Replacing The Seal On Your 1.6 Miata Oil Pan

If you're experiencing oil leaks in your 1.6 Miata, it's likely that the oil pan seal needs to be replaced. This can be a challenging task as it may require removing the engine and oil pan, which is a complex and time-consuming process. However, some creative individuals have shared their methods for replacing the oil pan seal without heavy lifting. Their approaches involve a range of tools and techniques, from prying and clamping to specific seal pullers and screwdrivers. It is important to thoroughly clean the surfaces, carefully apply sealant, and ensure proper alignment during the process. Before attempting any repairs, it is recommended to consult a trusted mechanic or a detailed guide specific to your vehicle's make and model.

Identify the source of the oil leak

Oil leaks are a common issue for Mazda Miata owners, and they can be frustrating and messy to deal with. To identify the source of an oil leak in your 1.6 Miata, there are several steps you can take:

First, check under the car for oil spots or puddles, especially when the car is parked. This will give you an initial indication of a potential leak. If you notice oil on the ground, the next step is to try to locate the source of the leak on the car.

Monitor the oil levels in your Miata. If you notice frequent drops in oil levels, this could be a sign of a leak. It is important to regularly check your oil levels as part of routine maintenance.

Inspect the engine for signs of oil leakage. Look for oil residue or wet areas around gaskets, seals, and the oil pan. Use a flashlight to get a better view of the engine and its components. Pay close attention to the following areas, as they are common leak points:

• Valve cover gasket
• PCV grommet and oil filler cap seal
• Timing belt cover area for cam and front main seal leaks
• Cam sensor O-ring (common in 1990-1997 models)
• Cam seal plug (1999-2005 models)
• Dipstick tube O-ring
• Rear main seal
• Oil pan

If you notice oil residue or wet areas in any of these locations, it is likely that you have found the source of your oil leak. At this point, it is important to clean the area thoroughly and run the engine to monitor for further leaks. This will help you confirm the exact source and make a plan for repair or replacement of the affected component.

Additionally, there are a few other components that are known to cause oil leaks in Miatas:

• Crank seal
• Cam seals
• Oil pan gaskets (front and rear)
• Oil pump cover gasket
• Dipstick seal

By following these steps and inspecting the common leak points, you should be able to identify the source of the oil leak in your 1.6 Miata. Once the source is identified, you can take the appropriate steps to repair or replace the affected component, ensuring your Miata runs smoothly and leak-free.

Remove the transmission, clutch bits and flywheel

To remove the transmission, clutch bits and flywheel, follow these steps:

First, make sure you have the right tools. You will need minimal hand tools and wrenches. If you have air tools, even better. Ensure you have all socket drive extensions and a universal drive. You will also need 6-point sockets for 14mm, 17mm and 19mm bolts on the bellhousing, flywheel, exhaust downpipe and any other tough bolts and nuts to minimize rounding them.

Next, raise the car to a height of 45cm (18") to allow enough room for tool leverage and to be able to remove the transmission from under the car. Remove the centre console and gear stick. If you want to refresh the turret oil, suck out the old oil with a length of clear plastic tube or a turkey baster. Clean the turret opening and cover with duct tape.

Now, drain the transmission oil. Spray all bellhousing and exhaust downpipe bolts with liquid wrench and wait for a few hours, preferably overnight. You can use WD40 for this.

For added safety, place a bigger jack under the differential while working under the car. Make sure the car is on a flat surface. Give the car a vigorous shake to ensure it is stable.

Before removing the gearbox, disconnect all wirings at the top. The wirings are held on the top by bent clips. Also, remove the speedo cable and tie it away with a piece of wire. Remove the centre differential drive shaft.

There are 11 bolts on the transmission bellhousing. Eight are 17mm and three are 14mm. Two of these bolts are nutted at the other end and can be very tight. You may need a wrench to hold the nut at the other end to loosen and tighten.

If you are not disturbing the CAS, the coil and the heater hoses, bolts 1 and 11 are reachable from below with a long extension and universal socket drive. Bolt 11 can only be accessed when you have the exhaust downpipe removed. Loosen both bolts from the top after removing the CAS, the heater hoses and the coil unit.

Bolt 10 goes through the exhaust holding bracket and is the longest and toughest to remove. You may need to use a cheater pipe and a fair bit of force.

If your heater hoses are old and hardened, you will need to replace them. Slice them off with a sharp utility knife to minimize bending the soft heater copper tubes. Make a slice along the copper tube and twist the hose off. Be careful not to slice or twist too hard as the copper is very soft.

If you prefer, you can also remove the CAS to loosen bolt 1 from the top. You may need to do this by feel and using a long extension and universal socket drive.

Bolts 4 and 5 above the clutch lever are nutted at the other end and can be very tough. You might need a wrench to hold the other end to stop them moving while removing.

Bolts 9 and 10 go through a bracket that holds the exhaust downpipe. Bolt 10 is the longest and can be tough to remove. Brace your right leg on the transmission tunnel and your upper body extended out from the left of the car to get extra swinging room and leverage using a cheater pipe on the socket drive.

Bolt 5 under the clutch lever and bolts 6 and 7 at the bottom are the easiest to remove. You have plenty of room to swing your socket drive or cheater pipe here.

