts when you work on your cylinder head or head gasket, unless you can be absolutely sure the age and condition of your current ones. It will save you headaches and cash in the future.

Warped Or Pitted Diesel Cylinder Head? What’S Next? Failure Analysis

As we’ve mentioned in a previous post, cylinder head damage is a major issue that can cause problems throughout your engine. It’s not just cracks that you have to worry about.

Both warped and pitted or corroded heads can cause just as much damage, and can masquerade as issues with your head gasket. Both problems create sealing issues, which lead to leaks and other damage.

That’s why it’s so important to always find the reason your gasket failed. It doesn’t usually just happen on its own.

WARPED CYLINDER HEADS

Warping of the cylinder head is caused by conditions similar to cracking, namely overheating. When a head is heated past normal operating temperatures, it expands past its limits.

As it cools, the head often will not return to its original size or shape, instead settling into a more bent or distorted form. Repeated too many times and this will cause cracks in the head.

WHAT’S WRONG WITH A WARPED CYLINDER HEAD?

A warped head is dangerous for more than being a precursor to cracks, though. It will eventually cause gasket failure, and depending on the amount of warpage, can allow for leaks.

WHAT TO DO IF YOUR CYLINDER HEAD IS WARPED

The cylinder head should, at the very least, be reground flat to regain a good seal, but it’s likely that it will need to be replaced altogether, especially if the head is quite warped. If it’s not addressed, it will continue to damage your head gasket and cause further engine damage.

A straightedge and a feeler blade are used to help tell if a cylinder head has warped beyond being usable. Depending on the engine type, some warp is fine, but the range varies. Ideally, the cylinder head will sit flat on the gasket, creating a tight seal for combustion.

PITTED OR CORRODED CYLINDER HEADS

Similarly, a heavily pitted head will not seal correctly. A severely damaged surface will need to be replaced to maintain a proper seal for combustion.

Corrosion can both be caused by cooling system issues, as well as lead to increased problems with the cooling system. The corrosion/pitting can allow for coolant to leak into the cylinders, causing increased engine damage, oil contamination, and leading to more pitting, particularly on the engine block.

WHY YOU SHOULD PAY ATTENTION TO THE HEALTH OF YOUR CYLINDER HEAD

If these problems are severe and the seal between the head and gasket is poor, you can end up with even more engine problems. The poor seal will not allow for proper combustion, impacting your engine’s performance.

Oil and coolant can leak out of the head and the two can mix together, rather than keeping them contained to their proper channels. Oil could also leak into the combustion chamber, affecting efficiency and leading to higher oil consumption.

OTHER ISSUES YOU MIGHT NOTICE IN YOUR CYLINDER HEAD

These issues, since they affect the head gasket so much, can often point to gasket issues alone, but that’s rarely the case. If you’re having a gasket issue, you’re probably experiencing other problems as well.

That’s why it’s important to be able to identify the actual cause of the issue, otherwise you’ll continually be spending money on new gaskets while the real issues become worse and worse.

If you’re experiencing a warped or pitted cylinder head, it might be time to consider a new one, especially as a machine shop often will not be able to repair a more seriously damaged head.

6 Common Mistakes Installing A Diesel Engine Cylinder Head

It’s no small undertaking to replace your cylinder head, and it only makes sense that you want it done correctly. Ensure yours is properly installed with these guidelines and common mistakes to avoid.

Keep in mind that these are only general guidelines, and you should refer to your manufacturer’s instructions for more specific information on your engine type. To learn more about indicators you should replace your cylinder head, read our blog post, Signs You Need to Replace Your Cylinder Head.

If you’re looking for a new cylinder head, Highway & Heavy Parts has a wide selection, and our team of experts can help you get the right parts for your engine!

6 MOST COMMON CYLINDER HEAD INSTALLATION MISTAKES

1. YOU DIDN’T CLEAN THE BLOCK AND COMPONENTS

First, be sure the engine block has been completely cleaned. Any dirt or debris can damage components during operation. You should also clean any additional components prior to install to keep debris from circulating through your engine and creating larger problems.

2. YOU DIDN’T INSTALL DOWEL PINS

Tap the dowel pins into place on the engine block. Be sure to check for burring on the pins, which could lead to later problems.

3. YOU DIDN’T INSTALL THE HEAD GASKET

Check the manufacturer’s instructions to correctly orient the head gasket on the engine block. Improperly positioned gaskets won’t seal correctly and can create combustion issues.

Make sure the bolt holes are completely clean as well. Position the gasket on the engine block, most likely without any sealant or adhesive. (This depends on the gasket material, but most do not need it.)

