Z is Overheating

[Massimo]

I dont know what is causing the Z to overheat. The radiator is brand new and it has a new thermostat. It is a late 74 260z all stock. any help would be great.

[d240zx2]

Did you "burp" it?

Frank

[Massimo]

Did you "burp" it?

Frank

What do you mean by that?

[240ZX]

Was the engine flushed?

Tom

[d240zx2]

Sometimes, when filling a drained cooling system, an air pocket is formed at the highest point in the cooling system, which is the t-stat housing. You've got to clear that air pocket in order for the coolant to flow and cool properly, thus the term "burp."

Some folks choose to heartily squeeze the upper radiator hose to create a bit of slosh that works the bubble out after a few squeezes. Others choose to release the hose clamp at the t-stat housing, pull the hose back just enough to let the air escape, reposition, and tighten the clamp. I like the second method as you are sure the pocket is gone.

Hope this helps!

Frank

[SteveJ]

What is the condition of the water pump & the belt that turns it?

[bobc]

I think we could help you more if you provided a little more info:

1. Why was the radiator replaced?

2. Was it overheating before the radiator was replaced?

3. Have you checked the timing?

4. Have you checked the idle mixture?

5. When does it overheat? At idle? Under heavy load? Just cruising?

6. Condition of lower radiator hose? Does it collapse under load?

Since you replaced the radiator and thermostat it sounds like maybe you were having this problem prior to the work? If so:

7. Has it been using any water? That is have you had to add water to the radiator often to keep it filled?

I think if you answer these it will help us point you in a more specific direction.

Good luck

Best,

Bob

[Massimo]

What is the condition of the water pump & the belt that turns it?

the water pump is new back in the spring the belt is decent but probably needs replaced next year.

[Massimo]

I think we could help you more if you provided a little more info:

1. Why was the radiator replaced?

2. Was it overheating before the radiator was replaced?

3. Have you checked the timing?

4. Have you checked the idle mixture?

5. When does it overheat? At idle? Under heavy load? Just cruising?

6. Condition of lower radiator hose? Does it collapse under load?

Since you replaced the radiator and thermostat it sounds like maybe you were having this problem prior to the work? If so:

7. Has it been using any water? That is have you had to add water to the radiator often to keep it filled?

I think if you answer these it will help us point you in a more specific direction.

Good luck

Best,

Bob

1 radiator was replaced because the water pump shaft broke causing the fan to go into the radiator.

2 it wasn't over heating before the radiator was replaced

3 timing has not been checked since i have had it (4 years)

4 idle mixture has not been check

5 it started to overheat today and i was just cruising it was about 84 today

6 lower radiator hose doesn't collapse under load and is in good condition

7 yes it is using water i have had to refill it a couple of times lately

replaced the thermostat because it was overheating

Thank You for all the help

Josh

[EScanlon]

Having to refill the radiator "a couple of times" says you have a serious leak. Check the engine front, hoses and block for signs of where it's coming out.

The thermostat may not necessarily be the reason for the overheating. I've been told that sometimes NOT having one can cause the engine to over heat due to not allowing the coolant to remain in the radiator long enough to shed heat.

FWIW

E

[sblake01]

..........7 yes it is using water i have had to refill it a couple of times lately

replaced the thermostat because it was overheating..........

Using water? If you don't see it leaking then you've got an internal problem. I once had a water pump shaft break on a 79 510 and it caused a small hole in the timing cover that allowed just enough coolant to seep into the engine and cause it to overheat but not enough to be really noticeable until it got worse. At that point, I thought I'd blown a head gasket until I removed the water pump and saw the damage behind it on the timing cover.

[Massimo]

Using water? If you don't see it leaking then you've got an internal problem. I once had a water pump shaft break on a 79 510 and it caused a small hole in the timing cover that allowed just enough coolant to seep into the engine and cause it to overheat but not enough to be really noticeable until it got worse. At that point, I thought I'd blown a head gasket until I removed the water pump and saw the damage behind it on the timing cover.

Im not sure if this has to due with the cooling system but since you said it may be internal there is some type of fluid that is coming out of the little k&n filter on the valve cover. i think it is a mixture of water and oil but im not sure. the head gasket does not seem to be blown but i dont know all the ways to check, i did check the oil and it is not milky at all.

Josh