Loop a piece of rope around the end of the gearbox and tie its ends loosely to a block of wood in the cabin. Remove the two very long 19mm bolts and one short 19mm bolt at the rear gearbox bracket from the PPF. The two long bolts are tight and you will need a cheater pipe. Once these three bolts are removed, tighten the ends of the rope in the cabin to hold the gearbox weight before attempting to disengage the gearbox at the bellhousing. Put the jack under the front of the gearbox to hold its weight while you attempt to lower it.

Now, remove the six bolts to reveal the front transmission oil seal. On installation, lightly apply a coat of high-temperature bearing grease to the required areas.

Note: Check the orientation of your old seal before removal. The new seal may not have the same markings, but the notch configuration should be the same.

Use an oil seal removal tool to remove the oil seal. Prying with a screwdriver risks damaging the sleeve. Try to start prying at the 12 o'clock, 11 o'clock or 1 o'clock position. If you do nick the sleeve, chances of oil leaking from those areas are lessened. Use the other end of a punch to tap in the new seal evenly.

Note the thin metal shim around the oil seal. Measure its tolerance and order a new one if needed. The front cover gasket should be replaced too. Make sure you apply gasket sealant before installing the new gasket.

Finally, if you have the car raised high enough, do a semi sit-up to eyeball the alignment before final tightening.

Remove the rear main seal carrier

To remove the rear main seal carrier, you must first remove the transmission, clutch bits, and flywheel. Then, make sure the lip seal is the source of the leak by cleaning all the oil off the surface and waiting 24 hours.

Once you've confirmed the source of the leak, remove the rear main seal carrier. This is the metal part surrounding the seal, with four bolt holes. Some people suggest working a knife behind it to remove the sealant, but prying with a seal puller is more effective. Most of the carrier sits flush with the engine, but there is a tiny lip to pry on the right side.

After removing the carrier, clean every last bit of sealant off the carrier and the surface around the crank on the engine, including the oil pan lip. Be careful not to scratch the crank. You can use a putty knife to get the sealant off, and a small screwdriver to scrape the sealant out of the crevices.

Now, you can remove the rear main seal. You will need to replace it with a new, soft, and pliable seal.

Clean the surface around the crank on the engine

To clean the surface around the crank on the engine, you'll want to be careful and thorough. You don't want to scratch the crank, so use a putty knife to clean every last bit of sealant off the carrier and the surface around the crank on the engine, including the oil pan lip. There are a few crevices in the carrier that have sealant too, so use a small screwdriver to scrape the sealant out. After every last bit of sealant has been removed, wipe the carrier surfaces down with brake cleaner.

You'll want to be sure to clean the oil passages in the crank. You can use a solvent like brake cleaner to help with this. A pinpoint blow gun will probably use less air and let you get into the holes. You can also use WD-40 or a spray oil/water displacement.

Before you start, it's a good idea to snap a picture of the engine. That way, if you forget how it goes back together, you can refer to the photo.

Test fit the new seal

To test fit the new seal, you'll need to understand how the carrier mates with the back of the engine. The carrier uses four M6 bolts: two shorter tapered ones at the top and two longer ones at the bottom. The bottom two bolt holes on the carrier have metal sleeves that protrude about 4mm behind the carrier. These sleeves fit into locating holes in the engine.

This means that until the holes are perfectly aligned, the carrier can't be flush with the engine—the sleeves will get in the way. To make matters worse, the lip seal has to be vertically compressed by about 80% for all the bolt holes to line up. Compressing the seal by hand is almost impossible.

To get the seal and carrier in place, you must apply enough downward force to compress the lip seal enough for the sleeves to line up with the holes, and then enough force forwards to push the sleeves into their holes. Throughout this process, you must also ensure that the lip seal stays in place and doesn't pop out from under the carrier.

At first, this may seem impossible—the downward pressure required to compress the lip is huge and not really possible by hand. But there is a way. It is possible to align one sleeve with its hole very easily by allowing the carrier to rotate a bit, meaning the seal isn't compressed. Of course, the other bolt holes will now be out of alignment, but this is just the start.

Get a bolt into that hole and tighten it just a little so the sleeve can't get out of its hole, but not enough to compress the whole area. Now take a small C-clamp and clamp the other end of the carrier to the oil pan. There are small lips on both that just about work. Tighten carefully. The clamp or the carrier will want to walk a bit, so apply pressure to make sure neither does. You'll find you can tighten the clamp to the point that the bolt holes now all line up.

Congratulations. Now tighten bolts into all the holes. Depending on your luck, the seal should be nicely compressed in place. The notch on the seal should still line up with the notch in the carrier, although it might bulge a little from the pressure behind it. The slightly flared "wings" at each end of the seal ideally shouldn't protrude at all, but mine did a little. The friction from pulling the carrier flush with the engine means that the seal might not move all the way with the carrier at the very ends—since there's no ridge to keep these ends in place. We will be using plenty of sealant in that area, though, so this isn't a huge concern. The ends of the seal seem to be primarily for ensuring there isn't a hard stop to the seal, rather than being a critical compressed part of the seal. They don't compress much anyway.

Frequently asked questions