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Greeting Humans!

Lil Red is overheating on hot days. Not by a lot, but it does.

When I say "overheating" I mean the needle slowly climbs, to just over halfway with the A/C off on the highway,with the A/C on I got it up to 3 quarters before I chickened out. At 110 on the freeway it stayed at this temperature for about 20 minutes, and didn't start cooling back down until I got off the freeway and was back to 100km/h. At 100 or less I can modulate the A/C to keep the needle about middle - it takes about 5 minutes to get "hot", and about 5 minutes to get back down again.

I have put my under-tray back on, Coolant flush, Mania hose kit, New water pump and no coolant leaks.

A month or so ago it started heating up on the freeway as well (another hot day), didn't go over half, but I also didn't have working A/C then, and the under tray was off the car.

The radiator is the stock one, still black. I presume the freeway heating-up is due to freeways being wide and largely unshaded, so the "fresh air" I'm driving through is more "super-heated asphalt air".

Initially the plan was to get a 42mm ebay special radiator, and a reroute kit, throw them both on, and be content. After looking into the reroute kit, the price is a little higher than I'd imagined. (I'm a cheap-skate) But also the car is stock as far as the engine goes, so the factory cooling system should be able to keep up with the factory engine,AND I'm fairly certain it wasn't doing this last summer.

SIs there something else I've missed that should be checked first, or was "Australian Summer" just not part of the design brief when they were designing the cooling system?

Radiator is going to happen, but I'm on the fence about the re-route because the cost puts it into "cost/reward" category that's harder to justify to myself. It does seem like the "thing to do" and the rationale of the reroute makes sense, but also, cheap-skate.

So, let's see a show of hands for yea's and nea's for a reroute, I'll average your responses, and you'll decide for me. Or I'll do the complete opposite.

The standard radiator and cooling system on a stockish motor will take about 20 laps of circuit racing when it's 45 in the shade. So Australian summer was well within the design brief.

For a slow temp climb I'd be contemplating a thermosat that is only partially opening or else a radiator blockage. So, replace the thermostat (they're cheap) and take the radiator out and backflush it or get a radiator shop to test and clean it.

The re-route is a good idea but not essential if you're tracking it. Otherwise a waste of money on a stockish motor.

Yeah, agree shouldn't be overheating during an Oz Summer if all is serviceable.
Used to drive my NA6 & NA8 on the freeway between Canberra & Melb every Xmas/New Year holidays & temp never moved off about half.
For an cheap DIY coolant reroute, see wazman's how to on his NB8A - he used two Mackay rubber pipes (part numbers CH1530 & CH1805):
viewtopic.php?f=76&t=40239

I'd lean towards a wonky thermostat. Just be careful not to cross the threads on the housing, and buy a good seperate gasket.

I'd change the thermostat like magna said, super easy and cheap.
Mine was functioning fine when I changed it but it was almost white with calcification. Not hard to imagine it seizing up after not much longer in there.

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Are your fans working? Possible intermittent fault. The AC on kicks in the second fan, however at highway speeds the fan(s) don't add too much to the cooling capacity unless all the air is going around the radiator.

Is there anything reducing the air flow through the mouth, a grille perhaps?

Have you verified the temperature? A non contact thermometer on the radiator/hoses?

My thoughts to look at, in order of cost:


Check the fans are working, start the car let it idle (with aircon OFF) as it heats up the fan should kick in. If not, find the fault and fix.

Replace the thermostat, don't bother checking it just replace, it's about $20 for a new one.

Have the radiator flushed, it may have a blockage.
Buy some radiator flush stuff and follow the label. It helps loosen and remove any crap that's built up over time. In saying that, if it's reached the stage where there's a blockage it probably wont budge that. A radiator shop can do the job properly by removing the end tanks and using high pressure to blast the interior spotless.

Thanks team!

