Running hot any suggestions

[Steveoen]

I have a 1978 280z with a 1981 zx motor in it so im thinking the problem is the motor is too much for the stock radiator is there any cheap suggestions to keep it cooler until i can afford the new aluminum radiator? Is there and silicon hoses or different fluids i can add the the system?

[CamH]

Cheapest solution: flush the coolant system. There is probably some junk in there which is making it not work as efficiently as it should.

 

If that's too much work, turn the heater and run the fan at full blast.

[kgriz]

There is a red juice called water wetter that seems to work pretty well for lowering temps.

[nosebleedZ]

IMO, the stock Z radiator is adequate for your setup, unless you are doing alot of stop-n-go city driving. Don't try to cure it with "Mechanic in a Bottle". Those are enhancement additives for higher demands such as racing, hot climates, or towing. Just as CamH said, start with the basics, like a flush & fill & SEARCH for the 4,000 or so overheating threads that are in the database here. Good luck!

[ozconnection]

I have a 1978 280z with a 1981 zx motor in it so im thinking the problem is the motor is too much for the stock radiator is there any cheap suggestions to keep it cooler until i can afford the new aluminum radiator? Is there and silicon hoses or different fluids i can add the the system?

 

You put a 2.8 engine into a car that had a 2.8. And the problem is.....? Too small a radiator? That doesn't make sense. Am I missing something.

 

To answer your question as what coolant to run, you have many choices and they should be based on your end usage. For most applications, your over the counter ethylene glycol anti freeze anti boil coolant will be more than adequate.

 

As mentioned, give the cooling system a flush. Good place to start right there.

[SHO-Z]

First try is to change out the thermostat. They do quit working. Is the coolant staying at a constant level? It the thermostat doesn't work and you are not loosing coolant install a new water pump.

[BluDestiny]

What is "running hot" for you? it should normally be around half way across if I recall. Do you mean that it starts warming up and it just keeps going all the way over? or does it stick at the 3/4 range?

[Steveoen]

What is "running hot" for you? it should normally be around half way across if I recall. Do you mean that it starts warming up and it just keeps going all the way over? or does it stick at the 3/4 range?

 

 

well apparently im a retard so nevermind

[Tony D]

"well apparently im a retard so nevermind"

 

Best to be thought an idiot, than to open one's mouth and remove any doubt.

 

 

I want to thank Blu Destiny for asking the 'proper' question: How hot is hot? Or more importantly, what temperature are you considering 'hot'? A meat thermometer from Wal Mart costs under $10, and sticking it in the water flow, or even in between the fins of the radiator will tell you FAR more than the gauge on the dash ever will.

 

I can't count the number of people who came to me 'overheating' only to find 180F water in the radiator, and a gauge on the third leg of the "M" in "TEMP"...

[LoneStarS30Z]

Well since we're on that topic, what exactly is considered too "hot"?

 

My Z constantly runs around 80C-85C (176F-185F) when I keep forward progress often enough, but once I sit in traffic for a little too long it'll start climbing into the 90C's, it once got to 99C and I was about to shut the car down and what for the green, but the light finally turned and my poo returned to my inner rectum. I've really contemplated upgrading the radiator.

 

Its always been my understanding that anything 100C or more is bad news.

Edited April 4, 2010 by xevenskyline

[Tony D]

That is dependent on environmental conditions and thermostat used. When you suck 72C air in the radiator, how cool should the water be coming into the engine? And as a result what will it be coming out of the engine, irrespective of thermostat rating...

 

I run a 72C thermostat, but during the summer when the air off the freeway going through the radiator is 72C from thermal layering above the black macadam....obviously I'm not going to run at 72C outlet!

 

Same goes for the situation mentioned---the car MAY rise to 100C with an 80C thermostat in it on a regular basis, especially on an off-ramp from the freeway, you suddenly go from 10,000+ cfm available of cooling airflow to nothing, but still have latent heat in the block and head from all that highway running.

 

Frankly, on my 260ZT, I have a problem getting up to operating temperature UNTIL I go driving and put a load on the car---at idle it lingers in the low 150's (62C). This is the same thing on the off-ramp. You come off and start putting out very little heat, but you have all that built up thermal mass to cool off from highway driving---but no flow over the radiator, and no flow off the pump. So you start circulating water very slowly. This means the temperature rise through the engine goes up---resulting in higher temperatures. At the same time, if there were adequate airflow across the radiator (a shorouded thermostatic stock fan will do this) this slower flow through the radiator will also result in lower temperatures into the engine, and shortly after the rise occurs, it reaches equilibrium and then starts coming down.

 

This is why people run 20 PSI caps---as long as you stop the spot-boiling in the head during this 'flash' rise in the temperature, you will not go runaway and make things worse. It will come up, it will go back down. how your pump circulates and how your radiator cools will determine how high it rises, and how long it takes to reach equilibrium and then start coming down again.

 

Personally, since I run the desert a lot, I run a 72C thermostat, and I rarely see 90C or above unless the thermal layering on the freeway is up there in temperature. It can be 130F on an 85 F sunny day, it does not have to be 'hot' to get overheated in SoCal. Conversely, in the midwest with all their aersols and UV blocking compounds in the atmosphere, you find Macadam temperatures much closer to ambient---maybe 105 on a 100 F day. Not a real stressor to the cooling system. If you are hitting these stratospheric temperatures where you don't get a DARK BLUE sky (meaning no aerosols and lots of UV Heating) you're cooling system is sorely out of maintenance interval and needs attention.

