1972 521 Impulse Marketplace Purchase

[EBW]

Hello all.  This is one of those times where Marketplace got the better of me.  I purchased this 72 as a retirement gift for myself and paid more than I probably should have.  Long story short I was hoping this would be a cool project where I could drive it while fixing it up.  But after getting it home I saw more and more issues with it than just the visible ones.  I knew rust would be an issue but im not sure how big a can of worms ill be opening as I start on this.  Hopefully, with the help of this forum, I can get this 521 back to a reliable daily driver status.  My goal is to cruise it around town and the occasional longer distance car events that are a hour or 2 away from me. 

First issue is the throttle pedal that attaches to the firewall.  The bracket is loose ( has a bolt through the middle ) and allows the throttle pedal to move side to side and get caught under the E brake bracket causing the throttle to stay wide open.  That will be my first fix.  2nd is the motor.  When I purchased it, I did a really quick down and dirty tuneup with the carb and plugs/wires/ rotor/cap/fuel filter etc.  It runs ok after a decent warm up, but isnt smooth.  And it seems the motor was overheating. I changed the thermostat and it was puking out coolant.  Has a newer aluminum radiator. Does the inner coolant pasages in the block ever clog or need flushed ? 

Either way, the motor is the next item ill be working on after throttle pedal. I did pick up a backup L16 in case this one is not up to par.  Ideally I would like a L20 and 5 speed, but that is another goal for the future. 

Come along in my journey and hopefully I can get this ol gal back to her glory self.

 

Without furthermore, here she is. 

 

[EBW]

Here are photos of the throttle pedal and how it can get stuck locked under the E brake.

 

Also the pedal bracket and the bolt that is attached in the middle.  Is that stock?  Because the bracket wiggles back and forth along the firewall.  Last photo is the firewall with the washer and bolt as well as the hairline crack.  

[Rotarded]

Mine had a similar "fix" done to it. Its due to the firewall cracking from years of using the throttle pedal. I ended up plating mine cause I am not ready to paint. The proper fix is to weld up the fire wall and fix the mount. The original bracket I believe was tack welded to the firewall. Chances are when they remounted it they adjusted it maybe to their liking or they just poorly chose a hole and mounted it and the result is it rubbing the bracket above. 

[banzai510(hainz)]

dude this is a EZ fix.

the clip I belive goes ove rhte ball of the cable if I remeber right I go to to look at mine.

lower or cut the cut out that end of the pedal is hitting. I just notice it.. Maybe just bent it to the side so it clears. Looking at it closer maybe the spot weld broke and he ran a bolt thru there and it just shifted and hit that causing the shaft to get stuck. Loosen the bolt move the throttle bracket and arm and maybe that will fix it.

 

Datsun are simple rigs but alot of people fuck them upt that think they are car guys. Most are not. 

 

take photos of the motor ect and we can walk you thru this. Be honest most times you dont need to buy tune up kits. Its when peopile install them they fuck it up.

If orginal carb it could be on its last legs. But all this is EZ to fix if one has some basic tool skills. However if one is NOT mechanically or elelctrical inclined they should not buy a rig like this. My 521 dont make it 6months before soemthing goes wrong. Most times it just worn out parts or shit quality parts they sell now as the made in Japan stuff is harder to get. I had alot of fuse box issues and fuses poping . either dirty or bad volt regs or alot of corrossion on the wires which will cause a fuse to over heat and pop. So dont go cutting and by passing stuff liek alot of Morons do. Its a simple wire cleaning in 99% of the time. Reseating connector tighten them ect...

 

wonder how muck you pay for it. To me a 521 not not worth more that 3K but this is a COOL nice rig I LOVE IT AS IS yank the canopy but really it period correct also.. I would not even worry about the rust just drive it.

Fond some local Datsun guys and they can help you thru this. the best improvement I ever made was getting a Electronic ignition. I got a Pertronix conversion but one has to find a single pint distributor and maybe get a couple of them. The when the stock carb went bad I got a Weber DGV 5A manual choke carb.

 

dont be changing shit to just change them either . If you go the orginal coil in there keep it till you know the new one is a correct ohm match. I seento many kids fuck it up with a shiny ne one only to burn the point up down the road then get towed home.

 

you got a nice rig. I wish I had it. But really I would never buy another 521 again. A 510 wagon would be a better choice. But I bet you get the thumbs up driving this.

 

 

so this will give you a idea of whats ahead. If the thing runs good just leave it. swapping a a 5speed is more than I want to do myself as it hard to get up in there ect. carrier bearing crap ect..... a L16 revs better anyway. cause of the shorter stroke. the 521 has suck a low gear ratio. the L20 would be reviing..

 

 

start collecting part. front wheel hubs with the bearing. The Kingpin assemblies upper and lower

brake / clutch master slave clyinders  find the made in japan wheel cylinders and have them on hand as spares. Nabco or Tokico. they will go out. the taiwan stiff dont last and I hate doing a brake bleed . if I just ordered the better part.  My 510 has the Jap made stuff and I never worked on thet car in like 10years. but the 521 it hard. Find spare heater hoses if possible the S shaped one and the longer one. The S shape one is hard to get. Look up Ebay ect.

