My New 720 Diesel

[dhp123166]

So my Z finally died and will not be resurrected, after indeterminate time and money and after 16 years of ownership, it's being parted out.

 

So I still like Datsuns and need a vehicle which is mine and built for work, and was fortunate to run across a 1980 720 King Cab Diesel.

 

100 K miles, no smog test needed in this state, and runs like a champ.

 

 

[poor-mans-720]

Oh man that thing looks great... what are the plans for it? anything crazy?

looks super straight and clean...

[hitch]

That powerplant looks completely different from my 81.

[moparvwfreak]

is that a totally stock setup? i didn't think we got the LD20s here. if so i want one!!!!!

 

oh and BTW, nice truck!

[datzenmike]

That's not the stock diesel engine, also the hood is an '81.

 

 

I'd like to see the engine tag.

[wayno]

Does a LD20 diesel use a L block head?

Could that diesel intake be used for an EFI?

This truck has a lot of differant years in it, bumper and marker lights are 83+, hood is 81/82, it's tagged as a 1980, it looks to have an early L16 exhaust manifold, that's why I am asking if it uses a L head.

This must be my truck, who else would do this? <_< :hmm: :huh: :) :D :lol: :lol: :lol:

[poopypants720]

.... so your in California and dont have to smog this truck???? why? cause its a diesel engine?

 

Mines an '81 and has to be smogged... just the same as anything after '75 in california...

[Dead91silvia]

Cool truck! Thats the same color mine was originally...

 

It does have a lot of miss matched parts, thats for sure. The markers, hood, front bumper, but that just might be from having a front end getting crunched... My truck is an 80 720, with a box from an 84, grill/bumper from an 85 4x4, tailgate from an 83, dash from an 81, cluster from an 84, and so on and so on...

 

I really want to know more about the motor! Do you guys is CA really have to do smog back to the 70's?! Thats retarded if thats true! We only go back to 1987 (25 years)...

[DREWSDIME]

Yes here in Cali only 75 and before no smog and diesel are smog exept also, and everytime you purchase a used vehicle (unless its 2008 and up) has to be smogged.

[dhp123166]

Been a while and I am really starting to respect this truck.

 

Working the bugs out...replaced front wheel bearings, front shocks, entire cooling system (removed thermostat, I was told diesels like warmth, but this is SoCal, it's always warm!) all tires.

 

Powerplant is a beast. Two weeks ago did 900 miles in 20 hours straight...no prob.

 

As far as I can tell this vehicle is a marriage between an 80 gas (VIN # indicates this) and an 82-84 720 but I am not sure where exactly the motor came from.

 

The only hiccup has been the water pump. It finally failed, and after examination it looked like the water pump from my dead 280z is a spot on fit...until I removed the 720 water pump. It has this weird one piece design which includes the pulley and the OEM fan and fan clutch. It can be repaired by pressing the old bearings out and replacing but I don't know how to do it and no one around here wants to do it as well.

 

First I tried finding a replacement, the local Nissan dealer basically laughed at me, auto chain stores couldn't really help so it was back to the school of Datsun fabrication;

 

Chopped up the old water pump, pulley and fan clutch combo, rescued the pulley and drilled holes in it so it would line up on the 280z water pump, and had a 1/2" spacer machined so the pulley would line up with the other pulleys. Fits together and runs as it should.

 

Oh and old torqued off water pump bolts that stuck in the block but I have many strange and old screws that sub for these just fine.

 

Then since I did not have a stock fan on hand I shoehorned in a Flex-a-lite slimline fan leftover from my 280z and this does the job of the OEM fan. I thought of eliminating the fan altogether as I do not have a thermostat and the water temp. gauge barely pegs. Over the Route 5 grapevine it rises to just below what stock operating temp. would be!

 

After testing I decided on installing a fan as it keeps the operating temp from changing too rapidly.

 

I like this Datsun because this is a vehicle that serves me not vice versa (like my 280z was)

[HRH]

Not that I'm doubting you, but where are the feed lines for the injectors?

[dayid]

Removing the thermostat is a bad idea. The cooling loop normally works in a whole/partial loop to keep the vehicle cool. When you remove the thermostat, it *always* works in the whole loop. What the thermostat does - is when the vehicle is too cool - restricts the coolant to only a partial loop - letting it warm up more (think of it as warming up/cycling 1 gallon of liquid vs 2)

 

If you believe that "diesels like it warm" yet at the same time your temp gauge isn't riding right in the middle - then removing the thermostat is going to be worse for your engine - since it may remain too cool by not being able to warm up the fluid enough.

