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Temperature issues... or are they? 
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Joined: Thu Sep 11, 2008 9:15 am
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Car(s): 1965 Wasp, 1966 Bellett, 1967 Bellett, 1969 Florian, 1973 Bellett GTR, 1976 Buick Opel by Isuzu, 1978 Gemini van
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Hi guys,

Well the website has been going for about 3 months (has it only been that long?) and it's about time someone put a question in the HELP! section. Why? Coz I need HELP!

My ratBellett has always ran kinda cool; down the bottom quarter of the gauge, but with recent hot weather and now that I live at the top of the biggest hill in town, it's been getting a bit warm.

So I changed the thermostat, but the car ran 'hot' straight away! I checked the 'stat and replaced it, but it was fine (it was an 82 degree thermostat).

So I trundled it off to a radiator place. They found the cooling system to be about 25% blocked but much to their surprise, the gauge was reading rather hot even after they cleaned it all out.

This Bellett is a 1967-68 model and all of my glovebox manuals are for the earlier model! Dammit!

Anyway, this is where my gauge sits now:

Attachment:
Bellett temperature gauge at 'normal'.JPG
Bellett temperature gauge at 'normal'.JPG [ 96.91 KiB | Viewed 9753 times ]


The radiator shop dudes reckoned that at the bottom of the white block was about 70-ish degrees, while the top of the white block (right under the hot section) was 90 degrees. With the cleaned system and new thermostat, the needle now sits somewhere in the middle of the block - about 82 degrees which is spot-on for the thermostat, but it's a fair way up the gauge and doesn't leave much lee-way if it IS overheating! I mean, if it's at 90 degrees, that's ok, but once it goes over, there's not much warning coz by then it's right in the HOT zone!

Anyway, the old thermostat was a 74 degree item, but it was broken and stuck open so it was just letting water flow straight through more or less and this is why the temperature usually ran so cool.

My guess is that if I put a (working) 74 degree thermostat, it will sit lower on the gauge; probably more around the bottom of the white patch. This will give me more warning should it actually overheat, but it's not real close to 'optimum' operating temperature.

So if anyone can give me some guidance on this one, that would be great. I spoke to PR91 on the phone and he gave me some good advice, but I thought I'd get a 2nd opinion just in case (no offence dude!).

By the way, the temperature has been pretty consistently in the white block either when it's cold or even yesterday when it was about 32 degrees celcius. The only time it went up higher was when I let it idle for ages with the front of the car near my shed door (probably not much cooling there) and when the radiator guys deliberately covered the radiator to get it to warm up a bit as a test.

HELP! Any advice appreciated!

PS I'm going to double check the timing too; I think it needs tinkering.


Oh yeah, and in case this makes a difference, it's actually a 1600cc Florian motor.

Cheers again!


Dave

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Mon Jan 05, 2009 11:54 am
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Joined: Wed Sep 10, 2008 1:22 pm
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Location: Adelaide, Australia
Car(s): 1968 Isuzu Bellett Deluxe (Polynesian Blue), 1974 Datsun 240z, 1970 Datsun Fairlady SRL311, 1966 Prince Skyline
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Hey Dave.

The only thing I can add is that my 1500 engine sits at exactly that spot on the gauge, maybe a little lower but still in the white. On the drive to the nationals last year she would over heat to the bottom of the red block if I sat on much more than 100kph but that was a pretty hot long drive.

As you know I'm running the 82 degree jobbie with no problems and I know my radiator is stuffed so I recon you're not too far off the right spot anyway...

Does it smell 'hot' when you pull up and check the engine? Any burning or leaking coolant?
What did PR91 say? Where is 'normal' on the gauge anyway? So many questions!

Good luck resolving the problem if indeed there is a problem :)

Cheers,
RS

BTW, did you take that photo while you were driving?

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Mon Jan 05, 2009 12:18 pm
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Location: Melbourne, Australia
Car(s): 65 and 66 sedan
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Dave, I would not be putting a great deal of faith in a 40 year old Temp gauge. You can get some really nice looking after market gauges which discretely hang below the dash and give you an extremely accurate reading before every thing go's wrong.

I have always ran a thermatic fan on my Bellett and have always been very pleased with the results. The best part of the thermatic fan is that it will give you the maximum amount of cooling when the engine needs it regaurdless of the engine speed. Another thing that I did when I put my recored radiator in my car was to run an inline filter sock in the top radiator hose. Even though my motor was freshly built and the block had been chemically flushed every time I check the sock, even 8 years down the track there is still a little bit of grit caught in it. Had I not installed the sock all of that grit would be in my radiator.

Another thing to have a look at is your heater core or even the impellor on your water pump as it could be a bit corroded and not giving you optimum flow.

GAv

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Mon Jan 05, 2009 1:47 pm
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What you are observing is the problem with putting the temperature sensor for the dash gauge in the radiator, and not the engine itself.

