M35 Overheating

[Cephas]

I had the m35 overheating heading down the M5 on Christmas Eve. The dash temp readout was showing the outside at about 36C.

It was OK doing 80, but much faster and the temp would spike.

Didn't appear to be leaking any coolant, but it was boiling in the overflow tank when I stopped to check it out.

I've read some people talking about getting the radiator flushed, and the mechanic I spoke to yesterday suggested that other m35 owners had been having issues with the thermostats.

Is there any know issue that causes this?

Should I be looking at getting the radiator replaced with something better?

Thanks.

Edited December 25, 2009 by Cephas

[_Ryan_]

Manual or auto?

Autos can be harder to get an off the shelf replacement rad due to the loop for bringing trans fluid up to temp.

Getting the standard rad flushed and a new OEM thermostat would be the first port of call IMO, unless M35's are massively under-cooled...(Waits for M35 owners to post)

[66yostagea]

There has been a bit about this lately. Maintaining a radiator's efficiency is as important, or more so, as regular oil changes. What is the point of changing oil every 5ks, if inbetween times the oil gets cooked and its lubricating properties are diminished?

When you change oil, flush radiator. Simple. Fill with good quality coolant. I said previously that my RMR30 radiator did 600ks and has now been in my R30 for two years. It is still clean as a whistle.

Before you go spending big bucks check the obvious. Radiator cap. Condition of fluid. Look to see if you can see crud in the tubes. There is a test you can do on the thermostat if you take it out. Is the fan working?

Last time I got a radiator, Celica, cleaned, I took it out to the rad place after getting a quote, $80. It was 80% blocked.

[zei20l]

its auto. all m35s are auto - not the new PM35s however, but i dont think one has even sold yet!

probably thermostat if its pushing out all the coolant into the overflow bottle and boiling it. or you have an air pocket/blockage. as mentioned above, get it looked it. worst case, get a new thermostat from nissan, or a nismo one.

there is nothing wrong with the standard radiator, only a handfull of people have had problems with the factory ones. mostly cracking or blowing hoses.

[_Ryan_]

its auto. all m35s are auto - not the new PM35s however, but i dont think one has even sold yet!

probably thermostat if its pushing out all the coolant into the overflow bottle and boiling it. or you have an air pocket/blockage. as mentioned above, get it looked it. worst case, get a new thermostat from nissan, or a nismo one.

there is nothing wrong with the standard radiator, only a handfull of people have had problems with the factory ones. mostly cracking or blowing hoses.

if its going to overflow, the rad cap could be shagged, always use OEM caps with OEM setups. rad cap can be functional and it can still overflow. as it should.

if the issue is on the freeway/at speed, more likely going to be blocked up than the fan, fan would be low speed. freeway speeds you should be getting decent airflow unless you tailgate BAD

Does it take a long time to heat up?

[Cephas]

It's only at freeway speed, so I think its unlikely to be a fan or waterpump as I think either of those would cause issue at any load.

[iamhe77]

I had the m35 overheating heading down the M5 on Christmas Eve. The dash temp readout was showing the outside at about 36C.

It was OK doing 80, but much faster and the temp would spike.

Didn't appear to be leaking any coolant, but it was boiling in the overflow tank when I stopped to check it out.

I've read some people talking about getting the radiator flushed, and the mechanic I spoke to yesterday suggested that other m35 owners had been having issues with the thermostats.

Is there any know issue that causes this?

Should I be looking at getting the radiator replaced with something better?

Thanks.

Yes, but you will not find an off-the-shelf unit with an in-tank cooler.

Your best bet would be to rip it out and get a custom unit made up using the original as a template and have the OE in-tank cooler ripped out and installed in the custom unit if you do.

While it is being made up, may I also suggest getting Nismo thermostat from RHDJapan (Good price & fast delivery).

Mine died after the week of 40degree days we had in Melbourne last year. Burst the top tank, bottom tank and also split some of the core.... I guess if you are gonna go, might as well make it spectacular!

M35's struggle to stay cool at the best of times, so a larger, more efficient cooling radiator can only help.

its auto. all m35s are auto - not the new PM35s however, but i dont think one has even sold yet!

probably thermostat if its pushing out all the coolant into the overflow bottle and boiling it. or you have an air pocket/blockage. as mentioned above, get it looked it. worst case, get a new thermostat from nissan, or a nismo one.

there is nothing wrong with the standard radiator, only a handfull of people have had problems with the factory ones. mostly cracking or blowing hoses.

I strongly disagree!

The standard radiator is well suited to the cooler Japanese climate, but it has a limited life over time in Australian Summers IMO

1700kg, AWD turbo wagon in 30-40degrees day in, day out for a solid 2 months? Yeah, I'm sure a small 15mm core radiator will do the trick in there.

Unfortunately I would not be surprised to hear of a couple of M35's overheating this summer... as mine and Jetwreck's did early last year.

Particularly those that have over 100,000kms on the clock.

Edited December 26, 2009 by iamhe77

[zei20l]

hmm thats not looking good for my stagea, its almost at 110k and we are heading into summer. but then again i dont drive it much lol

BUT, i did drive it all through last summer including those 40+ days and it didnt miss a beat. just kept using a crap load of fuel as per usual

[Cephas]

Are the VQ35 thermostats compatiable with the VQ25?

http://www.rhdjapan.com/nismo-low-temperat...yline-z33-55791

[KiwiRS4T]

I can't think of a good reason for getting a thermostat that opens earlier then spec. It is not going to stop overheating but on the other hand will result in operating temperatures that are less than optimal. There is no need to guess about the thermostat. You can take it out and suspend it in a jar of water at about 50deg (it should be closed) and add boiling water from a kettle down the side of the container a bit at a time while watching the thermometer. It should start to open just before the temp stamped on it and be fully open there or just after. If it does that there is nothing wrong with it. A crook one is usually stuck open or less often fails to open when it should. In that case you need another one of the same value.

