1985 Nissan 300ZX Car is overheating

RICHARDB09

MEMBER
1985 NISSAN 300ZX
236,000 MILES

All of a sudden my car over heats from cold start up to over heating within 2 blocks of driving.
All hoses look good, no water in oil.
Also at the same time this started to happen all my warning lights are on (gas, rear lights front lights, water, oil etc.) When they shouldn't be.

Is there some sort of electrical problem that is causing the car to over heat?
Is this an easy fix?

6 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

As far as the over heating, check to see if the thermostat is working. Also, make sure the cooling fans are coming on when they need to. As far as the lights, that is odd that they all came on. If the check engine light is on, have the computer scanned to identify trouble codes that will help identify the problem. Also, make sure you didn't break a belt. That could cause the lights to come on and the engine to overheat.

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Thursday, June 27th, 2013 AT 5:49 PM

RICHARDB09

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3 POSTS

Thanks,
It looks like I will be taking it into my local repair shop on Monday.

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Friday, June 28th, 2013 AT 4:42 PM

JACOBANDNICKOLAS

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109,885 POSTS

Before taking it to the shop, try checking the things I mentioned. I can help if you get in trouble. Also, our DYI page on the homepage has directions for checking thermostats and other things. Make sure the belt didn't break too. That would cause multiple lights to come on and cause it to overheat.

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Friday, June 28th, 2013 AT 7:53 PM

RICHARDB09

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3 POSTS

I checked the belts and everything looks alright. No broken belts
Do you think everything is pointing to the thermostat?
I don't know how to read the codes on the Nissan, how can I tell if it is the thermostat?
How hard is it to replace a thermostat---- doing it oneself?

Thanks

Richard

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Monday, July 1st, 2013 AT 10:28 AM

JACOBANDNICKOLAS

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109,885 POSTS

Richard:
To properly check the thermostat, it needs to be removed and placed in boiling water to see if it opens. If you refer to our homepage under the DIY section, there are directions.

As far as replacement, it is a matter of draining the coolant below the thermostat level and removing the thermostat housing. The worst part about it is access to what you need to work on. Everything these days are tight to work on.

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Tuesday, July 2nd, 2013 AT 8:13 PM

Z-MODIFIER

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1 POST

The 1985 300ZX has bit of an odd-looking thermostat --- basically, it is a double valve thermostat. As it opens the path for coolant from the radiator it closes down (restricts) that coming from the bypass hose. This is accomplished by moving a restrictor into the bypass channel's path. On normal start-up, this path is unrestricted and allows coolant to mainly recirculate through the block, thus warming the engine up very quickly. Once warm, the thermostat opens up in the usual manner, but also inserts a restriction in the bypass' path. If you have an aftermarket thermostat (one that looks just like an ordinary unit), it will allow too much hot coolant to circulate through the block. Fluid flow is a funny thing. Sometimes it flows one way through a housing, and for no apparent reason, will start flowing in a different manner. Attached is a photo of the 300zx thermostat.

Image (Click to make bigger)