4. YOU DIDN’T POSITION THE CYLINDER HEAD

Lower the cylinder head evenly into position on the alignment dowels to avoid damaging the head.

5. YOU DIDN’T INSTALL HEAD BOLTS

Ensure that the bolts are clean, the proper length, and free of wear. Be sure to follow the recommended torque guidelines.

6. YOU DIDN’T INSTALL REMAINING COMPONENTS

Following instructions for your engine type, reinstall the remaining components to the head as needed for your specific model. For instance, push rods, rocker arm assembly, camshaft, etc.

INCORRECTLY INSTALLED CYLINDER HEAD COMPONENTS

Installing your cylinder head and related components incorrectly could result in further damage to your engine. Here are some common mistakes you should avoid:

INSTALLING WORN FASTENERS

Be sure to evaluate your fasteners when you’re deciding whether or not to reuse them. Wear or pitting on the bolts can lead to failure, so look for any sign of that.

Even inspect new fasteners, as installing them bent or warped can create just as many problems. You want your fasteners to be straight, as free of wear as possible, and the proper length to ensure that everything fits together as it should.

Make sure that your bolts have not stretched beyond their limit, and don’t ever reuse bolts that are one time use only.

USING SEALANT ON THE GASKET

Most gaskets nowadays don’t require the use of sealant. Depending on the type, sealer could cause the gasket to deteriorate and fail.

HEAD GASKET SEALS

Ensure that the head gasket seals properly. A leak in the head gasket can allow oil into the cylinders, leading to high oil consumption in your engine.

Paying attention to orientation marks and manufacturer instructions can help with this. Make sure your liner protrusion has been checked and is in spec before installing the head.

Incorrect liner protrusion may lead to premature head gasket failure and possibly another cylinder head replacement.

If you’re experiencing cylinder head problems, Highway & Heavy Parts can help!

We carry only the highest quality diesel engine parts from the most reputable manufacturers, and we have ASE Certified Technicians on staff to help you.

Ordering from us is fast and convenient—you can call or shop online. And we have a huge inventory of replacement parts to help keep your engine running like it should!

With industry leading warranties and shipping of two days or less on most parts, Highway & Heavy Parts is here for you!

How to Install a Diesel Cylinder Head

A diesel cylinder head has multiple functions. It serves as the top seal for the engine cylinder. It also contains the cylinder intake and exhaust valves that manage engine breathing. Here’s how you can install the cylinder head.

Step 1 – Get Started

First, clean the cylinder head and the gasket surface of the cylinder block. Also remove any kind of oil or dust particles that can be clogging the threads of the head bolts or the bolt holes with the help of a thread chaser. Use a solvent to remove those old deposits using a plastic or wooden scraper.

Step 2 – Install the Gasket

Check the gasket surface of the cylinder head and the block for any warpage. Place the new gasket on the block and install the head assembly. Make sure that you do not rub or slide the cylinder head across the block, as there are locating pins on the blocks. Ensure that a new gasket is used that has not been compressed previously by using tightening bolts, as a cylinder head gasket gives a strong seal only once. Make sure that the new gasket matches the one it replaces. Now, install the pushrods and the rocker assembly. Then position the crankshaft to the TDC marking.

Step 3 – Tighten the Bolts

Make sure that the cylinder head is placed in proper alignment with the cylinder block. Tighten the cylinder head bolts by following the proper torque sequence. It should be noted that while tightening the bolts an initial torque and a final torque should be applied.

Step 4 – Install the Camshafts

Using a new gasket, install a new intake manifold and tighten the retainers accordingly. Now, place the camshafts on the cylinder head blocks and align the bearing caps over it. Tighten the bearing caps bolt in stages applying torque from center onwards.

Next, with a driving tool, carefully place the new oil seals into position. Install the No. 4 timing cover and the timing pulleys onto the camshaft. Make sure that the matchmakers and pins are in alignment. Rotate the engine till the matchmakers align.

Step 5 – Connect the Wiring

Connect the coolant hoses from the outlet on the front of the cylinder head and from the heater outlet on the left end of the cylinder head. Connect the wires joining the temperature and pressure sending units. Tighten the alternator mounting bolts and install the upper alternator bolts. Install the exhaust manifold. Connect the exhaust bracket from the exhaust pipe and the wire from glow plug bus. Also connect the accelerator cable and fuel injection pipes.

Finally, connect the negative terminal of the battery and the ground strap from the cylinder head or the intake manifold. If you are not sure about the connections, most user manuals come with wiring diagrams. Install the engine undercover.

Step 6 – Do Final Checks

Once again go through the entire setup and recheck if all the components are tightly held. Refill the cooling system and run the engine till it reaches the optimum operating temperature.