# over heating



## fokis02 (Feb 24, 2005)

I have a problem of an 84 300zx over heating. I have put a new water pump on it and thermostat. Just put an elec. fan on it and it will over heat on the highway. I have flushed the system numbers of times. I'm just lost on where to start now or if I've done all. If anyone has any info please help....


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## asleepz (Feb 24, 2004)

Radiator core might be permantly clogged. How big is the fan and CFM


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## fokis02 (Feb 24, 2005)

fan is a 12in cfm I don't remember at the monment. what should it be you think for a non turbo


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## e_tothe_j (Mar 23, 2005)

hey man i have the exact problem and im still trying to figure out whats wrong with it and ive worked on it for about a month


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## asleepz (Feb 24, 2004)

Fan is a bit small. The stock fan is 16"


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## fokis02 (Feb 24, 2005)

sorry the fan is a 14". Is this a large enough.


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## asleepz (Feb 24, 2004)

It all depends on the CFM.. You can have a 30" fan but if it's only puttin out 500CFM your screwed. 

Did this problem start once you put the fan on and took the stock one off?


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## Zen31ZR (Mar 24, 2004)

To my knowledge, the only correct and adequate electric fan for the Z31 applications is sold by The Specialty Shop and it is 2800 cfm. Anything less will not be enough.


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## fokis02 (Feb 24, 2005)

no it started before the fan...


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## asleepz (Feb 24, 2004)

I believe changing out your radiator core would be the ticket. Seems there's not much else to go wrong.


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## Spongerider (Nov 18, 2002)

Also make sure you bleed the system correctly.


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## asleepz (Feb 24, 2004)

Yes air in the system could also do it.


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## fokis02 (Feb 24, 2005)

I'm changing out the upper and lower rad. hoses. The lower I can squeeze it closed so I think that might be part of the reason. They said that it might close under a load and it only over heats on the highway not around town.
Hope this will do it. The cfm on the fan is 1300. If this don't work I'm going to get a rad. or have a shop reman the one I have.


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## Ant-dat (Apr 20, 2005)

when u flushed out the system was the water brown?
the reason i ask is i had the same problem and found that the rad core was blocked in sections and the rad was only flowing about 50% if that.
When i flushed the system it ahd good flow and was clean, but after running the engine i a little while the brown water was back and i could not work out why,
My car also has twin cooling fans which at the time i bridged and to make them run all the time and it didn't help.

might be worth flushing system again if you had brown water and see if it's brown again, if it is i would be trying a different rad

hope that helps


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## fokis02 (Feb 24, 2005)

no, the water was never brown. before I flushed it when I got the 300, it was green. then I did a new water pump and flushed it then. Everything was great for about 2months or more. then one day going down the highway it started to overheat. So I flushed it so much that the water was clear. then put more ant-frez in to bring it up to the right temp. and that helped but it just still started to overheat on the hwy.


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## Ant-dat (Apr 20, 2005)

u sure it's not a faulty sender? 

I take it't not using water? and there is know signs of head gasket problem?
ie white smoke from tail pipe or oil going tan color


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## fokis02 (Feb 24, 2005)

no white smoke. I have the mix of water and anti-frez just right.


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## Ant-dat (Apr 20, 2005)

oil still black?

just trying to give u some idea's mate
hope u don;t mind?


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## fokis02 (Feb 24, 2005)

oil is ok, but the lower rad. hose keeps vacuuming shut. when it is getting hot or under a load. any ideas PLEASE help. If I can't get it I'm just going to take it to a dealer.


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## e_tothe_j (Mar 23, 2005)

hey man with me having the same problem my advise is to first compression test the radiator and the engine and then get a new radiator its not that expensive and it really cant hurt anything


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## Zen31ZR (Mar 24, 2004)

fokis02 said:


> oil is ok, but the lower rad. hose keeps vacuuming shut. when it is getting hot or under a load. any ideas PLEASE help. If I can't get it I'm just going to take it to a dealer.


Radiator core is blocked or the thermostat is stuck. The hose is collapsing because the water pump is pulling it shut and there is no flow through the radiator.


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## Ant-dat (Apr 20, 2005)

yep sounds like your raidiator is blocked


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## e_tothe_j (Mar 23, 2005)

hey change your radiator I swear thats the problem I was having the same problem as you are and even though I flushed it numerous times and it ran clear as soon as I changed the radiator the problem was fixed so change the radiator and most likely it will fix your problem


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## pearlz (May 10, 2005)

*Running Hot*

I just dealt with a similar problem. My solution was to replace my radiator with a double row core, new hoses and thermostat install an electric fan.

Finis problem!


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## pearlz (May 10, 2005)

*overheating*

My z28 had an overheating problem that resulted in no warning lights going on and the temp guage didn't max out but over time my exhaust manifold warped to the point of busting the front and rear manifold studs and an exhaust leak.

Here's what I did:
1. Got an unwarped exhaust manifold from the junkyard and had it resurfaced by a machine shop.

2. Replaced All water hoses, not just the top and bottom radiator hoses.

3. Removed and rodded out radiator - it was not totally blocked, but blocked enuf to reduce cooling efficiency, and yup, the coolant was nice and green and not brown when it came out.

4. Intalled a new water pump and a new fan clutch.

Remember, the most efficient coolant is plain water, not glycol/antifreeze. Glycol is really not "coolant" it just inhibits freezing. 

Glycol actually reduces the efficiency of a radiator on a hot day. If you want you can go to plain water, but add a can of rust inhibitor from the auto parts store. If you live where it freezes in the winter just remember to go back to "coolant" in the winter months.


pearlz


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## JAMESZ (Mar 12, 2004)

Try getting a new radiator cap. My dad's Jimmy would overheat and one of the hose's would keep closing up; it was the radiator cap replacing it fixed it.


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## fokis02 (Feb 24, 2005)

Had to get a new Rad. just got it in and it works fine thanks for the input. But now I have other problems. Will post the new problem.


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## Zen31ZR (Mar 24, 2004)

Glad to hear you got teh one problem fixed, at least.....


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