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Quick Diesel Help (81' 720 SD22)


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So I picked up a nice 81' 720 Diesel last week. Everything seemed kosher, drove her around town for several days with no issues. Today I need to drive to Eugene for a job (400+ miles) and fighting my way through traffic she dies on me. I get her off the freeway and check everything out, plenty of oil, fuel, coolant... however I notice that the top radiator hose is very hot and the lower is not even warm. As for my temp gauge, someone had tried to steal the truck and the wiring is screwy... thus I don't trust the temp gauge being as most of the dash gauges don't work or are wrong. I wait a bit and then pull the radiator cap and start her up, runs smooth. However I don't see the normal turbulence in the radiator with the cap off that signals coolant cycling. I squeeze both hoses and coolant raises... both heater hoses are nice and hot. Main pulley tension is great and turning alt & water pump. I have never seen a water pump go so bad that it doesn't even push a little water through but that doesn't mean it isn't possible! I REALLY need to get to work and would love to get there in my 720 but short of ripping the entire coolant system apart I'm stumped. Any diesel guru's feel like saving my ass?

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Water doesn't always move steady all the time, sometimes it starts and stops till it is warmed up.

You need to get your gauges fixed, overheating diesel engines is bad, and running out of fuel is a pain in the ass also, sometimes getting it started again is a major pain.

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Update: pulled thermostat and now both hoses are hot and water seems to circulate properly however continuing south I got to Olympia and it started loosing power and she cut out on me again... It is about 90' out and I need to fix my gauges and give this beast a whole checkup but getting to work is paramount (and will pay for all the fixes for this beauty) I pulled over to check all fluids again. Everything looked good... I'm not going to push her hard but at this rate I'm going to get to Eugene in about a week! on side note, the previous owner had been running biodiesel in her about half the time he said. I have now put a full tank of good ol' dinosaur diesel in her could this affect anything?

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Check the file filter, sometimes bio and regular don't mix well and cause a sludge like substance that can plug shit up. Also get yourself some power service diesel additive, its better for a diesel made before 2003, it adds lubricity to the fuel that isn't in the new low sulfer stuff, better for the pump

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Every Nissan diesel engine I have ever had that had a home made bio-diesel put through it did not run right anymore.

It sounds like you have a plugged fuel filter, there is only the main one on the 1981, but sometimes smart folks will add a prefilter, this pre-filter is in the engine compartment before the lift pump on the 1982, but some will add this filter back by the fuel tank where the Z24 engine filter is, you need to find out if you have a pre-filter, if you don't then you likely need the main filter changed, and that is something I would not do on the road unless you have done it before.

Where are you at now?

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Did you help him Andrew, good for you, lot of good Datsun folks up and down Interstate 5.  :thumbup:

You guys helped him out alot,, i just made it less stressful by offering to get him to parts store that would even carry a filter (as he wasn't familiar with area) a garage and WIFI to run more questions by you guys,, if it was something more serious ,, or broke.

But you guys called it and off he went.

  I don't think the engine was that hot as you could touch exhaust way up by head,, not sure if that is the most scientific way to do it but it works on the air cooled diesel tractors we use... But it was blazing hot out so taking thermostat out to be safe is a good idea.

 

i felt it was my doodie to give a hand ,, .  We're all in this together 

 

 

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