The sensor is in the exit side of the radiator, so it is telling you the temperature of the coolant after it has passed through the cooling fins, and at its lowest temperature before it goes back into the engine. The thermostat is meant to allow the engine temperature to quickly come up to operating temperature, then open up and send the coolant through the radiator to maintain that temperature. A low temp thermostat in summer weather will open all the way and allow full flow through the radiator until the engine is turned off and the engine cools. In cooler weather, or with a higher temp thermostat, the flow will be slightly varied, restricting flow through the radiator to keep the temperature up. Meanwhile, the gauge on the dash only tells you what the temperature is on the cool side of the radiator. The cooling ability of the radiator is going to be relatively steady, so whatever the inlet temperature is, it will cool X number of degrees.

The dangerous part is when the thermostat fails in the shut position, the gauge never shows any increase in water temperature, and the driver finds out after the head is warped when the car comes to a halt at the side of the road.

If you changed to a different temperature thermostat, then it will be opening and closing at a different temperature, and you should see the needle on the dash at a different position.

With a fuel injected car, you could hook up a scan tool and read the temperature sensor in the engine that the computer uses to determine the actual engine temperature. Short of a test gauge and hooking up a test sensor, that's not an option with a carburated car.

It's summer where you are, so it might be worth the time to remove the thermostat, drive the car, observe the needle position, and take notes. Then, maybe try out the original thermostat, and take notes. And compare with the new thermostat.


Mon Jan 05, 2009 5:07 pm
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Car(s): 1965 Wasp, 1966 Bellett, 1967 Bellett, 1969 Florian, 1973 Bellett GTR, 1976 Buick Opel by Isuzu, 1978 Gemini van
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2ldohc wrote:
Does it smell 'hot' when you pull up and check the engine? Any burning or leaking coolant?
What did PR91 say? Where is 'normal' on the gauge anyway? So many questions!


BTW, did you take that photo while you were driving?



Yes it does smell a bit hot and it runs on, which it didn't do when it was operating at the lower temperature. Having said that, it probably needs the timing adjusted a bit, which probably isn't helping temperatures either.

Yes I was driving. At about 60km/h according to the weird factory-or-aftermarket-metric-cover-that-goes-over-my-imperial-speedo-and-leaves-the-odometer-in-miles!

Cheers for all your help.

I'm a bit disinclined to pull the whole thing apart again, especially when I just paid $500 to have it pulled apart and put back together by professionals. And theoretically I did take notes coz I ran it with the broken-open 74 degree item, the 82 degree item (which caused overheating, but this may have been unnecessary panic coz I wasn't used to the gauge reading that high) and with no 'stat coz I took it out compeletely to drive it to the radiator joint. It sat quite low on that journey, a bit below where it sat with the broken 74 degree item.

I don't think the gauge is at fault (factory-fitted position of the sensor aside) and when those guys had a thermometer in the coolant it stayed in the white zone even with when up to 90 degrees (max).

Bah, I'm going to do the timing and see how it goes!

If anyone has a copy of the manual for this model that shows 'normal', it would be great if you could scan it as a matter of interest.

Cheers again; heaps of responses and I was only gone for a minute (well, overnight, but whatever).

!@!

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Mon Jan 05, 2009 9:02 pm
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Car(s): BellettGT, Wasp, Florian, Piazza, Jackaroo
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Running low temps wears the engine. I have always run the std 82 degree thermostat.
I had a similar problem with my first GT. Ages to warm up (thermostat stuck open) then overheating (corroded impellor).
I always replace all hoses and get the radiator flushed/checked for engine rebuilds.

Anywhere in the white is supposed to be ok though mine rarely run above 1/2 way, though I have run at "just touching" the red line for several thousand km (Florian).

The Bellett temp sender sits at the engine water exit. The sender needs to match the gauge - I think there are 3 or more variants (early ones work backwards in newer gauges).

Since I'e run new waterpumps (with coolant), corrosion isn't a problem nor is hose gunking (restricting flow) so it's usually the radiator's fault if I have overheating problems.

The pumps are well sized - Belletts typically run cooler without the thermostat (some cars with faster pumps overheat instead) but it can be a good test for flow - if it still eventually runs hot it could be impellor problems, gunk or a radiator problem.

Check too that the plumbing is ok. Some cars go crazy if you re-route the heater lines, though Belletts usually do not have this problem.

The timing could be too retarded (runs hotter).
Ensure your oil is topped up (about 40% of engine cooling).


Wed Jan 07, 2009 12:48 pm
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hi dave here i am new but have checked in the68 model i have both books 68 says divisions of th thermometer indicate the cooling water temp between 50degrees to 110degrees celcius or 122to 230 farenheit in normal driving the thermometer pointer indicates within the mid section of the division which corresponds with the temp range between 70 to 85 celcius or 158 to 185 faranheit this all quote page 15 in the early model manual page 20 says about the same adding .......when the indicator is far away from this position ,then check the causes and in the hardbound full workshop manual (lucky arnt i ) itsays the usual things which you know timing ,thermostat,and finally leaks into water jacket hope this helps regards dave


Wed Apr 22, 2009 12:27 pm
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Wow, thanks everyone for throwing up so much info. Dave, there's nothing I can add, and I've 'learnt' a million in the process. Though the temp readings for a calibrated GT gauge read about the same, in fact a surprise to find we run a similar engine models. Yes, when I had true over heating problems some years ago, the radiator joint said it was 90!! pecent blocked @#$. Now changing coolant and flushing every 10,000 k not an issue with a recored radiator, considering thermostat working properly.

