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Keep in mind that Zcars do not have magic engines or engineering that resists breakdowns. They did have very well built engines and were simply laid out. But the age-gremlins that plague other cars also live here. And despite their performance, a great many moving parts in the engine, suspension and drivetrain are getting pretty tired. Here are some quirks and fixes that seem to plague many 1970-83 Zcars.
SELDOM NOTICED DISTRIBUTOR PROBLEM
When I started buying distributors at the junkyard, I started noticing a disturbing trend concerning the advance mechanism inside. This breaker plate is in all distributors and rotates the whole works in response to the vacuum solenoid. On Z’s it’s the large round plate you see directly beneath the rotor that holds all the “bits”. The point is that it has a round plastic cage sandwiched into it which holds several little ball bearings, so it can rotate smoothly. Well in every single distributor I’ve seen, this little cage is broken/crumbled/dried out, due I guess to engine heat, old age, and general use. This means the advance mechanism is either frozen, or badly off kilter. These were in cars ranging from well maintained models to beaters, but it was consistent. In other words, I would suspect that after 20 years, most distributors in street cars are not functioning well and may be ruining performance. „h the way to test yours is to take off the distributor cap, and while watching, suck hard on the vacuum hose leading to the dashpot on the side of the distributor. The plate should rotate clockwise smoothly about 1/2″, and snap back when you release pressure. If you can hear your breath hissing from the distributor, the vacuum solenoid is probably leaking. If the plate crunches, sticks or moves poorly, the cage in it is probably bad. You can take the plate out with the distributor in the car andf inspect it. Look on my performance page in the Ignition section for details. But there’s no way you can fix the plate if you find it’s in pieces, you have to replace it. I was able to buy a new advance mechanism plate for about $45 at the dealer. If you’re not handy, buy a rebuilt distributor from Victoria British.
OIL PRESSURE GAUGE READS LOW AT IDLE
If your oil gauge starts reading zero at idle, don’t freak and start tearing into the motor. It’s almost always the oil pressure sensor on the right side of the block. Nissan makes great motors but can’t manufacture these, they seem to fail every few months. About $20 to replace. There are 2 types though: bullet lug connector (early Z) and double spade connector (late Z). Everyone always wants to blame the oil pump, but I’ve never heard of one wearing out on a Z. Keep in mind the cheap one from the auto parts store down the block may be inaccurate too.
CLUNKING REAR END
This is the bane of all Zcars, it’s almost impossible to completely fix. It can have many causes, but is almost never caused by the differential itself, especially if it’s an R-200. The following are all the places the clunking can exist: „h worn out mustache bar bushings (replace with urethane) „h u-joints on the halfshaft ends are loose and worn-out (common, replace them) „h tighten all the mounting bolts/nuts on both ends of the halfshafts „h front differential mount broken (try tightening the 14mm nut in the bottom first) „h driveshaft bolts loose „h ball bearings/grooves in halfshaft body worn (replace halfshaft) „h tighten the two large nuts that hold the differential to the mustache bar „h shocks bad or loose in strut I personally think most of the time it’s caused by the mustache bar bushings. These thin rubber bushings rot and flex and let the bar clunk the floor on acceleration.
ENGINE FAN CLUTCH SEIZES
Rather than spend bucks on a new or rebuilt one, fix it yourself. Simply take it off the car, unbolt the two halves, tap them apart, spray it out with brake cleaner, and refill the deeper half with 90 weight gear oil. The original oil dries/leaks out over the years. But don’t worry, it’s not full of springs or anything, it a simple design and bolts back up easily. Did it on mine and it went from almost seized to spinning freely. A better fix is to simply take the whole assembly completely off. You can then add electric fans on the radiator. This will free up a couple of horsepower, and make the engine rev much more quietly.
WET FLOORS
This could be caused by a leaky heater core, but mainly is caused by rain water. The rain gutter channels it down the front of the door sill (check the condition of your door edge gasket), or it also drips from the bottom corner of the windshield. What I can’t figure out is how it does it so invisibly, and ends up pooled under the mat.
Worse, the brown jute padding that Datsun used holds water like a sponge. No wonder so many Z floors have completely rusted through. I think this probably the worst Z problem. Everyone blames road salt for rusted floorboards, but this does it faster. What makes it worse it that it’s preventable. #@!&%! I have to dry my floor out every time it rains!
GROWLING FROM REAR AROUND 70 MPH
This is usually due to a worn out rear joint on the driveshaft. Go under and twist the joint where it bolts to the differential. There should be NO slight clicking or play, but after 20+ years it’s gotta go sometime. The manuals and catalogs will tell you that the joint “isn’t replaceable”. Well of course it is (!) What they mean to say is that Datsun didn’t make replacement U-joints for the 280. So instead of spending big bucks on a new driveshaft, just look in the yellow pages and take it to a driveshaft repair shop. I guarantee you they can replace the joint and rebalance it. Usually about $100.
