Honda DOHC Non-VTEC Rocker Cover Gasket and Cam Plug Reseal
Introduction
Oil weeping down the upper block, grime around the cam cover, or unexplained oil consumption on a Honda engine past 100,000 km is very often a failed rocker cover gasket or camshaft end plug (cam plug). This procedure reseals every upper gasket and O-ring on the head: the rocker cover gasket, the spark plug tube O-rings, and the notorious rubber cam plug behind the exhaust camshaft end holder. A leaking cam plug can contribute to significant oil loss over time, so a full reseal is the proper fix rather than smearing sealant on the outside. The writeup was performed on a D16A8 and applies to Honda DOHC non-VTEC engines (D16A8, B18A, B18B); DOHC VTEC heads are about 95 percent the same process except the rail above the camshafts must also be unbolted before the cam end holder can come off, and SOHC rocker covers follow almost exactly the same principle. Note the forum title says "upper head gasket" but, as corrected in the replies, the part being replaced is the rocker (valve) cover gasket - the actual head gasket is not disturbed. Work on a cold engine, preferably after sitting overnight. Adapted from a community writeup by bennjamin on OzHonda (https://ozhonda.com/forum/showthread.php?22561-DIY-Upper-head-gaskets-replacement-reseal-(non-vtec-DOHC-engines)), including corrections from the follow-up discussion.
Reference
Tools Required
- 10mm socket with ratchet and extension
- Torque wrench (capable of 7.2 lb-ft / 9.8 Nm)
- Pliers
- Small flathead screwdriver
- Large flathead screwdriver (or wedge)
- Soft rubber or wooden mallet
- Fine blade or scraper for old sealant
- Clean rags
- Container for fasteners
Parts Required
-
Rocker cover gasket (new; replaces the old gasket, do not stack)
-
Camshaft end plug/seal (new, or cleaned original if in good condition)
-
Spark plug tube O-rings (new, or reused if serviceable)
-
Hondabond, Loctite, or equivalent gasket sealant
Safety Warnings
- ⚠ Only work on a cold engine, preferably after it has sat overnight.
- ⚠ Never strike the camshaft end holder hard - use only light taps with a soft mallet, or you risk damaging the holder or camshaft.
- ⚠ If you remove or inspect multiple cam holders, keep them in their original order and positions - they are not interchangeable.
- ⚠ Torque the cam holder and cover fasteners to specification (7.2 lb-ft / 9.8 Nm) in a criss-cross, two-step sequence; overtightening or uneven tightening can warp parts and cause new leaks.
Step-by-Step Instructions
1 Prepare and survey the cam cover fasteners
With the engine cold (ideally after sitting overnight), open the engine bay and identify every 10mm cap nut on the cam (rocker) cover. On the D16A8 used in the original writeup there are 10 studs/nuts in total; count yours before starting so none are missed.
2 Remove spark plug leads and the vacuum hose
Pull each spark plug lead off and set the leads aside, noting their order. Remove the breather/vacuum hose from the top of the cam cover: loosen its clip and slide it further up the hose, then grip the hose with pliers and carefully shimmy it off the inlet pipe.
3 Remove the cam cover nuts and upper timing belt cover
Undo each 10mm nut with the ratchet, finishing the last few turns by hand. Remove the two 10mm bolts securing the upper timing belt cover and lift the cover off. Then remove the last two 10mm studs, which sit right beside the timing belt. Place all fasteners in a container so none are lost.
4 Break the cam cover free and lift it off
Insert a large flathead screwdriver or wedge into the gap between the cam cover and the head, and gently lever at several different points around the perimeter until the cover breaks free of the old sealant. Lift the cover off slowly so the O-rings and rocker cover gasket are not dropped or lost, and set them aside separately.
5 Clean all old sealant from the sealing surfaces
Inspect the old gasket and the top of the head. Carefully remove any old sealant residue with a fine blade, then wipe the outer sealing edges with a clean rag to remove remaining oil and sealant. Clean surfaces are essential for the new seal to hold.
6 Unbolt the exhaust camshaft end holder
The exhaust camshaft's end holder (guide) sits at the head's extreme lower left-hand side; remove its four 10mm bolts. Crack each bolt loose in two stages: an initial pop with the ratchet, then unwind and remove by hand. On DOHC VTEC heads, the rail above the camshafts (held by a few additional 10mm nuts) must come off before this step.
7 Tap the cam holder loose and remove it
Using a medium rubber or wooden (soft) mallet, lightly tap the camshaft end holder on alternating sides to work it loose from the head. Do not strike it hard. Once loose, ease the holder off together with the oil guides, taking care not to scratch or dent any part.
8 Remove the cam plug and inspect the holder
Pull out the cam plug/seal. Either fit a new plug or thoroughly clean the original of oil and residue with a fresh rag, and clean the lower face of the cam holder. Check the underside of the holder for irregular wear: heavy scratching or marking can mean the holders were not torqued correctly, or can point to a more serious camshaft problem. If you inspect other cam holders, keep them strictly in their original order.
9 Seal and refit the cam plug and holder
Apply Hondabond or Loctite sealant to the cam seal and to the cam holder - on both sides of every metal surface that contacts the cam plug - to ensure a reliable seal. Position the holder back onto the head and camshaft in its correct orientation, confirm the seal has stayed seated (redo it if not), then lightly tap the holder down with the mallet until it sits firmly on the head. A little sealant or oil squeezing out at the edges is normal.
10 Apply sealant to the head and fit the O-rings
Apply a liberal bead of sealant along the edges of the head everywhere the rocker cover gasket makes contact (applying it to the head is easier than to the cover, per the author's follow-up). Replace or reuse the spark plug tube O-rings: apply sealant to the metal surface beneath each, then seat the O-rings on top.
11 Torque the cam holder bolts
Refit the four 10mm cam holder bolts finger tight, then torque them to 7.2 lb-ft (9.8 Nm) in a criss-cross pattern using a two-step sequence to prevent warping the holder.
12 Refit the cam cover and torque all fasteners
Run a finger along the new gasket to seat it fully in the cam cover groove, then lower the cover down onto the head. Working in a criss-cross pattern, tap the cover lightly until it sits flat and even. Tighten the two studs next to the timing belt (under the timing belt cover) first, then reinstall the timing belt cover with its two 10mm bolts, routing the throttle cable correctly, and refit the spark lead guides. Finger tighten all remaining nuts, then torque every nut and bolt to 7.2 lb-ft (9.8 Nm).
13 Reconnect, clean up, and monitor
Refit the spark plug leads into the correct spark plug tubes, reattach the vacuum hose to the top of the cam cover, and wipe around the gasket edge with a damp rag to remove excess sealant and oil. Over the next few days of normal running, watch the cam plug end: a very slight weep can be sealed with a small amount of sealant around the outside, but a persistent leak means the reseal should be redone.
Pro Tips
- 💡 DOHC VTEC heads are about 95 percent the same procedure - the only difference is removing the rail above the camshafts (a few extra 10mm nuts) before unbolting the cam end holder.
- 💡 The same principle covers SOHC rocker covers almost exactly.
- 💡 The new gasket fully replaces the old one - remove the old gasket from the rocker cover and discard it; never stack the new gasket on top.
- 💡 Spread the sealant on the head rather than on the rocker cover - it is easier and is how the original procedure was done.
- 💡 Simply smearing sealant on the outside of the cam plug is not a proper repair; sometimes the plug itself needs replacement, and resealing from inside saves hassle later.
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