I did actually change the thermostat about 12 months ago, it's a trident one of unknown specification, is there a "more correct" one? (I walked into autobarn and said "thermostat please", and took the one they gave me)

I presume there's a right and wrong way of installing the thermostat, but if i had it in backwards it wouldn't work at all would it? (and I'd overheat really quickly)

I've made note to put them back in the same way they came out, but it's me we're talking about here...

I'm mildly confident it's not a blockage in the radiator - In the last couple of months I've put coolant-flush-additive-stuff through car and fully flushed it with the hose in every direction with the water pump & thermostat off: Put hose in a hole, run water until clear water comes out somewhere else, put hose in a different hole, repeat until everything is running clear water and I'm out of holes. I was surprised how long to took to get all of the old coolant out of the block - I did the same process for the radiator.

As for the gasket, I'm using a metal one sandwiched in some RTV Blue. Now I know how to RTV properly, it doesn't leak.

I will double check the fans. They were working "the other day" (was 14deg, put it back to 10deg, changed the timing belt, then put it back to 14deg after deciding it wasn't going to explode)

I have not verified the temps other than to put my hand on the top rad hose and discover that, yes, it is bloody hot, and touching it is a bad idea.

Oh, and nothing in the mouth - Currently a few dead bugs in the A/C condenser, but most of those are fresh and they get pressure-washed semi regularly - and the number plate is mounted above the mouth instead of in it.

I had to replace the thermo fan on mine due to an intimitant fault. (Worked when testing it then would die when in the car).

1. Thermostat (you've done the rest anyways, complete the job and finish the coolant system overhaul. That's why step 1.)

2. Check fan and replace if necessary. (Can use the air con fan motor from a n14 pulsar, if that is any cheaper for you)

3. Fit your new 42mm ebay radiator already ya cheapskate!
You're doing it anyway. Why waste time and money on the 100 year old unit when you are getting a replacement.

Hope you get it sorted soon

Have a receipt for the autobarn thermostat?
Maybe it's incorrect and wants to open at a higher temp?
I only ask because the local repco has given me incorrect stuff based on their computers before.

Doubt you would've put it in the wrong way, the jiggle pins might be a bit off but I'm not so sure that's really an issue on the 1.6 because the thermostat housing is vertical unlike the 1.8.

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Can confirm both fans are working with A/C on, and one is working when it's up to temp (just checked) and there is a good amount of air being sucked in the mouth when the fans are spun up.

I've a rough idea where the receipt for the t'stat is, but the autobarn receipts tend to heat-fade very quickly in my 'initial receipt storage area' (glove box) so it's probably a white sheet of paper by now....

I don't think the t'stat is in backwards, the fan didn't stay on for too long once it came on, so that tells me coolant is flowing at least a little bit to trigger the fans back off.

I just called Natrad in Perth (local shops all decided it's hometime already) and they quoted me $120 to do a full dissection and clean on my 25-year-old unit if I bring it in, where as the ebay special is $160, so "new rad" it is on that front.

I'll grab a new t'stat tomorrow and order the rad tonight, and sometime next week my entire cooling system will be less than three months old!

Stand by for a post in a week either confirming success, or rambling for hundreds of words about things normal mechanics know not to do

Thermostat should be in the correct way, from memory they will only fit one way anyway.

GOOD NEWS EVERYONE!

Everyone that said "thermostat" was correct-ish. I was most correct with "It might be backwards"....

You can indeed install a thermostat backwards. The correct way (According to the autobarn bloke) is "guts to motor". If you look at the stamping on the t'stat there will also be a "to rad" and an arrow pointing to what should be the direction of the radiator. Flow direction, not literally "over there" (just in case you're as special as I am, hopefully you're not )

It will indeed make the car slowly overheat, I'm guessing the flow/pressure of the water system is low enough to allow the t'stat to open at least a little bit.

I put the new t'stat in anyway.

I'm still an idiot.

Didn't order the rad because I decided to book in for a HR license and maxed out the daily limit on my card. Lucky! I'll see if "correct t'stat orientation' solves the issue.... /facepalm