Z is Overheating

[ohio260z]

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

[ohio260z]

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

[ohio260z]

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.

[ohio260z]

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.

[ohio260z]

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

[zbane]

. 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.

When my head gasket blew, none of the coolant made its way to the crankcase (or at least not enough to be visible). I had been overheating, and had replaced everything you have, including the radiator at 1 in the morning, in the rain.
Have you checked your compression? That was the final indicator in my case, as well as the car simply refusing to start...

[ohio260z]

When my head gasket blew, none of the coolant made its way to the crankcase (or at least not enough to be visible). I had been overheating, and had replaced everything you have, including the radiator at 1 in the morning, in the rain.
Have you checked your compression? That was the final indicator in my case, as well as the car simply refusing to start...

the car still runs pretty strong but i would guess that doesn't mean that one cylinder has a leak in it. i also discovered that there might be some kind of blockage in the coolant system due to the fact that the coolant doesn't seem to be flowing and then the thermostat opened up causing coolant to overflow out of the top of the radiator.

[zbane]

Since you have discovered an apparent blockage, I might suggest a complete drain (make sure the heater controls are set to hot so that the coolant in there can drain as well). How you do this is up to you, but I purchased a Prestone back flush kit and fit the "T" connector on the right hand side of the block behind the "J" tube between spark plugs 1 and 2. Fairly simple operation, cut out some of the old tubing, install, tighten, and follow directions.
Others may have other ways to do it, but I like the kit since it allows you to top off the radiator from below the upper edge, helping force the air bubbles out.

[zbane]

A photo should explain it a bit better.

[ohio260z]

the only thing that makes it a little weird that i flushed the system back in the spring and i have been driving it since may a couple times a week so it could be a good possibility that the head gasket is blown or i have an internal leak due to the fluid that is coming out of the little k&n filter on the valve cover

[beandip]

If you have water in the oil , get it out of there ASAP and flush the engine with good oil and a new filter. Water in the oil , the oil turns into mayonnaise and is a poor lubricant . Plus if there is oil in the water it will raise hell with the new rad.

[ohio260z]

If you have water in the oil , get it out of there ASAP and flush the engine with good oil and a new filter. Water in the oil , the oil turns into mayonnaise and is a poor lubricant . Plus if there is oil in the water it will raise hell with the new rad.

is there a way to tell if there is oil in the water i have never dealt with a problem like this before if it means i need to do a rebuild then thats what i will do just gives me a reason to start a refresh on the car

[Tarmac]

Drain the oil. If it's milky, it's got water in it. Looking at the dipstick wont really tell you if it's got water in it unless it has a LOT.

[ph240]

If the old water pump broke it could have worn a hole in the timing cover which would explain the "Milky oil" in the crank case filter. As the bearings wear the shaft cam move causing the impellers to cut into the timing cover. You can pressurize the cooling system to about 15 to 20 lbs with a cooling system pressure tester and see if it will hold pressure, if not remove the valve cover, look down at the timing chain where the water pump would be. It sounds like a timing cover or blown head gasket.
This does require your attention as it will lead to more seriuos problems.

[ohio260z]

If the old water pump broke it could have worn a hole in the timing cover which would explain the "Milky oil" in the crank case filter. As the bearings wear the shaft cam move causing the impellers to cut into the timing cover. You can pressurize the cooling system to about 15 to 20 lbs with a cooling system pressure tester and see if it will hold pressure, if not remove the valve cover, look down at the timing chain where the water pump would be. It sounds like a timing cover or blown head gasket.
This does require your attention as it will lead to more seriuos problems.

Thank you everyone for your help! This problem will more than likely not get fixed until this winter because it is not worth fixing when i want to pull the engine and do a rebuild on it. And the transmission needs some work along with a few other things that need some attention. Also the car will not be driven due to the fact of causing more damage.