My Nissan pickup (2.4L) uses a stock 13 psi rad cap. Nismo makes a high-pressure (18 psi) cap for, well... any Nissan owner who cares to spend the money. According to Nissan:
The Nismo radiator cap is a heavy duty radiator cap, which operates at 18.2 lbs (1.3 kg/cm) compared to 12.6 lbs (0.9 kg/cm) non-turbo and 16.8 lbs. (1.2 kg/cm) turbo Nissan OE(Original Equipment) stock caps. Made for vehicles that need more cooling than the stock radiator cap provides.
Now, I would REALLY like to have more cooling than the stock rad cap provides. Our summers down here are brutal, and I haul some heavy loads. However, I would assume that the "more cooling" comes at a cost.
So, besides the increased possibility of blowing a hose, what are the other risks/downsides?
Dangers of running a high-pressure radiator cap
- Thread starter HardbodyLoyalist
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i suppose theres a possibility of blowing out gaskets like the thermostat gasket for example easier, or waterpump seals. i dont know really.
I don't think there is any point to switching unless you are boiling over.
Now if you changed your coolant mixture to something like 25% antifreeze, and 75% water, and then went with the higher pressure cap, you probably would see somewhat better cooling. Water conducts heat better, and doesn't take as much work to pump. The higher pressure cap would allow you to run more water in the mixture without fear of boilover. And 25% antifreeze is sufficient to provide plenty of corrosion protection and keep the water pump seals happy.
The extra pressure will shorten the life of hoses and joints in the radiator.
No reason to add the higher pressure cap. With the 13 lb cap your boiling point is 251F. With the 18 lb cap your boiling point would be 266F.
Your headgasket will let go before 251F.
A higher pressure cap will not increase the cooling. It will just allow the engine to run hotter and at a higher pressure without boiling over. Perhaps not the best for long term service.
Perhaps an oil or transmission cooler would take part of the load off the radiator.
visvo has good advice, for a Florida car.
Maybe consider Redline's Water Wetter, as a suppliment.
I wouldn't use a high pressure cap.
You've all made some valid points.
The truck has a manual tranny, so no need for a cooler there.
I like the idea of the oil cooler. I'll have to think really hard, though, about where to mount it. Space is at a premium.
Concerning vizvo's recommendation: If I ran, say, 65% water and 35% Zerex G05 with an 18 psi cap, does anybody know how to calculate (a) the percentage increase in thermal conductivity of the coolant, (b) the boiling point, and (c) the freezing point? It's been many years since I took a course in thermo.
quote:So his head gasket will go before it boils over? What do you mean? What does the temperature have to do with the head gasket letting go?
Originally posted by Chris142: With the 13 lb cap your boiling point is 251F. With the 18 lb cap your boiling point would be 266F. Your headgasket will let go before 251F.
quote:You can calculate the freezing point, but it is easier to look at the chart found on most antifreeze jugs. How much heat would be removed by a given mixture depends on several factors and the calculations would get messy.
Originally posted by HardbodyLoyalist: snip.... If I ran, say, 65% water and 35% Zerex G05 with an 18 psi cap, does anybody know how to calculate (a) the percentage increase in thermal conductivity of the coolant, (b) the boiling point, and (c) the freezing point? It's been many years since I took a course in thermo.
JHZR2
Staff member
I see where youre coming from, however do you have a reason to think that you need extra cooling??? Does your temperature needle vary rom its normal point with the heavy loads in high heat?
If not, then I wouldnt worry about doing that; certainly you introduce a lot more variables that can have not so nice results.
What Id do for extra cooling and more beneficial results (IMO) would be to buy a sandwich adapter for my oil filter mount, and either run oil to a cooler, or to a bupass filtration system. Even the bypass will add more bulk oil and surface for cooling. Oil does have the ability to cool your engine, and having more bulk will reduce its degradation, allowing everything else to run in stride.
JMH
quote:To have a headgasket blow you don't need to have the engine boiling over. One most engines with alum heads anything over 230F it's possible to have it blow. So raising the boiling temp will not prevent a headgasket failure. Trying to make a cast iron block and alum head (Nissan)live @ 250F by upping the rad cap pressure won't work. It will blow the gasket at the same temp regardless of the pressure cap setting. The temperature is what causes the gasket to blow. The alum head grows but the cast iron block doesn't so the gasket gets smashed.
