Run hot suffering

[Datsun fan]

Hi guys, It's the Spartana truck again!

The engine is used A15 A and 3N71B automatic; it is in excellent shape, copmression check

results are 145 Psi for all cylinders, timing is set well and belt is tight .... bla bla bla

the radiator is out of Hyundai 2.4 diesel van copper multi-core 65*35*7 cm with fittings on

the hot side for tranny cooler, T-switch is 75-80 c (and is tested)and mounted in

left-bottom-front area of the rad, the cap does holds pressure and right hose has a spring,

no leakage, bottleneck......... and two rad-mounted electric fans which blow very good air

flow (stock clutch fan has been removed).

The coolant is 4 liters Desert ice ethylene glycol(40%) and added anti rust/corrosion (240 ml) .

T-stat is stock 82 c (and is tested) and installed so that the spring is towards the head!

The head temp sensor is stock (and is tested) and if the temp is 86 c then the dashboard temp

gauge needle will be in the middle . Ambient temp is 32 c .

 

I start the car, it will take about 7 minutes for the coolant-type choke to disengage, then

I drive it in town normally, the temp gauge needle reaches the middle and after one minute

the fans will be activated, after 10 minutes the needle is at 1/3 and the fans will stop for

about one minute and the cycle will continue.......

Driving uphill (500 m long)then the needle will start to go to 2/3 and further(pinging and

loosing some power), so I stop and let it cool for 10 minutes and the fans will stay on for

long, when pour some water on the rad the process will take a little time less .

Driving downtown on slight incline up will cause the fans to stay on for long (35 minutes

and more!) .

Driving on highway, the gauge temp is a little lower and the fans cycle is 15 minutes on and

another 15 mins off .

When idle, the temp will stay at 1/3 and fans cycle is 4 min on then 13 min off .

I tried to use 71 c T-stat but no change .

I tried to flush the engine, rad, heater many times with water, diesel oil and rad flush

fluid and there was a lot of rust and crap .Then I used the mentioned coolant and I still

get some little rust powder and unknown solid black powder from rad cap.

When checking the temps, the bottom rad hose is hot and the upper hose is a little hotter .

Coolant temp at the rad cap is 43 c .

the head is stock and never been shaved, plugs are BPR5 ES .

How to lower operating temp to normal ?

How to reduce fans working periods to minimal?

What is the correct T-stat rating for A15 ?

What is the optimal operating temp for A15 ?

[thisismatt]

What condition is the water pump?!

[KELMO]

Nissan lists an 82CC and an 88C rated thermostat (210) and on a 310 they list as low as 76.5. The models listed are 1980 - 1982.

[Datsun fan]

The water pump is in very good condition . No wiggle, no leak and no whine . the vanes are in very good shape and I tested the pump it throws well :rolleyes:

[]2eDeYe]

I still get some little rust powder and unknown solid black powder from rad cap.

 

Is this after cleaning the cap? Black powder could indicate carbon and a head gasket leak. Are you looosing any coolant?

 

I don't understand why the fans would turn off if the engine is still hot.

[Datsun fan]

Is this after cleaning the cap? Black powder could indicate carbon and a head gasket leak. Are you looosing any coolant?

Yes, This is AFTER cleaning the cap.

No, I'm not loosing any coolant .

Head gasket leak = low compression reading which I already don't have!

Fans turn off = Engine is NOT hot . The idea is when stepping A little hard on gas pedal or when going up hill the temp will easily increase and then the fans will take a long time to stop automatically!

[hang_510]

was the rad checked before installation? (or was it new?)

[hogboy52]

Retarded ignition timing can cause overheating. Is the auto transmission shifting down properly when climbing a hill?

[datzenmike]

Thee fan shouldn't come on if driving above 25-35MPH. There is enough air being pushed through the rad for proper cooling. Low speed or stopped for lights may trigger the fans. Things to try:

 

Replace thermostat... they are so cheap they are not worth testing. If you have a new one this means nothing, it could be bad in the box. Change it.

