Overheating problem

[Brett240]

OK, now that ive found the new thread button (thanks for your insightful help Alfadog!) heres my problem.

my engine has always run a little warm butover the last few days my engine has been overheating pretty badly, mostly in traffic.

its got a 3 core radiator, 10 inch thermo fan (which due to my electrical prowess is currently on fulltime) and i replaced the thermstat last night. It still overheated in traffic this morning.

heres the thing, i tested the old thermstat in a pot and it remained closed even when the water was boiling, so i thought this HAS to be the problem, but alas the new thermostat hasnt helped (maybe a little bit). any ideas?

[Zedrally]

Oh I hate writing this, but are you sure you put the thermostat in the right way?

A quick way to check is to leave it out and see if the engine still overheats.

[Brett240]

well thats another story alltogether. it seems nissan in their infinite wisdom have replaced the original design thermostat with an updated version which has a diameter that is too big for the hole! being a little frustrated by this i grinded the outside of the thermostat down on a bench grinder until it fit in the hole. AND as far as i can tell its in as properly as its going to get.

is there a replacement aftermarket thermostat that will fit?

[Zedrally]

Yes, Repco, KMart etc will have one.

There seemed to be a production fault with the ones that fitted on the L series.

They would after a short period of time seize up.

I haven't had much success with any of them and now run both cars less thermos.

It's a bit cooler in winter here in Melbourne but I would think you would have optimum temp in NSW!

[Brett240]

i might give that a try and see what happens, unfortunatly in NSW its still pretty cold in the mornings this time of the year, and a combo of the extra warmup time with no thermostat and my almost non existant exhaust system does wonders for the neighbor to neighbor relationships!

[sjcurtis]

Brett240,

The moving carpark on Sydney roads kills Z engines for a number of reasons. I used to drive Richmond-Mascot and Mascot-Richmond dailly for a while saw some high temps doing that.

With thermostat choices and supply, I now it is hard but shop around. You need a thermostat that will fit straight in "Bulb down", ideally an all stainless steel construction with a bleed by hole in the perimitter land ( this coud have a borbal attached). Look for quality in the build. Also for Sydney traffic go for a low temp value to give you early opening, even the coldest of these will warm quickly and clear screens in the mornings. With you fan system is it restricting flow through the radiator core when you are mobile, effectively not performing to optimum mobile, I still use a clutch fan to minimise this.

Hope this helps

Steve :classic:

[zoom240]

Brett240, by all means do the simple stuff first. But I have to share my overheating problem, which seems to be solved ... finally. Car was overheating in traffic - fine otherwise. Replaced the thermostat first with aftermarket model, no luck. Replaced the radiator cap. No luck - but now the system was finally pressuring up. I began to spring leaks. Had the radiator core cleaned out & leaks fixed. Ended up replacing the heater valve too. Replaced the water pump & fan clutch. No luck. What finally fixed the overheating problem was just buying a new radiator. I think the old one was clogged with crap. The Z's seem almost capable of running air cooled when they're on the highway -- I've driven the car home when it was overheating, with heater blasting away - only to find out there was very little water left in the radiator.

Of course, when all the parts are new, it ought to work ... but what a pain in the arse. Almost sold the car over this. Hope your problem is just a thermostat.

[Brett240]

Thanks for your help guys,

well i pulled out the thermostat last night and took it for a 45 min drive. while moving the car was cooler than it had ever been before, running about half as hot on the temp gauge and the engine felt stronger too.

when i hit traffic up went the gauge again, and on came the heater, which barely could keep it from overheating.

its great on the move though, so i figure it needs more cooling when stationary. im going to try twin thermo fans and im going to flush the whole system out on the weekend and see what happens.

[ZCCOR#109]

My previous experience with overheat on my 72 was due to crap in the radiator core. Having it "boiled" out did the deed.

My overheat was at highway speed however. Above 70mph when the heat being generated was greater and the flow to cool the water was being restricted.

Attention!! New thermostates can be bad. They are cheaply made with poor QC. Also, a system may NOT cool well without a thermo installed. Water can flow TOO fast through the system not gathering enough heat from the engine and not give off sufficient BTU to the airflow, and thus retain too much heat in the engine. Check any thermo that is questioned with an acurate thermometer in hot water. Bring the water temp up gradually and observe the action. Remember the opening is small, and can be difficult to detect.

If you live where anti freeze is not needed try Red Lines water wetter. Racers swear by it reducing operating temps.