EXHAUST/GAS FUMES EVERYWHERE
Beautiful car, but with terrible aerodynamics on the rear. The shape basically sucks up and billows exhaust around the back. Opening the windows causes low pressure in the car and sucks it in. Aside from checking all the seals around the hatch, check these in order of importance: „h the gaskets around the taillights „h make sure the both PCV hoses are connected. I used a small K&N filter on my valve cover for a year. Then I realized that the valve cover vents on low vacuum. No wonder spirited driving left the car smelling like a truck. Putting the hose back on helped. „h sounds simple, but make sure the exhaust system from cylinder head to tailpipe isn’t leaking. My header was cracked at the weld where it entered the exhaust pipe. „h check the firewall for missing throttle boots, gaps around heater hoses, etc. I had two holes from my missing A/C hoses which I found were pouring in gas fumes. „h Secure and seal the vinyl panel on the inside of the hatch. This made a big difference on mine as the emblem holes in the hatch were leaking a lot in. „h On early 240s, on the inside where the sides of the rear deck meets the fender, there can be a precise 1/16″ gap. This is where the panels meet, and they apparently didn’t seal the seams back then (I could see the road through mine) So I used silicone sealer to seal them and it helped a lot. „h If yours has a gas vapor tank in the right/rear fenderwell, spend an afternoon replacing all the hoses with new ones. Also drain and drop the gas tank and replace the 2 large vent hoses. But don’t spend $$ for the old fashioned braided types from Nissan, just buy good quality gas hose from an auto store. But DONT scrimp and use heater hose, the gas will eat right through it. The large vent on the drivers-side edge of 240 gas tank leaks a lot of fumes, and can be capped off with no problems. The associated vent on the vapor tank should be capped too. „h If your rocker panels are rusted from behind, air can filter in through the “swiss cheese” holes stamped into the door sills under the carpet. The left rear fender on some cars also has a rubber plug on the bottom which can leak air in.
SUSPENSION CLUNKING ON BUMPS
I read about this in the Z newsgroup and found it to be true. I would get a strange “clunk” from the rear when I hit a bump. It sounded like the spare tire was loose, but I couldn’t track it down. It turns out the “gland nut” or cap holding the strut inserts in was several turns loose. It was letting the insert clunk up and down in the strut housing. This can happen at all 4-corners, a pair of large pliers slipped between the coils makes this a quick fix.
CLOCK STOPS
These little fellows have spinning gears just like an old mantle clock. I have a feeling that the gears get gummed up over the decades. Mine recently slowed way down, so I plan on taking it out and cleaning/lubing it up.
RUST
Does anything need to be said? Rustoleum Rust-Converter seems to work pretty well for me, just brush it on and it converts the rust to a hard black finish.
TACH “JUMPS” OCCASIONALLY (later Z’s) This may be the coil, but I think I found the real cause. Note that the only thing that makes the tach needle move at all, is a pulse to the tach sensor wire. 260/280 tach sensors are connected directly to the negative terminal on the coil, while 240 tachs are isolated and use an odd inductive wire loop which triggers the tach. So for the tach to jump, something has to be affecting the pulse. Now on ’75-78′s, the – coil terminal sends 14v impulses out, which triggers the tach. And at one point, my 240s regulator failed and started putting out spikes of 17-19 volts. And when my ammeter needle jumped, so did the tach. That’s when I realized that any excess voltage in the tach sensor wire causes it to jump. So apparently these “jolts” you see sometimes are the regulator hiccuping. TIP: if your 240 tach is getting old, you can easily upgrade to a ’75-78 tach. All you have to do is remove the 280 “works”, and transplant them into a 240 metal housing and plastic front. The faceplate can be swapped to keep the redline stock. Make sure you run a separate wire with the resistor directly to the coil’s – terminal. Note that the + and – power leads on the tach are reversed. Easy and accurate.
KEY STARTS ERRATICALLY This is when the key has to be clicked several times to get the starter to turn, etc. It could be the starter solonoid, but if changing the starter is doesn’t work, it’s probably the black plastic ignition switch behind it the key lock. It’s held by two small screws, easily replaced with a screwdriver. $15 last time I checked.
FUSES KEEP MELTING (240z) Plagued by melting fuse wires, redhot fuses? Well, the 240 fusebox uses simple rivets and crimped wires to hold the clip-plates together. These contact areas oxidize over the years and increase resistance in the connections. Through such a marginal connection, current draw goes way up and so does the temperature. Adding to the problem is the fact that the entire alternator output circulates through the right side of the fusebox (in one 10 gauge white wire and out the other). With all this current running through poor connections…you get the picture. The two 10 gauge spades that connect the box to the car harness can also oxidize. Mine actually went “poooofff” and sprayed smoke as they melted the wiring one day. Remember, that’s the alternator feed. So if your fuses can burn your fingertips, replacing the box is the solution. A cheaper fix is to take out the box, and use a hot solder gun to resolder all the rivets and wire crimps. It only partially worked for me, so I went a step further and soldered a single bare wire across the wires where they entered the “crimps”. NOTE: only solder a wire down the passenger side of the box, doing one on the driver side too defeats the fuses!
This seemed to work much better. All cool now.
VERY POOR IDLE BUT REVS FINE (280Z, overlooked problem) I saw this problem on several when I was autocrossing, including mine. The bellows between the throttle body and the air box develops holes deep within the “folds”. This leaking air screws up the mixture after it’s metered by the air box, but on heavier throttle is insignificant. The bellows may have to be removed to see the cracks, seal them with black silicone. The rubber is 20 years old after all.
STEERING WHEEL VIBRATES EVEN WITH BALANCED TIRES BEFORE GETTING UPSET, DO THESE FIRST IN ORDER OF IMPORTANCE „h tighten wheel bearings „h replace steering rack bushings with urethane „h replace TC bushings with urethane „h replace tie rods „h check for free play in the spider joints in the steering column „h get the front end realigned „h new shocks After having a bad shudder above 70 mph, I found that my left urethane rack bushing was loose! I tightened it and it’s now rock solid at 90! DUMB, this took me a year to find. And if you’ve never tightened your wheel bearings before, it’s time. Remember that steel wheels are notorious for being out of round/balance. And note that few tires are completely round either, due to normal “high-spots” in the belts or tread. Even if in perfect balance, a tire with a high-spot will slightly “hop” on every revolution as it hits the road. This a very overlooked balance problem that affects many tires. I also suspect that the front end is simply resonating due to age and the unibody design. So resign yourself to the fact that you may never get all the shake out.