 

My car got 'hotter' in SoCal on an 85 F degree day than it did in 103 F days in the midwest. Thermal layer on the Baker Grade on an 85 F day was 130+, going across Iowa, Nebraska, and Illinois it was rarely more than 10F over ambient, if that. And when it rained----all bets off, back to 'left of center' on the gauge by a longshot. And that was with the A/C on all the way! Yeah, when you got an Omega multi K Thermocouple Box and a bunch of thermocouples from work taped all over your car (and an 8 year old kid to 'man the recordkeeping' through the whole trip---you learn a whole lot when you analyze the data afterwards!)

[LoneStarS30Z]

Good lord, I don't know what to say other than that was a lot more information than what I was expecting lol.

 

Thanks a lot though, I like understanding stuff like this, but I was asking what's a general rule of thumb of what may be considered as unsafe?

 

I'm in Arizona and my cooling set up consists of a L28ET with a stock radiator, 2 e-fans (pusher and puller), about 80% distilled water and 20% anti freeze with a 3/4 bottle of water wetter. Expectedly, the car does fine when I'm in motion, but the temp climbs when at a stand still. Rarely does it get into the 95C+ range, but I would like to see some consistency in the temperature, despite the fact I'm at a stand still.

 

I understand that when the car's moving it's gonna cool a lot more effectively from the incoming rush of air, but in my 2 previous cars, they held their own when sitting in one spot. Granted my other 2 cars had great cooling set ups, I believe my Z has room from improvement.

 

Hence why I'm wondering, at what point should I hit the panic button in my head and cool the car off immediately.

[Tony D]

I guess by SWAG you are running a 180F thermostat?

The question is not what temperature but how long will it rise to 95C? Does it stay there, or eventually fall back?

 

Electric fans are not that great, I do have two on mine, and I have my thermostatic control set to have them come on 10 F over where the engine will be running on a 110F day on the Palm Springs Grade (shoulder) at 30mph in 5th gear.

 

This is the lowest speed I want to consider activating the fans, any faster and you should have plenty of airflow.

 

I have a 170 thermostat. At 30mph in 5th gear my car runs around 175. My fans (2 x 10" Pullers) come on at 185, they will immediately cool the car back down to 165 and shut back off. Cycle repeats. Above 30 mph they do not turn on. The car will run cooler at 75mph than it does at 55mph (haven't figured that one out yet...)

 

If your car is 'running away' you either need a bigger fan, to flush/clean out the coolant system, or to run a lower temperature thermostat/rad cap/etc...

 

I found the fan switches that aren't adjustable are 'too late' switches. My car would get to 185, and by that time turning on the fans wouldn't cool down the car as effectively.

[LoneStarS30Z]

Usually when my temps rise is because I'm spending more time sitting in traffic than I am moving. When its starts getting really hot, say maybe 95C, if I can get in motion again it'll cool itself down to 90C and below in less than a mile. But if I'm stationary again it climbs.

[woldson]

The car will run cooler at 75mph than it does at 55mph

 

 

Oh man I'd love to take a couple stabs here.

 

1. Air flow changes at higher speeds

 

2. Air is able to over come crud in radiator.

 

3. A/F changes

 

4. A better union of all things, size rad, speed of flow through rad, (air and water), less micro boils in head etc.

 

5. Or just a noid trying to get you goat! Or sheep.

 

 

I know you are a world class trouble shooter, hence, you rarely get stumped on anything, so I just wanted to rattle the change in my pocket.

Edited April 7, 2010 by woldson

[zxtman]

...simple question, do you have a fan shroud?

[Tony D]

I don't see running cooler at 75 than 55 as an issue, so the 'I haven't figured that one out yet' was more a rhetorical question. I don't spend much time trying to figure out why it's working so well unless someone is paying me to figure it out! Common sense would say higher load would generate more heat, but my temperature won't start to rise until extended running near 'go to jail' speeds in CA...

 

Even then, it only comes up to 180/185F.... And that's with a three core radiator!

[aarang]

Just wondering, are you using one of the crap stamped impeller water pumps? I have had nothing but problems with those things. Get a genuine Nissan water pump with the cast impeller and see how you go.

[Tony D]

I would agree on the cast impeller comment. I have seen stamped steel items go away in less than 6 months after installation if the coolant has gone slightly acidic! I stopped using them altogether after seeing several do the exact same thing.

[woldson]

I don't see running cooler at 75 than 55 as an issue, so the 'I haven't figured that one out yet' was more a rhetorical question. I don't spend much time trying to figure out why it's working so well unless someone is paying me to figure it out! Common sense would say higher load would generate more heat, but my temperature won't start to rise until extended running near 'go to jail' speeds in CA...

 

Even then, it only comes up to 180/185F.... And that's with a three core radiator!

 

Understood, just an exercise in mind fun.

 

 

Also, I too have had problem with the stamped impellers, mostly the friction press, intermitenly coming loose.