240z overheating at idle in traffic lights and intersections

[jalexquijano]

Okay, finally decided to pick up my1972 240z from the mechanic. Charged me US$160 for changing the fan clutch, thermostat, wrapping heat shield cloth on the fuel lines and replacing wáter pump. He also changed the exhaust manifold pipe gasket. Car timing was set at 10BTDC. Car ran fine. No backfire either from intake or exhaust. However, once i reached home while playing with the car stereo temperature started to rise until reached 3/4. RPM dropped from 1000 to 500 and then raised to 1000 again. A few seconds later it stalled and i had to crank it again. It does the same at intersections and while at idle on traffic lights. Took out all plugs and cleaned them. I guess i will need to take the radiator out and flush it completely. The problem clearly has to do with heat. What a waste of money and time.

Any opinions on how to solve this or should i just hang the towel and hire an expert from this fórum to come to Panama and fix my car??? What is the going hourly rate?? The car has the stock carb heat metal shield also installed. Am i also missing another part?

[Jarvo2]

Might want to think about rebuilding your engine then.  Check out all of the 40+ year old gunk that I found inside the water passages of my '72 240z as well as the clogged PCV filter screen inside the engine block.

[siteunseen]

1 hour ago, Jarvo2 said:

Might want to think about rebuilding your engine then.  Check out all of the 40+ year old gunk that I found inside the water passages of my '72 240z as well as the clogged PCV filter screen inside the engine block.

Same here. Can't trust 40 somethings or forty year old cars.

I used picks and screw divers even a Dremel to remove the hardened sediment at the rear of the block between 6 & 5. And that's when I got it back from the machinist!

 

[jalexquijano]

the person i bought this car supposedly had the engine overhauled by Datsun LLC with the following description:

Vehicle Insight

• PerTronix Ignition Kit with new coil
  Electric fuel pump 
• Recent rebuilt Engine
  Recent rebuilt 5 speed transmission from 280Z with new Center Force 1 clutch with stainless steel clutch hose
  New Twice Pipes Exhaust
  60-Amp Alternator upgrade kit
  New fuse box
  New Fan belt with new upper and lower Radiator hoses
  New 3 row Aluminum Race Radiator
  New Plug Wires
  New Thermostat and oil pressure sender
  New brake system with stainless steel brake lines
  New struts
  Rebuild Carbs

Driver's Insight

The current owner of this classic 1972 240Z has authorized us to put it up for sale. He has owned the car since 1997; the car has been garaged the past 15 years. The car has had a complete mechanical refresh and is ready for final restoration. The engine and transmission have less than 6000 miles on them. The following is a list of upgrades or modifications made to the car:
New Datsun L24 motor has crank and rods from a L26, special oversized 84mm flat top black coated pistons from D.L. Potter Engineering with E88 Head and Far 311 New Race Cam

Could Datsun LLC have missed getting the gunk out of the car? How much will it cost me to accomplish this cleaning? Ive already spent US$6,000 in parts and labor and still have the rough idle, stalling and overheating problems since day one!! I could have bought 3 engines with all the money spent!!

[Mark Maras]

 It seems like it's cooling problem is caused by a lack of circulation, a lack of volume and or a lack of heat transfer to the coolant. You've replaced the fan clutch (hopefully it has a lot of resistance) so presumably the fan is pulling enough air at idle to cool and a new water pump to make sure circulation is good. Crud build-up in the block and radiator not only reduce coolant volume but also interfere with heat transfer from the heat source to the coolant be it liquid or air. The heat transfer is increased greatly if the circulating coolant is touching metal. Crud buildup acts as an insulating layer. Cured the problem in mine with two GOOD flushes and sent the rad. out to be re-cored with additional layers to increase the volume. That made it much better. Temp would still rise under extreme conditions. When I eventually replaced the clutch fan (it seized) with a flex fan the engine never overheated again. Although I've not tried it, I think one could pull the manifolds and remove the expansion (freeze) plugs and clean out the block without removing the engine.

Tips; If you're stuck in traffic not moving, shut the engine off. Mine always started easily so I wasn't concerned with blocking traffic. It won't create more heat if it's not firing. If you're moving slow, keep the RPMs as low as possible. If it is overheating, increase the heater control to hot and turn the blower on high. Better for me to overheat than the engine.

[siteunseen]

Datsun Parts LLC, missing something? That's the joke of the day, congratulations. 

[jalexquijano]

Mark,

Thanks for the advice. The car does run nice at 10BTDC even though it has a Schneider 274F Cam which i was recommended to set to 12BTDC. I dont think the difference will help the engine run cooler. I have an AC installed so no heater control or Factory blower to depend on.

How much shall i pay for a machinist to clean the crud build up and what kit or parts shall i order if he will need to carry out this task. Will i need to purchase a Brand new Champion 4 row radiator also?

[psdenno]

A search on this site, and other Datsun Z sites, for "Datsun Parts LLC" and "California Datsun" will bring up earlier message threads that will offer insight into what may be the reason for the engine problems you're experiencing.  Shady engine rebuilding history with many complaints of unwillingness to stand behind completed work.  

Dennis

Edited December 31, 2015 by psdenno

[jalexquijano]

I even e-mailed Datsun LLC regarding the history of this engine and they replied telling me they dont store information of the rebuilt engines. Anyway, if i am gonna remove the engine for cleaning the crud and sediment build up in the wáter passages, i  need to know what gaskets will i need to purchase to do this properly. Anyone???

Edited December 31, 2015 by jalexquijano

[siteunseen]

I would buy, or borrow, an infrared thermometer and check the temperature all over the motor while it's idling.  $50 at amazon.com

Did you install an electric fan?  Seems like that video guy said that was the most helpful thing he did.

[siteunseen]

Or a cheap meat thermometer in the coolant. You need some numbers before you go through all that trouble.

[Stanley]

I have the same radiator, runs cool even in very hot conditions. There are engine flush chemicals at any auto parts store, and many auto mechanics will do a flush where they circulate chemicals through the engine for several hours. cost about $50 to $75.

Did you try the test I suggested (start engine with radiator cap off, and let it idle until the thermostat opens. You should be able to see a vigorous flow of water) ? If so what was the result?

There's another test for blocked radiator. When the engine is warm and thermostat open, place your hand on various parts of the radiator core to feel for a cool spot.

Did you replace thermostat with genuine Nissan? Nissan parts man suggested 180F thermostat.