| Cylinder-Head Service -- Re-assembly and Compression Test |
From "Weekend Mechanic"
episode WKM-103 |
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Cylinder-Head Re-assembly
With the new gasket and cylinder head installed in the vehicle (figure A), the final installation procedures can get underway to complete this project. In this, the head is bolted in place to proper torque specifications, the manifold, push rods and rocker arms are installed and re-assembly is completed. Once the installation is complete, the engine is given a compression check to ensure that the repair has been effective.
Important : Included below are the steps in this automotive procedure as shown in the episode. These steps are general guidelines that are applicable to most vehicles. With any particular vehicle, there may be procedures, specifications, settings, tolerances, components, etc. that are specific to that vehicle. Always consult your vehicle's service manual when undertaking significant automotive repairs.
- The next step in the project is to tighten down the head bolts to secure the cylinder head on the block. This engine uses a torque-to-yield head bolt system, meaning that the torque-tightening for each bolt is done in three stages. Each bolt is tightened two steps using the torque wrench. The final stage is an additional 90-degree turn. In this type of system, head-bolts cannot be re-used, so new head bolts are installed.
- It's a good idea to lubricate the threads and washers of the head bolts (figure B) before installing them.
- Install the head bolts using the appropriate socket wrench (figure C), but don't tighten them down all the way.
- Once the bolts are installed, follow the torque specifications and diagram from your service manual (figure D) to tighten the bolts down using the torque-wrench (figure E). Torque in the proper sequence, then give each bolt a final 90-degree turn.
- Once all of the bolts have been installed to proper torque specs, the next step is to install the exhaust manifold. Install the replacement manifold gasket (figure F).
- Install the manifold, tightening down the bolts securely (figure G).
- Add some of the appropriate motor oil to the head (figure H) to prevent dry-start.
- Next, install the rocker arms (figure I). Install them in their original positions over the correct push rods.
- Re-connect the accessories and tighten down the rockers.
- Replace the valve-cover gasket with a new one (figure I).
- Install a replacement PCV (positive crank-case ventilation) valve. The old PCV valve simply pops out of the valve-cover. Remove the old one from the hose, replace it with a new one, re-insert it in the valve cover (figure J), and replace the lock-nut.
- Finally, replace the engine valve-cover (figure K). Set it in place gently to avoid tearing the new gasket. Making sure that it is properly aligned, secure the cover with the mounting bolts.
Engine Compression Check With the re-installation complete, the last step is to perform a compression test on the engine to verify the effectiveness of the repair. Cylinder-compression test-kits are available for about $120. The compression test will make sure that the new gasket sealed properly and that the new head and associated accessories are in good shape before the vehicle is taken back on the road.
- Follow the instructions that come with the kit. Remove the spark plugs, then connect the gauge and hose to one of the sparkplug holes.
- Have an assistant crank the engine and check the gauge readout (figure L) to ensure that the engine is holding the appropriate compression measured in PSI.
Provided that the compression test doesn't reveal any problems, take the car for a test drive.
RESOURCES :
The Complete Idiot's Guide to Trouble-Free Car Care
Author: Dan Ramsey
ISBN: 0028635833
Alpha Books
How Cars Work
Author: Tom Newton
ISBN: 0966862309
Publisher: Black Apple Press
Auto Repair for Dummies
Author: Deanna Sclar
ISBN: 0764550896
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