 

This is a common problem for folks (like me even...) who had thermostats fail - they normally fail in the open position. When they do this, the coolant is always doing the whole loop rather than properly warming up in the partial loop before reaching the proper temperature (or load) where they need the full loop to keep warm. Normally having a really low temp when not under a load is the sign of a failing thermostat that's stuck open.

 

Your motor running cool is good - to extents - but running too cool is bad. There's a good reason why these vehicles have a thermostat. It's your own - but I'd highly suggest keeping a thermostat. For the $2 they cost it's worth having your motor's temp in the sweet spot.

[dhp123166]

Well the thing is in my experience, when my thermostats fail they always seem to fail closed and this leads to catastrophic failure in other parts of the cooling system; blown out water pump gaskets, exploded radiators etc..

 

Also it seems to happen when I use generic thermostats; LESSON; in this case genuine Nissan is mandatory

 

Diesel engines may like it "warm" (which may be subjective based on geography) but I am pretty sure that cooling systems do not.

 

When I had the thermostat in and went south over the grapevine (an extensive climb from 500 to 4000 ft. over a couple mile distance) the temp. almost spiked to the "H" section".

 

Got home and the decrepit radiator (which was due to be replaced anyway) sprung many leaks.

 

I have found my truck likes nice and level travel whereas hill climbing causes the temp.needle to rise when compared to a gasoline engine.

 

I think it is probably worth it to favor the fragile cooling system than the more stout engine.

 

Still, it's probably worth the phone call to the local diesel shop to get their opinion.

[dayid]

Well the thing is in my experience, when my thermostats fail they always seem to fail closed and this leads to catastrophic failure in other parts of the cooling system; blown out water pump gaskets, exploded radiators etc..

Odd, I've never seen a thermostat fail any way but open

Diesel engines may like it "warm" (which may be subjective based on geography) but I am pretty sure that cooling systems do not.

To extents, they do. Otherwise, there'd be no reason to have a thermostat on any vehicle at all - you'd just run a ton of coolant and have really long lines and large radiators on everything to keep really cool. Engines running too cool can be detrimental to their efficiency and longevity - Not that you use it - but you'll also notice your heater doesn't really work, since it won't warm up enough to get hot air to you.

 

Having a thermostat in and having your temperature almost spike doesn't mean much unless you removed it and found that it was stuck closed - finding a bad radiator afterwards points to your cause.

[datzenmike]

That's because you probably spent more than $2 on one. (I can't see why anyone would cheap put on something so important) Spend the money on a good one (expect $10-$12) and get the type that fail in the open position.

[dhp123166]

Dayid, it was a new thermostat....

 

Well I did call a diesel mechanic and he stated that while he does not recommend removing the thermostat...it will not harm my engine...unless it is under load (which it will never be other than some moderate hill climbing with adequate preparation/ cool down time before) and the temp. rise is uncontrollable.

 

Supposedly it may make a difference in MPG but I have not noticed a difference in the two operating states, I get about 35 mpg with or without a thermostat.

 

If this were a '12 Duromax I would be inclined to run as stated in the vehicle manual, but as it is a 30 year old Datsun, I am inclined to experiment (within reason) just like I did on my 280z (note to self; and see where that got you!!!)

 

So if anyone has an opinion I would love to hear it ; to thermo or not to thermo that is the question!

[wayno]

I like running thermostats in my diesels, it is a measurement that tells me how the engine is running, like a oil pressure gauge, which I also have on my daily driver 1969 datsun 521 diesel with a 1985 SD25 diesel engine, if the temp is low, there is also something wrong, as well if it is high.

I went up the grape vine each way in dec. of 2011, my engine ran a little warm both ways, but that was likely because I was keeping my speed up by flooring it, I think I was down to 55mph at one point both ways, keep in mind that I was loaded with datsun parts also, I suppose if it had gotten any hotter, I would have pulled my foot out of it, and settled for 40mph.

I am using a 1971 datsun 521 1600cc gasser radiator that is in good condition, and it works fine for my 2500cc diesel engine, I want to know whats going on all the time, if it isn't in the middle, it has my attention. :hmm:

[dhp123166]

Now I have bigger fish to fry, going to need a head gasket, starting to see black specks and tendrils of oil floating in the coolant