Exciting 720

[jagman]

Mike I used your list to check out the possible problem(s) and the only thing I find is a scale build up in the radiator.  It doesn't block the tubes but does limit the flow.  I put about a half of a container of CLR int the radiator today and will run it that way for a day or two and then check the scale again.  The only radiator shop here is a butcher and botcher so getting it cleaned or rodded is out of the question..  I will let you know how I make out.

[datzenmike]

CLR is safe for copper pipes (obviously soldered so ok on solder too) I did mine with the rad out. I don't think it will hurt rubber hoses. I also ran full strength and added water to fill rad. My water only comes 7-8 miles from a mountain lake so soft as can be with no dissolved minerals so my rad was pretty good to begin with.  .

[jagman]

Mike I have been using CLR to clean the radiator and it seems to be eliminating the white deposits around the tubes.  When I ran the truck at idle after filling the radiator I couldn't see any disturbance of liquid at the cap opening.  Could I have a bad water pump?  How would I check?

If the answer is yes, do you have a recommended replacement?  Rockauto has a beck/arnley pump that has a decent warranty.

[datzenmike]

The engine would have to be near overheating for the thermostat to be open enough to see much flow. You wouldn't see much flow at idle either. I wouldn't worry about it. 

[jagman]

Mike,  The truck runs hot to the point of boiling.  With no load it consistently runs with the guage at the top of the thermometer sign on the guage or 3/4 up from cold.  With a load it boils.

[datzenmike]

This is a big one...

 

Spin the fan blades by hand. They should turn smoothly but feel like they are in thick honey. When released the blades should stop immediately. If you can get them to keep spinning at all then some of the silicon clutch fluid has probably leaked out. It's intended that at high speeds the effort to turn the blades exceeds  the resistance of the fluid coupling and there is slippage. Thus fan speeds are limited to 1,600 RPM which is more than enough for highway driving and there is some fuel savings and noise reduction. There is a bi metallic 'thermostat' that senses over warmed rad air and increases the coupling allowing the fan speed to increase to 2,100 RPMs.

 

If the clutch fan is slipping excessively it will over heat.

[jagman]

OK They spin and they stop as you describe.  I run the truck at 2500 to 3000 rpm normally ( 50 to 60 MPH ) and the temp creeps up until it hits boiling. I have replaced the rad cap thinking that after 228000 miles it might be tired but that didn't change the creep.

[datzenmike]

Did you try using an infra red gun and shooting the thermostat housing to see what the real temperature is?

 

Have you replaced the thermostat? (too lazy to go back through all the replies)

[jagman]

Yes Mike I put a new thermostat in when I did the head the second time.  I don't have an infrared gun.

Edited September 12, 2020 by jagman

[datzenmike]

Was it over heating back then or did it start after the new thermostat. New does not guarantee it's working. Do you have the old one?

 

The IR guns are $15-$20 or rent/borrow.

[jagman]

Mike I don't know whether it was overheating when I got the truck. I drove it for one day and the small hose under the intake blew and I overheated it.  I pulled the engine and had it bored and the head redone.  When  reassembled everything and finally got the timing correct I drove it once and the lower rad hose became disconnected from the radiator and it overheated again.

I then resurfaced the head using a glass plate and sandpaper as you suggested. The only things on the engine not new is the water pump and the distributor.  I have noticed that while the temp guage goes up as I drive under power  when I coast down long hills it doesn't go down as I would expect it to.  I am at the point where I can only blame the water pump.  I will get an infrared temp guage tho. 

[bottomwatcher]

I have had the cheap thermos bad out of the box that's why I suggested the $15 dollar ones. Was it cheap and country of origin? The good ones have a dual spring set up. Autozone actually has a good one but it needs to ordered usually. The house brand are hit or miss.

[jagman]

The one I bought came from Advance Auto. I have no idea where made.  I will check Rockauto and Lynchburg Nissan for another one.

I just bought a thermostat from nissan and a new pump from Rockauto. I will see if they make any difference.

I figure I might as well spend the money now before all the west coast folks try to salvage the " project truck only slightly scorched"  "suffered only minor fire damage" and parts become more difficult to source.

Edited September 12, 2020 by jagman

[KELMO]

Nissan used to have some T-stat kits that came with gaskets. I think I have some out in the shop. Hold on I'll be right back (hope I didn't pack them away).

 

21200-F3190 76.5C/170 F still shows available through Nissan. Lynchburg shows 3 in stock

21200-P7990 88.0 C / 190 F shows NLA through Nissan and no dealers show stock.

21200-P7991 82.0 c/ 180 F shows NLA through Nissan. Hilltop Nissan in NJ shows 4. 973-887-5400.

 

These kits come with gaskets for L, NAPS-Z, A, E, and CA type engines (Not sure what the CA type is).

Price range looks to be $22.00 to $26.00.

 

EDIT: CA....CA16, CA18

Edited September 12, 2020 by KELMO

[datzenmike]

Change the thermostat first and save the water pump. Water pumps don't stop pumping, they usually leak out the weeping hole on the underside or the bearing goes bad and they get noisy.

[bottomwatcher]

Yep I agree with thermostat first but as far as the waterpump if you have one in your hand throw it on there. I have changed waterpumps in my shop and I have changed them in highway rest stops. I much prefer the shop. It seems 70k miles is good after that it's a gamble. Someone will jump on and say they got 150k on theirs. The life of the pump also depends on proper coolant. I have driven long trips and if it starts weeping it seems to go 200 miles from weeping to gushing.

[Charlie69]

These water pumps have the clutch fans and I have had more problems with the clutch fans than water pumps.  But that could be from the desert heat here in the Phoenix area.

Edited September 12, 2020 by Charlie69

[jagman]

The CLR treatment seems to be slowing the temp rise and for the first time I have seen the temp drop on a long downhill coast. I will add some more CLR to the rad and keep driving the truck until the new thermostat and water pump arrive. 

[datzenmike]

If the clutch fan is firm it won't be the pump. There's literally nothing that can go wrong with the pump itself. Change the thermostat first and try it.

[jagman]

Just curious.  I was at Walmart and a fat lady went past the truck and wiped the green verdigris off the side of the truck bed and it has an ST at an angle in the back.  What does that mean?

I have since wiped the truck down so it looks more blue than green.

[datzenmike]

The ST was an option loaded.... option. Usually electric windows, gauge package, sun roof, variable delay wipers. tach and clock, alloy rims. Most of the options in a single package.

[jagman]

Mike,  I got all but the electric windows on the truck.

[datzenmike]

A side note. You cannot put electric windows in a non electric window door. You would have to swap the doors..... if you were thinking of doing this.

[jagman]

No Mike, I like the manual windows.  I had to special order manual windows in my Dodge.  Just fewer things to fail but at my age they go up and down more slowly along with other things 🙂

[datzenmike]

They have a pill for when you can't wind your window up you know.