 

 

also just to kt you know the motor is metric like a 510 but early daysiun trucks are SAE size and threads. so dont go to later datsun and think the bolts swap. the brake are all SAE sizes. then thread. a brake thread for a later datsun 620 is NOT the same.

Edited July 3 by banzai510(hainz)

[banzai510(hainz)]

OH PS I would leave the tires and wheels as is It looks the best with stock hubcaps and white walls like you got them

[datzenmike]

Overheating?

 

Is, or was the coolant colored? green or yellow, meaning did the OP mix antifreeze in? Antifreeze is essential for reducing/preventing rust in the cooling system. If it was orange... that's rust. Flush all that crap out. Pull both the heater hoses off the head and block, set heater to HOT and use a garden hose to flush sediment out of the heater core. Change ends and reverse flush several times. Remove thermostat and lower radiator hose at the engine not the radiator. Too easy to snap the radiator outlet off pulling the hose loose. Let the cooling contents drain out and push hose back on. Fill the block through the thermostat housing and repeat the draining several times till the water runs clear. Do the same with the radiator till it runs clear. 

 

Look in the radiator cap at the vertical cooling tubes. Are they clear and open? or crusty. Crusty would be caused by years of dissolved minerals in the radiator top up water. Never use tap water only distilled in the cooling system and top ups. If crusty looking, pull the radiator out and lay face down with radiator cap on. Fill with CLR to dissolve the calcium and lime. Over night is fine but longer is better. 

 

Buy a couple of gallons of distilled water and a good quality anti-freeze and mix at 50/50 or you can buy it pre-mixed. Use a good quality 180F thermostat and set heater to HOT so the heater fill up. The thermostat is the highest point in the cooling system so air will naturally rise and collect there. When the thermostat opens any air will escape into the top radiator tank and the level will drop. Check and top up to 1/2" below the outlet on the radiator. 

 

 

Over heating is usually one of two things. Not enough water flow to transfer heat to the air or not enough air through the radiator.

 

Not enough heat transfer...

 

1/  Radiator is clogged with mineral deposits.

2/ Really rev the engine while looking at lower radiator hose. If it's gone soft pump suction will cause it to collapse. Hose look ok on the outside but rot on the inside, give it a good squeeze.

3/  Heater leaks, so previous owner by passed the heater by joined the two heater hoses but did not block coolant flow. The very hot water from the head is being sent right back into the engine by passing the heater or radiator.  

4/ Water pump fan belt is not tight or is glazed and slipping.

 

 

Not enough air...

1/  Air through grill blocked by bush bar and off road lamps, license plate or even a spare tire mounted on the front. 

2/  Radiator exterior fins plugged with mud/dirt, bugs.

3/  Fan is damaged.

4/ radiator fan shroud was taken off and never put back on. The shroud increases the fan efficiency. 

 

 

Also ran...

1/  Timing retarded, dumping huge amounts of heat into the exhaust ports, transferring heat into the cooling system.

2/  Brakes dragging.

3/  Head gasket is blown or blowing. Compression can enter the cooling system, pressurizing it past the 13 PSI radiator cap limit expelling coolant and running the coolant low. Symptoms are constant topping up of the radiator, over heating. A compression test may show two adjacent cylinders lower that the other two. These two spark plugs may appear much cleaner than the other two also.

 

In a pinch, if over heating, turn the heater to HOT and run the fan on HI.

[banzai510(hainz)]

If this is a new radiator a aluminum one I hardly think its rotton already.

 

As for the peadal hitting.

i would just rotate the pedal arm till it clears then Clean that lower area where near the bolt is that lower edge and JB weld it and  wait a day for a cure. It might beack loose again  but youll figure a better fix later

 

the lever cap

https://www.rockauto.com/en/catalog/nissan,1971,521+pickup,1.6l+l4,1212321,cooling+system,radiator+cap,2068

[banzai510(hainz)]

the pedal rotating ? run a sheet metal screw in there or a small bolt at the 6 oclock position and  keep it from rotating

or JB weld like I said

[EBW]

Thanks for all the replies and DMs. I am finally able to pull it into the garage and start figuring it out.  My first priority is pulling the carb ( already did tonight) and do a full teardown / clean / rebuild. 

Next is to look at the firewall and make a game plan to fabricate a support and fix the stress crack. Im also looking at the interior throttle pedal bracket and seeing what I can do to fully lock it in.  Goal is to keep pedal arm from wandering and getting "stuck" where it keeps the pedal pegged open.  This was the issue I dealt with when I test drove it.

 

Lastly. Get the engine coolant drained and run the motor flushing it all out.  Hoping to find chunks or crud that would cause the motor to run hot and flushed out. 

 

Here are some photos of the L16 and interior.

