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02/25/2006 Archived Entry: "The Datsun Project Report #3 (Tires, brakes, air filter, and coolant)"


Blogispondent Ian here, checking in from the garage with another report on my new (old) Datsun pickup. I've finally been able to start doing some work on it, and I've gotten most of the top priority fixes done. Most of it went smoothly, but I did make one dumb mistake that I can hopefully keep anyone else from duplicating...


The tires that the previous owner had left on the truck were actually trailer-only tires, not rated for vehicle use. And furthermore, they were worn down pretty badly. So, I needed to replace them. I wanted a tire that would be good both on-road and off. The majority of my driving in this truck will be on roads and highways, but I want to be able to hit the trails if I want or need to.

I chose National brand (manufactured by Cooper) Commando A/Ts based on their cost, warranty, and dual on/off road performance. They cost 40% less than the big-name competitors like BF Goodrich, while still getting my mechanic's recommendation and having a 50,000 mile warranty. The design I chose is a compromise, "do it all" tire, offering fairly quiet highway travel, good tread life, and still acceptable traction off-road.

When mounting the new tires, the mechanic noted that all four of the truck's (steel) wheels were slightly bent in places. Not badly enough to be a problem (they each balanced with about 3oz of weights), but he said that had aluminum wheels been subjected to the same abuse they would likely be unusable at this point. Steel will bend, but aluminum tends to crack instead.


While mounting the new tires, the mechanic checked out my brakes (I've had brakes fail on me before, and have no desire to mess with them myself without professional supervision). This truck has disc brakes in front and drum brakes in the rear, and they all checked out well; plenty of life left in both sets. The brake fluid, however, is pretty dirty and ought to be flushed out and replaced. I have not yet decided if I want to do that myself or hire a shop. I don't consider it an urgent issue, though.

Air filter

When I got it, the truck had no air filter at all. Normal air filters are disposable paper deals that get replaced every six months or so. For this truck, I got a K&N reusable filter. This filter offers better air flow than the standard type (and thus slightly better performance), and ore importantly can be washed out and reused for pretty much the life of the vehicle.

Installing the air filter was about as simple as anything can be. The air filter sits in a metal housing right on top of the engine, and all I had to do was open the housing and plunk the filter in place.


Now to the first bit of real work I did myself. When I got it, the truck didn't have any coolant in it at all; the previous owner had left the truck sitting for two years and had drained the coolant. To drive it back to my mechanic's shop I filled it up with plain water. Water will function fine as a coolant, but it freezes, which makes it imperative that you not leave it in an engine when the temperature is below freezing. As anyone who's ever frozen a water bottle knows, water expands when it freezes, and will happily crack an engine block wide open if left in the cold. I knew that, so when I got the truck to the shop I took out the plug in the radiator to drain it. What I didn't realize was that you need to let the engine run while draining it in a situation like this, so that the water pump will cycle all the water out of the engine block. Just draining the radiator will leave water in the engine.

I was very lucky that despite temperatures well below freezing at night, I had no damage to the engine. However, the water in the water pump did freeze. The water pump is a simple assembly driven by a belt from the engine, and so when the mechanic and I started the truck up this morning (to pull it into a bay for tire changing) that belt tried to turn the frozen pump. The pump wouldn't budge, so the belt made a horrendous screeching noise and started slipping across the pump pulley, creating a nice big cloud of black smoke and quickly burning through the belt altogether. Whoops.

The new belt was pretty cheap, and actually was fairly quick to install after the water pump had thawed out. The 22Z engine in the truck has three belts, and this broken one was in the middle. To replace it, I had to remove the fan shroud and the front belt to gain access to the middle belt. To remove and replace belts in any engine, you should find that one of the pulleys is on a moveable mount allowing you to adjust the tension in the belt. To remove a belt, just adjust that pulley until the belt is loose enough to pull off. In my case, the top belt has a pulley on a sliding mount and the middle belt is adjusted by moving the alternator, which has a pivoting mount. Proper tension on a belt is achieved when the belt can be streched up and down between a quarter inch and a half inch in between pulleys (if you're a novice like me, I would suggest finding a mechanic to check your tension the first few times).

After putting the new belt in, I needed to refill the cooling system with antifreeze. I purchased premixed solution, and filled the radiator through the cap located on top. Once it was full, I started the engine and let it warm up, topping off the radiator level as it dropped (when the engine get to its operating temperature, the thermostat will open, allowing coolant to circulate through the entire system, and pulling fluid out of the radiator). I then filled the coolant reservoir to the proper level (having previously washed the old coolant residue out of it).

Lastly, I drove the truck around for a few minutes to ensure that the cooling system was working properly. Since it didn't overheat at all, I consider the work to have been successful.

Next steps

While driving around to test the cooling, I noticed that the throttle was acting sticky, staying revved up after I had let off the gas pedal. There are a couple things that could be causing this, and I will be going through them next. I also still need to change out the fuel filter(s) and differential fluids, fix the broken fan shroud, and replace the damaged battery connections.

Project cost

Here's my cost tally so far for the Project. If some of the parts prices seem low, it's because the shop I'm working in has an account with the local car parts shop, and I'm getting things at dealer pricing.

Datsun 720 pickup: $1000.00
Four 215/75R15 National Commando A/T tires: 339.65
Tire mounting and balancing: $50.00
Road hazard warranty on tires: $39.80
K&N air filter: $43.07
Fan belt: $7.80
Two gallons premix antifreeze/coolant: $14.20

TOTAL: $1498.92

Posted by Ian @ 10:36 AM CST

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