 

Have the rad flushed by a shop. Open cap and look at vertical cooling tubes ... are they scally ?

[]2eDeYe]

Head gasket leak = low compression reading which I already don't have!

 

Fans turn off = Engine is NOT hot . The idea is when stepping A little hard on gas pedal or when going up hill the temp will easily increase and then the fans will take a long time to stop automatically!

 

Your head gasket can leak without a loss of compression. It is rare, but it can happen. Also some coolant leaking into your cylinders can actually increase your compression in some cases.

 

Not sure I understand the second statement there. Language is a funny thing :)

 

You could have a rust blocked passage in the cooling system as well. Have you have the system flushed completely? Is this a new motor or rebuilt motor?

[hang_510]

2eDeYe' date='01 July 2010 - 12:55 PM' timestamp='1278014148' post='320876']

Your head gasket can leak without a loss of compression.

mine was (over)pressurizing into the radiator, which is how i figured out why it was losing coolant.

comp was even across all 4

[]2eDeYe]

mine was (over)pressurizing into the radiator, which is how i figured out why it was losing coolant.

comp was even across all 4

 

This is what I was getting at with the carbon on the cap. You may not even loose any noticable amount of coolant in the right situation, but your engine will still build up excessive heat.

[zed]

The fact that the motor is overheating at highway speeds indicates that the fault does not lie in the fans. The bottom rad hose should be noticeably cooler than the top - otherwise the rad is not removing heat from the coolant - I would get the rad opened and rodded out by a rad workshop.

[Datsun fan]

was the rad checked before installation? (or was it new?)

No, It was used one .

Retarded ignition timing can cause overheating. Is the auto transmission shifting down properly when climbing a hill?

Ignition timing is set according to manual ,Auto transmission is shifting down properly . Anyway the truck is heavy

and the engine is subjected to heavy duty operation .

Thee fan shouldn't come on if driving above 25-35MPH. There is enough air being pushed through the rad for proper cooling. Low speed or stopped for lights may trigger the fans. Things to try:

 

Replace thermostat... they are so cheap they are not worth testing. If you have a new one this means nothing, it could be bad in the box. Change it.

 

Have the rad flushed by a shop. Open cap and look at vertical cooling tubes ... are they scally ?

I tried TWO brand new (TAMA brand) 82 & 71 c and ONE USED 82 c t-stats (all been tested)and

the same shit happened.

I tried another used water pump with no luck, no change .

The black powder thing I see in coolant is solid like rock, and doesn't dissolve neither in

water nor in organic liquids so it is obviously not a carbon thing. Anyway, after "fishing"

about teaspoon of that thing from rad filling hole it stopped coming out!

Sorry mike I can't take a look inside rad core to see if the cooling tubes are scaly due to

rad design .

mine was (over)pressurizing into the radiator, which is how i figured out why it was losing coolant.

comp was even across all 4

I always perform compression check with radiator cap open and keeping an eye on coolant

level, No coolant coming out from the radiator while cranking and good compression readings

then the head gasket is OK that which is confirmed by the plugs color is perfect and exhaust

emissions analysis (there will be very high hydrocarbon compounds reading if the coolant has

contact with combustion chamber) . Now please just stop considering the damn gasket as the

culprit .The engine is USED one .

I need answers for questions in the first post please.

how to check if the transmission is the overheating part?

[Datsun fan]

The bottom rad hose should be noticeably cooler than the top - otherwise the rad is not removing heat from the coolant

 

Any examples??? Any numbers .

My lower rad hose is about 52 c when engine is warm, Is this normal??

[datzenmike]

Take the rad in and have a shop flush. I don't know what they use but has anyone tried CLR? That would dissolve lime scale. The black shit could just be paint off some internal part.

 

 

Any examples??? Any numbers .

My lower rad hose is about 52 c when engine is warm, Is this normal??

 

I don't think any generalities can be made about lower rad hose temps. All motors are different. All that can be said is the the rad should shed excess heat and the lower hose will/should be cooler.