p.s. I've already read Nick's saga with his head gasket, and I'm hoping that my problem is something else...

I have a day to fix this before I move back to Sydney to start uni...

The enmity I feel for my car at the moment is unparalleled. Here's the problem: I've recently replaced the radiator and fitted a thermofan and overflow tank, which both are working fine to the best of my knowledge. The problem is... on long highway/city runs, the car often overheats - slowly, nothing violent, but enough to necessitate stopping and letting it cool down before proceeding...

I've found that removing the vacuum tube from the advance mechanism on the distributor helps to slow this overheating down, but it still happens...

Perhaps the worst part is that this doesn't always happen. For instance, driving from Sydney to Mittagong today, I had to stop once at Wattle Grove, where I let it cool down, then I had to stop at Mount Annan, where I let it cool down and refitted the vacuum advance tube as an elimination, then again just near the Picton exit, where I let it cool down and removed the vacuum advance tube again, and after all this it finally ran cool enough to get me all the way home, even having the audacity to cool down enough for the thermofan to switch off when I was about 1km from home.

Some things I thought might have been the cause:
1. Ignition system - I doubt this because as much as I try to get the correct ignition timing, it still happens

2. Radiator cap - I doubt this because I replaced it two days ago and it still happened today

3. Thermostat - I'm planning on checking this out after having a very late lunch. If it's stuffed, I will take action, and if there's no bleed hole I'll add one. It's a genuine Nissan one though, and only a year old. It should be okay.

4. Loose tappets - there's been an unnerving noise coming from the rocker cover for at least two years now, which I suspect to be loose tappets but really I have no idea. I will check this out later today or tomorrow, provided the next option wouldn't be more likely...

5. Head gasket - well after reading Nick's saga, I suppose the cause could be a bad head gasket. I would really rather that this wasn't the case, but if there's no other alternative then I suppose I have to.

Please tell me what you think.

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Iain
Datsun Stanza GX
AKA "Stanley", "The Brown Bullet"
5 speed dogleg box, mechanical secondary throttle, Bluebird S2 radiator & fan, off-road spotties, paralysed nodding dog, "invisible dashboard", Volvo cold air duct

What car / motor is it?

Do you have a clutch fan on the radiator, or just the thermofan?

Does the car overheat if you start it and just let it idle for ages?
Does it overheat in normal driving conditions?

Have you got any aftermarket things on it, like a weber carbie, turbo whatever?

If you've blown a head gasket, wouldn't the oil be whitish in colour as it is mixing with the oil?

Anyways, more info needed.

- Nath

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'71 1600, L20B, 45 Weber, Extractors, Elec' Ignition, 200B struts/sumitomo 2 spot brakes, 240k 5 speed, R180.

nath,

Stanza, L16

Thermofan

Does not overheat if just idling, will in fact cool down over time when idling if it's been overheating

Will overheat a little during normal driving (I think so anyhow) but not as much as when on highway

No aftermarket things other than a cool air tube and a 5 speed L series gearbox

No whitish discolouration of the oil (it's just a little dirty), and likewise no oil in the radiator fluid (none worth mentioning - there was a little in there after I swapped the rads but after flushing it has almost all disappeared - i guess it was from the donor car). Radiator fluid is an opaque green - a mix of coolant, water and rust/dirt.

Any more info needed, just ask. Thanks.

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Iain
Datsun Stanza GX
AKA "Stanley", "The Brown Bullet"
5 speed dogleg box, mechanical secondary throttle, Bluebird S2 radiator & fan, off-road spotties, paralysed nodding dog, "invisible dashboard", Volvo cold air duct

With my head because it had corroded from a coolant channel and directly through the combustion chamber sealing ring on the head gasket it did not mix with oil at all it just blew air and burnt fuel into the cooling system where it proceed to blowout my lower radiator hose and timing cover gasket adjacent the water pump.
This took ages until it finally let go (corroded bad enough).
The last time i had head corrosion troubles the coolant had corroded through to the exhaust port where the water was slowly dissapearing down the exhaust....

Heres a sequence of events i have learnt to take:
Start with the common and inexpensive things first.
e.g. make sure thermofan is blowing the right direction, check water pump/flow through radiator when engine upto temp and thermostat has opened, check temp guage working correctly, check ignition timing, flush cooling system, replace radiator cap, replace your thermostat, pressure test cooling system for leaks, get radiator core rodded or recored altogether if core is severely corroded and falling apart, then theres the dreaded headgasket....

Good luck.

Is it a new radiator or another 2nd hand radiator??
Sound like it could be a blocked or slightly blocked
radiator or maybe the impeller on the waterpump
has rusted away.

Matt Paroz

Timmed the motor again per spec.

make sure the bottom hose is not collapsing under load, Soft hose.

I drilled a small bypass in the thermosstat. There should be a jiggle vale in there for it already but maybe a tine air pocket is in there.

If not using water I assume the headgasket is OK

adjust the valve lash on the rocker arms. EZ!!!!!!!!!! .008 in .010 exhast hot

try pulling out the thermostat and putting it in a sauspan and boil it up to see if it opens

after a test drive last night, I reckon it could be the timing... i replaced the distributor points a few days ago, but I don't know how to adjust them. Could someone please help me out with this?

_________________
Iain
Datsun Stanza GX
AKA "Stanley", "The Brown Bullet"
5 speed dogleg box, mechanical secondary throttle, Bluebird S2 radiator & fan, off-road spotties, paralysed nodding dog, "invisible dashboard", Volvo cold air duct

Ian where is the thermo fan placed?
They work better if placed behind the rad & pull thro it.
Check that the rotation is correct.
Many a fan has been fitted with reverse rotation.
Even if rotation is correct the fan its self may be reversed.

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A little knowledge is a dangerous thing.
www.datsport.com

"R.I.P. Baz. 29 April 2022. Thank you for all your contributions to the Datsun community over the years. You will be missed." - OZDAT

thermofan is behind the radiator, rotation is correct and fan is pulling air thru the radiator.

_________________
Iain
Datsun Stanza GX
AKA "Stanley", "The Brown Bullet"
5 speed dogleg box, mechanical secondary throttle, Bluebird S2 radiator & fan, off-road spotties, paralysed nodding dog, "invisible dashboard", Volvo cold air duct

its timming. happened to me yesterday aftre putting the motor back together. on the dizzy there is a vac thing that changers timming under load. well mine was stuff keep advan and ever retarded it. put a timming light on it and rev it. mine was 15.c on idle and 45 at 2000rpm. and i was wondering y my car was getting hot so fast....
check it mate i got money on it that thats you problem.

gees...
45deg would cause serious problems...
yeah I've suspected that for a while, so I've been running it (mostly) with the vacuum advance disconnected. Which has helped, but it still overheats. I've adjusted the contacts properly now (I think) according to advice given by Hainz, so I'll give it a go tomorrow, and if it goes on the fritz, watch the classifieds nah, i'll keep trying to fix it for a while yet. Man I hope it's just the timing...

_________________
Iain
Datsun Stanza GX
AKA "Stanley", "The Brown Bullet"
5 speed dogleg box, mechanical secondary throttle, Bluebird S2 radiator & fan, off-road spotties, paralysed nodding dog, "invisible dashboard", Volvo cold air duct