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260z Overheating issues


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#1 260

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Posted 06 June 2012 - 09:32 PM

Hello Their,
I'm new to the forum,

So I purchased a 1974 260z 2+2 off a fellow member and since I have had it I can't drive more than 15 minutes without it overheating.
so I have tested the thermostat, flushed it, checked fan,checked water pump cleaned it out all new gaskets screws and sealants, clean out rad,
pretty sure not the head gasket.
Noticed oil smelt like it had a small amount of petrol in it, checked hoses were not collapsing, seems to be ok while idling in driveway.
Ordering new aluminum radiator just in case, rich while idling.
would really appreciate some ideas and advice thank you.
Taner

#2 pauly_adams

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Posted 06 June 2012 - 10:58 PM

i would seriously just change your thurmostat, same thing has happened to me twice and both times it was the thurmostat, they appear to work but just dont open all the way what you can do is take it out see if it overheats if not then its your thurmostat.

#3 Daedalus-Z

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Posted 07 June 2012 - 01:59 PM

+1 to Thermostat.
Assume when you say 'overheating' it's the gauge reading high? Check the radiator/hose and make sure it's actually getting hot (water is flowing past the thermostat). It's such a cheap item and so easy to replace you might as well! :)

#4 260

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Posted 08 June 2012 - 12:12 AM

Ok so I ran it without the thermostat still gets really hot, no it actually overheated and pissed out fluid everywhere gauge got to 120 :(

#5 benny

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Posted 08 June 2012 - 12:55 AM

my next guess would be your radiator is full of crap blocking the flow

#6 Linton

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Posted 08 June 2012 - 07:58 AM

if you take out the t/stat water has no restriction so it flows so fast through the radiator it cant cool down therefore boils, put in a new one and try it my guess is h/gasket or even w/pump.. when it is idling with the cap off any bubbles coming up??
Linton

#7 Patch

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Posted 08 June 2012 - 08:18 AM

If you do have bubbles and you loose water, it can be  a cracked head, compression super heats the water .
I would try a bottle of Chemiweld before starting to pull things apart, I managed to get 5 years out of Cressida with a bottle each year. It was pouring water out the exhaust, blowing water out the radiator, and oil in the water and water in the oil, running on a couple of cylinders sick as, 5 min's after treatment runs fine.
My Bob cat has now gone 5 years with one bottle.

#8 Zedman240®

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Posted 08 June 2012 - 11:20 AM

Has the car sat around at all with no water in the system at all? That happened in my case and all the sediments dried up and hardened in the radiator and blocked 3/4 of it.. drive for a bit and it's ok then shoots right up to over heating. I'm with Benny, thoroughly check your radiator...
Also check for a temp difference (with your hand before it gets too hot) between the top and bottom rad hose; if the one near the thermostat is cooler than the lower hose, water is not circulating ie could be either rad or tstat.

#9 Zedman240®

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Posted 08 June 2012 - 11:30 AM

Also this post is in Electrical Systsem and not in engine...

#10 Bozo

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Posted 02 September 2012 - 03:44 PM

Give it back and get a refund.

Let us know who the member you purchased it off is and we'll fix him up :)

#11 Lightmaster240z

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Posted 02 September 2012 - 03:57 PM

Bozo behave young fella ;)

#12 fluegel

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Posted 04 September 2012 - 02:04 PM

Check the ignition timing my volvo 240 was set at 40deg advanced which caused it to get hot enough to blow gaskets. When I ran my Z after replacing the head it also ran hot until I got the timing right.

#13 260Coupe

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Posted 04 September 2012 - 04:40 PM

Another item to check is the water pump...........the pump veins can rust away to nothing and inhibit circulation.

If your radiator is clear, your thermostat is Ok and you water pump good then look for a blown head gasket, easiest way is to pull out the plugs and look for one that is has been steam cleaned.

Also make sure you have flushed your cooling system with a radiort flush to get the gunge and rust out of the water jackets around the block.

my 2c

Al.




#14 sexual_sushi

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Posted 04 September 2012 - 05:28 PM

Looks like that might be my old bus that I sold to another guy on here ;) Different engine to when I had it though.

Is it a 3 core vl or vn or 'whatever bloody crappy car' it comes off radiator? And does it have a 12 inch thermo fan on it? If so it did cool fine with daily driving on the old engine, even in traffic in summer. I think the thermo fan controller might have been fried when I sold it, I assume they fixed this or might have replaced with an original fan setup?

#15 Z.

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Posted 04 September 2012 - 06:09 PM

Yeah definitely agree with the other boys.

Replace that thermostat first      >>  try chemiweld (even a few bottles)    >>      then pull your waterpump and check that

I think most likely waterpump but other 2 are easier to try first ;).. also just make sure to keep an eye out for milky looking coolant, sure sign of problems in the head as it leaks oil into the coolant

Good luck!

#16 Daedalus-Z

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Posted 05 September 2012 - 02:54 PM

Radiator Cap too!
I think we missed that one! Dodgy cap will stop the system from pressurising properly so could cause the coolant to prematurely boil. Plus they are cheap and just about the easiest thing to replace on the whole car (provided it's not actually overheating and spitting boiling liquid at the time).

Correct me if I'm wrong there, that's just what my limited understanding suggests!

#17 Agno

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Posted 16 September 2012 - 07:19 PM

You would be right Daedalus! That would have been the first thing I tried, after that feel the top and bottom rad hoses when the car is warm to check for blockages.

After that I would be looking at the thermostat and then the radiator. In this case start with the cheapest item and finish with the most expensive 8)

#18 stevo_gj

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Posted 16 September 2012 - 11:37 PM

if you take out the t/stat water has no restriction so it flows so fast through the radiator it cant cool down therefore boils,


I've read this statement before on this forum, pretty sure it is incorrect. Increasing fluid velocity increases the convective heat transfer, which will improve the efficiency of the whole system, which results in lower average water temperature.

#19 zeds4ever

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Posted 19 September 2012 - 09:55 PM

??? Two other checks for head gasket problems is oil deposit in radiator cap when removed or also a milky colrd residue in oil cap when removed.Compression test is best method to check thoroughly but best take two readings .First one while motor is cold & the second after the motor has been warmed up to allow metal to expand & problem to be more evident. If both readings are fairly close it's not the gasket.If there is a distinct variation of readings then it is either the gasket or the head is cracked.

                                                          Regards: Alan.  :D       

#20 Patch

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Posted 20 September 2012 - 08:51 AM

A lot of places have these testers that change colour if it detects combustion gases in the radiator, these gases super heat the water, you can have a cracked head and not show water in the oil or oil in the water,
My 306 pug showed this, and a bottle of cemweld fixed it.

http://t1.gstatic.co..._YCxHa3KO1FcBcA




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