[EBW]

Got more done today.  The carb is done minus a couple parts im waiting to get shipped. 

 

I then started on the accelerator pedal bracket issue.  Pulled interior and was surprised how dry the floor was. I was expecting rot in many places.  So that is a win in my book.  The bracket was barely hanging on by just the one bolt. Makes sense why the firewall was stress cracking.  So now to fix this problem.  What have others done in this situation?  Im looking at fixing the crack portion.  Then adding a reinforced piece made of 16 guage that will be welded to the firewall side. Then go back and plug weld the accelerator bracket to the inside.

 

Did the bracket have 2 holes for bolts ? Or was it spot welded ?

 

 

[EBW]

While I was taking out the heater box from the interior, I disconnected the hoses engine side.  

Is this the normal setup for the bend ?  Or did someone make this work with what they had on hand ?

 

Is there a hose that will make the S bend and connect all in one section?

[NC85ST]

That heater hose is definitely not the factory setup. You might be able to take that hose to auto parts store and see if they’ll let you look through there selection of hoses and try to match something up.

[Rustbin]

21 hours ago, EBW said:

Did the bracket have 2 holes for bolts ? Or was it spot welded ?

 

It looks like the factory spot welded it, If you can, plug weld the bolt holes, a reinforcement plate will help to stop it from flexing and cracking again. I made a Z shaped pipe from 1/2" copper fittings on my 510 because the factory hose leaked and I just had straight heater hose on hand, it worked fine but if you don't like the cobbled up look take @NC85ST's advise.

[banzai510(hainz)]

On 7/18/2026 at 9:42 PM, EBW said:

Is this the normal setup for the bend ?  Or did someone make this work with what they had on hand ?

the S shaped hose might have a crack and he repair it doing what he did which isnt a bad fix as the S shaped hose is No Longer Avail as I know .Mine cracked there also from all the motor pulls/head pulls over the years and weakens them.  thats why I dont touch them anymore unless i have too. I hav e a spare set(hoses) and keeping 

[wayno]

I had my gas pedal welded back on my firewall of my 1971 Datsun 521 work truck, it was a challenge as there was not a lot of room, the welder also said the firewall had a galvanized coating on it that made things harder to deal with, I guess you do not want to breathe the fumes, bad for you.

 

Since then, I started using the 720 gas pedal in my 521 trucks, the plate is larger, I do not recall the specifics now, I positioned the pedal to use the stock accelerator cable hole, I do not recall if I bolted it in or did something else, I would have to look and my truck is too far away in the parking lot right now.

[EBW]

I know this is a long shot, but does anyone make a replacement boot? This is the one on the firewall for the E brake cable to go through. 

 

Are there any places to order new gaskets for the 521s ?  

[datzenmike]

With a little work probably a 3D one could be made.

 

Engine gaskets? J13 or L16 engine? Any auto supply like NAPA, Rock Auto, Summit etc. should be able to order them. 

[EBW]

1 hour ago, datzenmike said:

 

 

Engine gaskets? J13 or L16 engine? 

My fault,  I should have said grommets.  Not gaskets.  The rubber grommets that are on these trucks.   I was curious if there are any companies making reproduction pieces.

[datzenmike]

There's really no market for them I would think. 

 

What part? I can look up if it was used on another (newer) Nissan/Datsun.  It's what owning an old classic is all about. You may have to make something or make something work in it's place.

[Rustbin]

2 hours ago, EBW said:

I know this is a long shot, but does anyone make a replacement boot? This is the one on the firewall for the E brake cable to go through. 

 

 

I pull boots and grommets from other vehicles and use what fits, if you have a wrecking yard around visiting it might be fruitful. Autopart stores may have some generic pieces to chose from.

[EBW]

On 7/20/2026 at 7:43 PM, datzenmike said:

 

 

What part? I can look up if it was used on another (newer) Nissan/Datsun.  

I understand working on old vehicles. I guess im just surprised finding out  Datsuns don't have the same support for replacement parts like other older vehicles.   Makes you appreciate more what you have I guess.

 

I was hoping to replace or upgrade the rubber grommets that are in the firewall since these are falling apart.  If none are available, is there anyone on here that is doing 3D printing that sells their items ??

 

[EBW]

Been working on fixing the stress cracks in the firewall. Made an additional reinforcement bracket out of 16 guage.  The accelerator bracket now feels solid and should last for years.

 

The last bit of parts for the carb arrived today as well. Now im switching my attention to getting the engine running efficiently. 

 

[Rustbin]

Datsunparts.com has a cable grommet that looks like the one for your speedo cable. Just thought I'd mention it cause I'm looking for stuff too.

[EBW]

Off to an upholstery place to see what they can do.

 

[Rustbin]

Despite it's ugliness that seat wouldn't be hard for an experienced upholsterer to redo. I would see about putting about a 6" plain panel in the center, seat and back, to break up the length of vertical lines. All the foam can be replaced with sheet stock.