Take your car to a radiator shop and they should tell you what the options are for free. They may not be able to tell you for sure why it is overheating but they can tell you if the header tank is cracked, how much it will cost to remove the top and bottom tanks and clean out the core, how much a replacement core would be and if Natrad list a thicker replacement. They could (for a charge) put a device on the radiator which will pressurize the system and see if it is losing presuure either from an observable leak (frost plugs, hoses, joints, heater element) or from the head gsaket or cracked head (not particularly likely - but you can look for oil in the water or water in the oil)

Then you can make an informed decsion.

[_Ryan_]

I can't think of a good reason for getting a thermostat that opens earlier then spec. It is not going to stop overheating but on the other hand will result in operating temperatures that are less than optimal. There is no need to guess about the thermostat. You can take it out and suspend it in a jar of water at about 50deg (it should be closed) and add boiling water from a kettle down the side of the container a bit at a time while watching the thermometer. It should start to open just before the temp stamped on it and be fully open there or just after. If it does that there is nothing wrong with it. A crook one is usually stuck open or less often fails to open when it should. In that case you need another one of the same value.

Take your car to a radiator shop and they should tell you what the options are for free. They may not be able to tell you for sure why it is overheating but they can tell you if the header tank is cracked, how much it will cost to remove the top and bottom tanks and clean out the core, how much a replacement core would be and if Natrad list a thicker replacement. They could (for a charge) put a device on the radiator which will pressurize the system and see if it is losing presuure either from an observable leak (frost plugs, hoses, joints, heater element) or from the head gsaket or cracked head (not particularly likely - but you can look for oil in the water or water in the oil)

Then you can make an informed decsion.

Only reason I did my thermostat was piece of mind, and it was 50$.

See if a replacement is listed here... http://www.jayrad.com.au/

[scotty nm35]

Ive cooked a freshly rebuilt engine due to a faulty new thermostat, I always check them now before fitting.

The dropping of a few degrees of temp with a different thermostat wouldn't make much difference would it? I can understand a new alloy radiator would be good protection but my stock one is still going strong.

[iamhe77]

Are the VQ35 thermostats compatiable with the VQ25?

http://www.rhdjapan.com/nismo-low-temperat...yline-z33-55791

Yep. One and the same.

[Cephas]

Unless the 'nismo' label is all talk on the thermostat they must have some reason for the lower openning temp. Any ideas?

Could it just be protection against heavy footed driving from cold?

Anyway, the car will be off to the mechanic, or the local NatRad, depending on who can see it first.

I want to take the car down the South Coast, and this kind of issue makes me nervious.

[iamhe77]

Unless the 'nismo' label is all talk on the thermostat they must have some reason for the lower openning temp. Any ideas?

Could it just be protection against heavy footed driving from cold?

Anyway, the car will be off to the mechanic, or the local NatRad, depending on who can see it first.

I want to take the car down the South Coast, and this kind of issue makes me nervious.

erm, to keep the engine cooler.

The Nismo stuff is designed as bolt on for track days, so in that instace doing whatever you can to keep the engine temp lower is a priority.

[Cephas]

erm, to keep the engine cooler.

The Nismo stuff is designed as bolt on for track days, so in that instace doing whatever you can to keep the engine temp lower is a priority.

Wouldn't it only keep it the temp lower for general running if it increased the flow rate through the radiatior?

As I understand it the main difference between the stock and nismo thermo would be the temp at which it opens, but that would only be 20C max right? and the engine temp should get though that in a few min.

Not trying to pick a fight, I'm just interested to know what effect one would have for normal driving use.

[iamhe77]

Wouldn't it only keep it the temp lower for general running if it increased the flow rate through the radiatior?

As I understand it the main difference between the stock and nismo thermo would be the temp at which it opens, but that would only be 20C max right? and the engine temp should get though that in a few min.

Not trying to pick a fight, I'm just interested to know what effect one would have for normal driving use.

No fight picked

You have to remember that once the thermostat has opened, the coolant is constantly taking the heat from the engine to the radiator where it is cooled and back into the engine again. (thus the need for a good radiator and engine fan to drag air through when stationary)

The thermostat only dictates at what temp that process begins, it is up to the quality of the coolant and the cooling efficiency of the engine to maintain that temp.

Edited December 29, 2009 by iamhe77

[KiwiRS4T]

As Peter says having a thermostat opening a few degrees earlier is going to make no difference on the track. With either thermostat its going to be fully open the whole time you are racing. If you need more cooling (and mine hasn't looked like overheating yet with the stock radiator) you need a bigger capacity radiator and/or oil cooler and a Nismo thermostat would be about as much use as a nismo radiator cap or gear knob.

[Cephas]

Ok,

The good news is it doesn't look like I've cooked anything

No oil or water where it isn't supposed to be, and the cooling system withstood a pressure test.

The thermostat was a bit 'sticky', so that will be getting replaced next service.

So far the main culprit is looking like the aftermarket radiator cap that wasn't holding pressure properly. so hats off to 66yostagea and RB_Ryan for picking that one.

[Cephas]

Well, it's still overheating, just not as much as before.

Its happy on the M4 / M5 / M7 now at 110, but overheats on some hills.

Climbing fast or slow doesn't seem to make much difference.

For instance, Penrith to Glenbrook, Stanwell Park to Bald Hill. Otford to Helensburg all had it a bit cranky.

Those hills had it just under 3/4 on the temp gauge. As soon as it levels out the temp gauge comes back to 1/2.

Any ideas on what I should be looking at next?