240z overheating at idle in traffic lights and intersections

[Zed Head]

On 12/31/2015 at 6:36 AM, jalexquijano said:

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.  I guess i will need to take the radiator out and flush it completely. The problem clearly has to do with heat. 

 

"3/4" is not very hot.  There are numbers on the gauge also if you want to estimate temperature.  But a thermometer in the coolant will tell more.

All that you've described  is that the engine runs better cold than warmed up.  Might still just be running lean.  

Don't get distracted thinking that the engine is overheating until you get some real numbers.

[jalexquijano]

On ‎01‎/‎01‎/‎2016 at 2:49 PM, Zed Head said:

"3/4" is not very hot.  There are numbers on the gauge also if you want to estimate temperature.  But a thermometer in the coolant will tell more.

All that you've described  is that the engine runs better cold than warmed up.  Might still just be running lean.  

Don't get distracted thinking that the engine is overheating until you get some real numbers.

Okay i bought a heat gun and point it directly to the radiator and the thermostat also. When the car is at 3/4 it is Reading 185 degrees Farentheit! Should i consider removing the thermostat and running the car without the thermostat to see if the problem continues. I have not found the invoice of the Champion 3 row radiator. Could any of the rows be damaged also and not letting the coolant and wáter run through the engine properly?  I took the car to a Radiator shop and the owner told me that before i deliver the radiator to him for flushing and fixing, i need to test the car with no thermostat!

Which radiator upgrade would you recommend for this car in the event one of the rows is blocked:

Mishimoto 3 row:

http://www.tdamotorsports.com/index.php?route=product/product&product_id=316

or

Champion 4 row:

http://www.championradiators.com/Datsun-240z-radiator-4-row-1970-1973

Thanks for your great help!!

 

 

 

[Zed Head]

15 minutes ago, jalexquijano said:

Okay i bought a heat gun and point it directly to the radiator and the thermostat also. When the car is at 3/4 it is Reading 185 degrees Farentheit!

That's not very hot.  Most thermostats are 180 degree thermostats.

A better test of if the cooling system can handle the heat load is what the temperature gauge does while driving.  If it climbs to a spot as the engine warms up and sits there whether you're driving hard or just cruising, that's a good sign that the thermostat is opening and closing properly and the radiator is removing heat when it's open.  If the temperature keeps climbing the harder you drive it then drops when you take it easy that's a sign that the radiator can't remove heat faster than the engine can produce it.

If the temperature climbs at stop lights but drops when moving that's a sign that there's not enough air flow over the radiator.  A bad fan or fan clutch, or the need for a fan shroud.

[siteunseen]

That's what the gauge on my red 240 reads, same as yours. Has it ever been noticeably lower in the past?

You could run it without a thermostat. Get another gasket then pop the cover off, no need for the Porsche mechanic.

[siteunseen]

Knowing that's a datsun parts llc motor helps understand the low psi.

[psdenno]

If you look at your temperature gauge, you'll see that the numerical range is from an indicated 120 to 250 degrees.  That means that the center mark on that scale would be, wait for it, 185 degrees.  If your temperature gun reading of 185 on the radiator is an accurate measure of coolant temperature and your dash temperature gauge was accurate, the needle should be at the half way point on the scale, not at 3/4 as you show in the picture.  I would suspect an inaccurate temp sending unit or gauge out of calibration and not worry about the reading on the dash gauge.  Now, on to the stalling issue.

Dennis

[Jarvo2]

Agreed with the rest, gauge reading looks good.  There's also that Water Wetter product that you can put in the radiator to make everything run cooler.  

 

http://www.redlineoil.com/product.aspx?pid=117&pcid=10

[jalexquijano]

13 hours ago, psdenno said:

If you look at your temperature gauge, you'll see that the numerical range is from an indicated 120 to 250 degrees.  That means that the center mark on that scale would be, wait for it, 185 degrees.  If your temperature gun reading of 185 on the radiator is an accurate measure of coolant temperature and your dash temperature gauge was accurate, the needle should be at the half way point on the scale, not at 3/4 as you show in the picture.  I would suspect an inaccurate temp sending unit or gauge out of calibration and not worry about the reading on the dash gauge.  Now, on to the stalling issue.

Dennis

The Rough Idle and stalling issue is attributed to ???????? We have changed almost everything: Fan clutch, wáter pump, pertronix ignition, spark plugs (NGK BP6ES), spark plug Cables (Blue NGK), gaskets, Rough Idle and stalling only happens when car reaches to very hot temperature when at idle and not moving. I even have the MSA Fan Shroud installed.

[psdenno]

1 hour ago, jalexquijano said:

The Rough Idle and stalling issue is attributed to ???????? 

 

I think we can rule out overheating based on the temperature readings you took.  Actual temp is within normal range, gauge reads,high.  So, some questions.

Did the Z ever run well after you bought it?

If so, how long, weeks, months, days?

Did anyone check the running condition of the car for you before you bought it?

if I remember correctly, you're taking the previous owner's word for what was done to the Z mechanically before you bought it.  The engine rebuild was provided by a questionable vendor who has had many complaints about shoddy engine rebuilds in the past.  You won't know what's in the engine unless you tear it down and rebuild it - a costly process.  I'd suggest looking for an experienced Nissan mechanic and start over if you plan to keep the car.

Dennis

[Stanley]

Maybe try temporarily installing a set of points (set dwell per FSM with dwell/tach meter) to rule out a possible problem with the Pertronix.

[jalexquijano]

2 hours ago, psdenno said:

I think we can rule out overheating based on the temperature readings you took.  Actual temp is within normal range, gauge reads,high.  So, some questions.

Did the Z ever run well after you bought it?

If so, how long, weeks, months, days?

Did anyone check the running condition of the car for you before you bought it?

if I remember correctly, you're taking the previous owner's word for what was done to the Z mechanically before you bought it.  The engine rebuild was provided by a questionable vendor who has had many complaints about shoddy engine rebuilds in the past.  You won't know what's in the engine unless you tear it down and rebuild it - a costly process.  I'd suggest looking for an experienced Nissan mechanic and start over if you plan to keep the car.

Dennis

It had a Far 311 Race Cam when i bought it thus causing rough idle and the temperature always inscreased to 3/4 as per the picture attached. I replaced this cam with a Schneider 274F, lashpads, springs, and Nissan OEM Rocker Arms. I also sent both of my SU Carbs to Ztherapy for full rebuilt. How come i am still having this rough idle and stalling issue. Datsun LLC rebuilt the engine and was purchased by PO through EBAY.

[psdenno]

You keep mentioning that the temp increases to 3/4.  THAT IS NORMAL.  Let me say that again, THAT IS NORMAL.  Your car is not overheating.  You measured the temp with the heat gun at 185 degrees.  185 degrees is at the 1/2 hash mark on your gauge.  Your gauge is not accurate and is reading high - no Bueno.  See the red zone on the temp scale near the 250 on your gauge?  If the needle was there, you would have a problem.  

I would be more concerned about low oil pressure since you mentioned that the engine has a new oil pressure sending unit and your gauge reads near ZERO.

Carb adjustment is critical and MAY be the cause of your rough idle and stalling issue.  Clogged fuel filters can also be a reason for what you're experiencing.  Good luck with future troubleshooting.

Dennis