Scenario, cool day, engine will get to just below operating temp and stay there for a longtime. The engine will perform a little tighter and not get to loose fanging stage unless you take it for a long hard drive.

A temperate day, 25 to 30 degrees ambient, engine will get to optimum temp and run more relaxed, more open to run a little harder. In fact ideal.

Hot day, will run just above normal, toward the offset middle mark of 120F. Idling in traffic sends it slowly toward 120 ( after all it is a tiny radiator ). Great idea thermo fan, dudes ( but not original ).
Meanwhile, the best remidy I've found is place your big toe onto the 'celerator to 1500 rpm cause the engine lumps more the hotter it gets, and only fan speed will suck enough air through the radiator fins. If the needle on the gauge spikes to beyond the 120 mark its time to park it.

B.


Wed Apr 22, 2009 3:18 pm
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Guys, info I have received is that you can buy a 71 c thermo from the HQ holden and it will fit and does a great job, I am going to try one anyway, the last thing you need in a Bellett is getting too hot, next thing you will be repalcing head gaskets.

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Sat Oct 31, 2009 7:36 pm
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Car(s): 3x1965 PR20(Donkey, Jenny n Bundy) 1 1969 PR20(Percy) 2 1968 PR20(Eugine n GT Donor) 1 1968 PR91 GT, 1 1965 Wasp
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You have to love it when can dig up a post from the past that seems to have the answer to the question you have in mind.
My question is exactly that of Dave's.
I have just put a replacement radiator and new thermostat in Donkey and was a bit disconcerted when the temp needle ran right up to the hot mark before the thermostat seemed to open then it dropped just below the halfway mark, but once all the coolant was at operation temp the needle hovers at 3/4 or just over (as in pics)

I was a bit concerned for the same reasons Dave mentions at the start of this post and my new thermostat is also a 82deg jobbie.
I'm sure I will get use to it but still a bit edgy as it is a new engine and all....

Any opinions to alleviate my anxiety while I thrash the ringer out of my new engine???

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Sun Sep 13, 2015 1:43 am
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Hey there Sticky.
I always run a TT160 (160F) Gemini thermostat rather than the 180F one. That is probably 74C. I prefer the lower temp, no loss of performance, better fuel economy and more leaway on hot days. Guages typically sit just below the middle of the white block on late and Florian guages, right on the mid stroke (normal) on teardrops.
Cheers, Matt.

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Sun Sep 13, 2015 12:04 pm
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Cheers Matt
I don't think I like the 180 I have in there now, it makes me nervous watching the needle dancing around the hot line, so I might get a 160 instead for it.

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Sun Sep 13, 2015 9:58 pm
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Hi Guys
don't take my word as gospel but my understanding is that Unleaded fuel burns hotter and faster than the old leaded.
Lead was added to slow the burn / flame front and lubricate the upper cylinder.
When using unleaded common practice is to retard the timing by about 2' and expect it to run around 82' for maximum efficiency
Common also to run cooler plugs like a BP7EV rather than the BP6EV.......
You can also get high flow versions of the Thermostats so alternately a high flow 82' but as the standard Bellett cap is only 7 PSI they tend to overflow readily.
Newer cars run over 15 PSI pressure systems with overflow bottles
My 2 cents worth
Cheers
J

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Mon Sep 14, 2015 1:14 am
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Asroc66 wrote:
Hi Guys
don't take my word as gospel but my understanding is that Unleaded fuel burns hotter and faster than the old leaded.
Lead was added to slow the burn / flame front and lubricate the upper cylinder.
When using unleaded common practice is to retard the timing by about 2' and expect it to run around 82' for maximum efficiency
Common also to run cooler plugs like a BP7EV rather than the BP6EV.......
You can also get high flow versions of the Thermostats so alternately a high flow 82' but as the standard Bellett cap is only 7 PSI they tend to overflow readily.
Newer cars run over 15 PSI pressure systems with overflow bottles
My 2 cents worth
Cheers
J

Interesting, My Sport runs a 7psi cap and overflow bottle as standard. It uses BP7ES I think plugs. One thing I can't find out is if the later Belletts ran unleaded fuel in Japan back then (1972) Anybody know?

glenn

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Mon Sep 14, 2015 4:28 am
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One would assume they did. In 1970, my boss took on Toyota. I was pricing a valve for a R12 engine and wanted to know why so dear. Was advised that the head of the valve was filled with, I think, sodium. And the stem was made of stellite to accomodate for the unleaded fuel. Also found out in 1975
that the G161z engines were developed for unleaded fuel. I was also advised most of the Japanese manufacturers were developing their engines on unleaded.
When I had my sedan engine overhauled and had G161Z internals fitted I used the 160 degree thermostat. They also fitted new valves from a late model Isuzu engine. Radiator was recorred.
7lb radiator cap with a Rodeo/Faster overflow bottle. Temperature stays at the comfortable level
that I was used to watching.

Dave.

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Tue Sep 15, 2015 11:09 am
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