300zx 4-Piston Caliper Upgrade Problem....

[REC]

I recently upgraded the calipers on my 90 Q45 with the 4 piston 300zx calipers. My brakes were working fine before but i wanted the increased performance. A member here named Wes told me that i could use the stock brake lines I just needed to shorten the brake line bolt to fit the caliper. After cutting off the heat shield and shortening the bolt me and a friend began to bleed the brakes and everything went as planned until i started the car. When the car isnt running there is plenty of pressure on the brake petal but as soon as the car is running the pedal is mushy and goes to the floor and doens't get any stiffer after pumping it several times. Obviously when driving around the parking lot there is literally no brakes at all as the pedal goes to the floor. I'm basically stuck and have no idea what the problem is. Has anyone experienced this before with this upgrade?

[Razi]

You might get great responses if you posted in the Q45 section. I hope everything works out fine

[redtop91]

^ He has the 300zx calipers now. MASSIVE NO NO USING THE STOCK LINES ON 300ZX BRAKES!!!!!!!! If you use the stock banjo fitting, even with a shorter bolt, it is not the right fitting for the 300zx caliper. The Z brakes don't have a tab to hold the banjo fitting in place and the fitting will spin and loosen the bolt which is probably what you are experiencing. VERY DANGEROUS! I don't know if you have a Q45 or a 240 since your profile says Q but you posted this in the 240 forum, but the lines on the Q and 240 are similar enough so the same rules apply.

[REC]

I have a q45 but knew this was a common upgrade for 240's.... So which lines should i buy? The fitting is on tight and is not spinning loose. This is happening immediatley after the install. Whats the different about the aftermarket banjo fitting? So basically your saying that i need to get 300zx banjo bolts and run aftermarket lines. The calipers didnt come with any line bolts thats why i modified the q45 ones.

[redtop91]

No no need for the 300z banjo bolts. Just use a set of PDM stainless lines. Other than that I'm not certain for the Q45. Elwesso knows everything about everything Nissan Infiniti, and he has a Q. He'd probably know.

[ca18datsun510]

the first thing he said was that he installed them on his 90 q45.

anyway, i have a feeling its an abs related problem.

and you can also get away with stock 300 lines if they are a close enough length.

[redtop91]

He didn't specify so I assume he was talking about the Q45 lines which are identical to the 240's.

[REC]

He didn't specify so I assume he was talking about the Q45 lines which are identical to the 240's.

Since the pedal gets mushy only when the car is running i too think its involved with the abs. Have any ideas on possibly what?

[yessir240]

What the hell? the 300zx has 4 piston calipers? i thought they were only 2 piston?

[AmoebAssassin]

Sounds like a combination of air in the system and a leaky or underpowered brake booster.

Did you point the bleeders up when you installed the calipers? If not, there might still be air in the calipers.