chaseincats

ok, I'll grab that. 2 quarts should fill a '78, right?

Hi guys, Going to change my transmission fluid today but can't find a definitive answer on what spec GL-4 fluid to use (75w-90 for example). Does anyone have a definitive answer? -chase

You really should check the engine for vacuum leaks. I found mine and it completely changed how the engine ran and only took 10 minutes to find/seal all the leaks. Here's how you're going to do it: - head to harbor freight and buy a hand "transfer" pump like this one: https://www.harborfreight.com/Multi-Use-Transfer-Pump-63144.html - get a rag and plug your air intake (otherwise the smoke will leak out here) - unplug your brake booster and plug the "out" side of the pump's hose in there - grab a pack of cigarettes from 711, light one and put its end into the "in" side of the pump and start pumping. After 2-3 cigarettes your engine should be full and you will see smoke start to sneak out. Cap/fix those leaks. NOTE: You must do this when your engine is cold and this is done with the engine off. I'd also check and make sure you are getting spark to all cylinders. Pull all the spark wires and stick a screwdriver (with a plastic or wood handle) into where the wire connects to the plug and then hold the metal of the screwdriver a centimeter or two above some body metal and crank the car. If you have spark to that plug you will see it arc to the car. The video sounds like the car possibly isnt running on all cylinders. If that is indeed the problem, don't stop there - seal your vacuum leaks too via the above method.

Agreed - MSA and especially James have awesome customer service

Hi guys, I found a battery hold-down bracket and J-hook in my box of parts but cannot find the bolt needed to secure it to the firewall. Does anyone know the size/pitch of this bolt and I'll head to Home Depot tomorrow? All I am able to find is the nissan part number which is 08360-61812 and the bolt is an M6 but I can't find the pitch anywhere... This is the bolt area I'm talking about:

TBH I didn't know there was supposed to be a gasket there either. The gasket seems to be NLA though...

For the record, you don't need a spare spark plug to test spark. Just unplug the center lead on the distributor cap and hold the metal spark plug connector next to the body metal. No need to find/buy a spark plug to test.

I didn't open it but there was no fluid in/around the brake booster also that master cylinder is less than a year old so it should be good

Update: The source of the vacuum leak (where the engine rpm would rise when the brake pedal was pressed) was the ends of the brake booster/check valve vacuum hoses. They were old/flayed so I snipped the ends off and put new hose clamps on em - worked like a charm. Thanks for your help, everyone!

It won't fully deplete the booster's vacuum if the pedal is held. The gauge will drop about 5lb of vacuum on pedal-in and 5lb on pedal-out regardless of how long I hold the pedal down. The interesting bit is there is a hiss sound on pedal-in/pedal-out if the vacuum gauge is below 4lbs of vacuum remaining in the booster.

Gotcha, thanks so much for your help. I'm guessing that the small increase in engine rpm when the brake pedal is held is probably coming from the stretched/hardened ends of the brake booster hoses. I clipped the ends and re-installed them. I will test the car in the next few days.

I'm using a hand pump and I've gotten it up to as high as 22lbs before my hand said enough. It's ok its depeleteing a set amount even though vacuum amounts are being detracted on pedal push in & the same when the pedal is returned (the gauge drops pounds on 2 different actions)?

So I just went downstairs to test it and here is what I found: The booster will hold vacuum indefinitely if vacuum pumped and the pedal isnt pushed Vacuum pressure is lost when the pedal is being depressed and when returning to the non-pressed stopper. If vacuum pounds >5lbs, holding the pedal in will only deplete a set amount of vacuum silently If vacuum pounds <5, holding the pedal will cause a hiss until the booster his 0 lbs of vacuum Any ideas on if this is dead or not?

Thanks for both posts' explanations, that makes total sense. So that means that in order for a brake booster to be bad - it would need to not be able to hold a vacuum with the pedal not pressed and me pumping the vacuum gauge pump?

Awesome, glad I don't need a new booster

So I put a vacuum gauge on the booster and pumped it up all the way to 22 lbs without a problem (for at least 10 minutes until I disconnected the line). When I push the pedal, there is a hiss and vacuum pressure drops to zero. Is that how brake boosters are supposed to work (holding vacuum until the pedal is pressed)?

It's a top mounted unit

Hi guys, My brake booster definitely has a small but increasing vacuum leak. I know it's leaking because if i hit the brake pedal the engine rpm slightly rises. I noticed yesterday the brakes really arent what they used to be when going at speed (new pads were put on about 8 months ago and the car has probably been driven fewer than a few thousand miles so that isn't it). Also it wouldn't be the master cylinder as a new one was installed last July. My question is, I'd like to get a larger non-vacuum leaky booster on there and I hear the 79-81 ZX's 10'' booster is the way to go. I can't seem to find a definitive yes or no as to if that will bolt right onto my '78 without needing to modify the piston length or requiring a new master cylinder which which works well currently. Any ideas? -chase

lol what im gonna do is wait until it says empty again (9 gallons remaining) and bend it one direction or the other until it reads 1/3 full now that i know a solution lol

The tank isnt dented so I just think its that I need to bend it and yep, the tabs are lined up.

gotcha, thanks guys, ill straighten the arm then

By that you mean straighten the arm, right?

So when I bend the arm, am I straighening the bend or bending the arm further in the same direction?

Ya, a few other members of my local z club picked up the zcardepot sender units when they first came out a few months ago and all work great - yes its the factory connector, its plug-and-play.

Right - both senders had clean coils (I cleaned the first one and the second one was brand new) and I'm having the same issue in the exact same portion area of the gas gauge. For reference this is the sender I got: https://zcardepot.com/collections/fuel-sending-units/products/copy-of-fuel-tank-gauge-sending-unit-sender-240z-260z-280z-70-78