Originally posted by Tosh: [QUOTE] So his head gasket will go before it boils over? What do you mean? What does the temperature have to do with the head gasket letting go?
quote:Yes. The temp guage doesn't have actual numbers on it, so I have no idea what actual temperature I'm running. I do know, however, than during normal operation, the needle should run about 1/3 between the C and H marks. On a hot day in traffic, it runs about 1/2, and on a hot day, in traffic, hauling a 600 lb load, it will hit the H. It has never boiled over, but hitting that H mark can't be good. It's gotten to the point that on really hot days, I won't run my AC. I replaced the radiator and water pump last year (which helped a little). I've also recently replaced the thermostat and fan clutch (which didn't seem to make a difference). I think the issue is simply cooling capacity.
do you have a reason to think that you need extra cooling??? Does your temperature needle vary rom its normal point with the heavy loads in high heat?
1st thing you need to do is determin if the engine is actully getting that hot. If it is you have a problem somewhere.
Theres lots on Nissan trucks here in Ca pulling trailers loaded with ATV's up Cajon pass in August when it's 110F or hotter and they don't get into the red.
Adding 600lbs to your truck shouldn't make any difference.
Somethings wrong. Maybe the fins in the rad have lost their bond or the stat is acting up etc.
quote:Agreed... The seals on the radiator will be the first to go. Unless you have a cooling issue, your stock cap is sufficient. If you do have an issue, do all the entry level stuff first.. flush/fill with new coolant, thermostat, and a new stock cap. Don't overlook an erroneous sending unit giving a false high reading.
Originally posted by Chris142: The extra pressure will shorten the life of hoses and joints in the radiator. No reason to add the higher pressure cap. With the 13 lb cap your boiling point is 251F. With the 18 lb cap your boiling point would be 266F. Your headgasket will let go before 251F.
Try pressure washing the rad at a do it yourself car wash place. You may have a lot dirt built up in the a/c condenser if you have a/c or in the rad cooling fins.
When I was repairing my a/c system I had the condenser and rad out. You would'nt believe the dirt that was stuck in the fins. I pressured washed them and the coolant temp went down 15-20 degrees afterwards.
This thread is moving towards what I have always tried to do. Fix what is wrong with what you have and see if it works before modifying it. Great point on cleaning the radiator fins.
If other stock Nissans handle the heat, yours should too. On a truck, you may even be able to get at the radiator to clean it.
From my experience the only real benefit of a higher pressure cap is to prevent pinging. The cap, along with higher ratio of antifreeze (60-70% antifreeze) will reduce pinging. Hot spots and cavitation are reduced by this method.
if the cooling system doesn't create enough pressure to make your current cap vent then an 18# cap will make no difference.
Hardbodyloyalist,
I just went through the same thing with my wife's '88 Nissan pickup (with the z24i engine) this summer. I even created a thread about it here http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=24;t=003662#000000 . Basically, her gauge would climb to about 3/4's with the AC on while driving at highway speeds. Idle was fine. Everything in the cooling system got replaced, starting with the thermostat (several times), water pump with integral fan clutch (3 times), radiator cap, and radiator hoses. I flushed several times, including a "Super" flush you leave in for so many hours/miles of driving. It continued to do it. Advice on this board said the added thermal load from the Ac may have been overwhelming the radiator's capacity to cool. Got a new radiator, and problem solved. BTW, her truck's gauge has always gone to 1/2 way no matter what, except with the onset of this "problem". The gauges are not very accurate, meaning the "normal" is actually a broad range of temps.
I see you already replaced yours last year, but is it possible it got partially clogged during a flush or other engine work? Worth a check.
I've always thought timing could affect engine temp, so that may be something to check.
Aside from this issue, and normal wear items, her truck has been very good to us. She's the original owner, and maintenance the first few years was kinda hit and miss. Yet it keeps running... Our daughter may get it in two years for her first vehicle.
After re-reading one of your posts, it looks like you've replaced about all of the cooling system with the exception of the hoses. Your lower hose may be collapsing internally when under load when hot, restricting coolant flow. For just a few bucks, I'd change it and the top hose. May be the problem, and if it's not, you're out less than $20.
Hope this helps. If you need any more info, you can email or PM me. I have the Haynes and FSM for my wife's.
Dave
I just replaced the 23 year old radiator in my car with a sard aluminium radiator. It looks like a racing radiator..because the cap is a high pressure one. I tried fitting a standard cap on the sard radiator but it wont fit. So considering that the high pressure cap is "stock" on this radiator..will i be doing any damage to my engine ?
The reason i replaced the old radiator is because its badly coroded.
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