Yet Another Radiator Cap Pressure

**mongobread** · September 12th, 2014 10:40 PM

Hi to all,

I know this has been discussed before, and I've already done a lot of back reads of the threads and research in the internet.

But I want to know and want to get answers specific to the details below for more clarity:

Engine: 4g15 carb
Status of Radiator: Old/Newly overhaul/re-patched 2 times because of leak
Radiator Cap: Circuit, Silicone Type (daw) is 0.9
I bought another Cap which is federal mogul 1.1
Thermostat housing: Corroded yung kinakabitan ng hose and I see white powder sa connection nya sa engine.
Coolant: I used 2 liters of premix halvoline long life coolant, pinkish stuff before the overhaul. Now I'm running mineral water not distilled dahil yun lang avail after overhaul. I plan to use coolant 50/50 Peak brand mix w/ distilled but I'm opting to get brand new radiator at dun ko na lang gamitin.
Hoses: Looks old and I don't know the age since I got the car November 2013.
Water Pump: Looks old and I don't know the age.
Water Status: Inside the radiator I see glittery particles na parang metal shavings. It doesn't have oil in it so I know my head gasket's not blown. My mechanic confirms it.
Engine: Parang masyado mainit kahit 1/4 lang temperature. Firewall is hard to touch pag afternoon tirik araw, even the sides of the front strut mounts.
Radiator Fan: Rekta Fan
Thermostat: None
Thermoswitch: disabled or sira na ata kaya hindi na naka-connect
Temp Sending Unit: Replaced / Bnew

I have full service manual of the engine and here's the book says:

Radiator Cap
Main Valve opening pressure = 81.4-108 kPa (11.8 - 15.6 psi, 0.83-.1 kg/cm*)
Vacuum valve opening pressure = -6.86 kPa (-1.00 psi, -0.07 kg/cm*) or less

Now here's what I need clarity:
I read that increasing the pressure increases the boiling point but make sure there's no weak points in the cooling system.

I used 0.9 after the overhaul but I read na 1.1 increases boiling point.

Now based sa specs ng book I'm allowed to use 1.1, but based sa nabasa nyong status ng cooling system do you think I should stick to 0.9?

Thanks in advance.

**saksidriver** · September 12th, 2014 11:03 PM

Kung ano yung stock yun ang gamitin mo. Kung hindi ka naman nagpalit ng thermostat. radiator cap naka depende yan sa thermostat. Stock thermostat = stock radiator cap. Kung wala ka thermostat, lagay ka.

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**mongobread** · September 12th, 2014 11:31 PM

Originally Posted by saksidriver

Kung ano yung stock yun ang gamitin mo. Kung hindi ka naman nagpalit ng thermostat. radiator cap naka depende yan sa thermostat. Stock thermostat = stock radiator cap. Kung wala ka thermostat, lagay ka.

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Poorly maintained ang kotse when I got it. It has 0.9 cap in it, the service manual says I can go 0.83 to 1.1 as stated here:

Main Valve opening pressure = 81.4-108 kPa (11.8 - 15.6 psi, 0.83-.1 kg/cm*)

I do plan to get thermostat sir and thermoswitch.

And here's the book says:
Thermostat
Valve opening temperature = 88 +/- 1.5 degrees celcius (190.4 +/- 2.7 degrees farenheit)
Full-opening temperature = 100 deg c (211 deg F)
Valve lift, fully open = 8 mm (0.31 in) or more
Identification mark = 88 (Stamped on flange)

What I want to get clarification is that should I go 1.1 cap to improve boiling point to fight against init ng pinas? Or I should go 0.9 dahil may edad na yung radiator at panay leak kaya re-patch pa rin after overhaul (under warranty kaya free patch)

What I have posted is stock cap is 0.83 - 1.1 caps is acceptable.

**dr. d** · September 13th, 2014 01:54 AM

Originally Posted by mongobread

Poorly maintained ang kotse when I got it. It has 0.9 cap in it, the service manual says I can go 0.83 to 1.1 as stated here:

Main Valve opening pressure = 81.4-108 kPa (11.8 - 15.6 psi, 0.83-.1 kg/cm*)

I do plan to get thermostat sir and thermoswitch.

And here's the book says:
Thermostat
Valve opening temperature = 88 +/- 1.5 degrees celcius (190.4 +/- 2.7 degrees farenheit)
Full-opening temperature = 100 deg c (211 deg F)
Valve lift, fully open = 8 mm (0.31 in) or more
Identification mark = 88 (Stamped on flange)

What I want to get clarification is that should I go 1.1 cap to improve boiling point to fight against init ng pinas? Or I should go 0.9 dahil may edad na yung radiator at panay leak kaya re-patch pa rin after overhaul (under warranty kaya free patch)

What I have posted is stock cap is 0.83 - 1.1 caps is acceptable.

I don't think your choice of cap is the cause of overheating. Look for another cause.
In some cars, water pump failure is manifested by a leak and not primary overheat.

**mongobread** · September 13th, 2014 02:05 AM

Originally Posted by dr. d

I don't think your choice of cap is the cause of overheating. Look for another cause.
In some cars, water pump failure is manifested by a leak and not primary overheat.

Sir hindi po cause of overheat question ko:

I read that increasing the pressure increases the boiling point but make sure there's no weak points in the cooling system.

Now based sa specs ng book I'm allowed to use 1.1, but based sa nabasa ninyong status ng cooling system do you think I should stick to 0.9?

Simply put, can my current overhauled, 2 timed repatched radiator, & old hoses with no thermostat in the engine plus the rekta fan setup can handle the increase pressure of 1.1 cap? (Note: I'm slowly trying to bring back stock setups to my 4g15 carb project. What I'm asking is the current setup)

**12vdc** · September 13th, 2014 02:24 PM

Your boiling point will remain the same, only difference is the cap will open at higher temps causing more pressure on the walls of cooling system. Since you mentioned the radiator is old and had history of leaks, that means the rad core couldn't withstand normal pressure range of your cooling system. It's your radiator that needs replacement-core is thinning due to corrosion. Cap opens(positive pressure) only when your'e on overheating condition. Since you are not overheating, then cap is not a factor.

Sabi ng radiator mo.. palitan mo na ako please. lol

I'd replace the leaky radiator, replace hoses, install back thermostat, and wire back thermoswitch to fan. From there if it still feels hot then i'd look somewhere else like correct coolant or waterpump (those glitters are telltale of worn pump or fragments from radiator core).

**jaypee10** · September 13th, 2014 05:29 PM

hindi issue ang radiator cap sa overheating maliban lang kung sira na talaga siya at tumnatagas na dun mismo sa cap ung tubig ng radiator mo.

1. buksan mo ung radiator cap at silipin mo kung nag si circulate ang tubig .kung hindi nag sicirculate.baka may thermotat pa siya,
subukan mo muna tanggalin ung thermostat.saka mo paandarin ulit para malaman mo kung umiikot ba ng maganda ang tubig sa makina mo papunta sa radiator..kung hindi na umiikot ng mabilis malamang water pump may problema.

**jick.cejoco** · September 13th, 2014 05:48 PM

Your cooling system should be sufficient in controlling the heat levels if the other systems are working right. Other possible causes of overheat include too lean of air/fuel mixture, intake vacuum leak, too advanced ignition timing, improperly bled cooling system, pump cavitation due to loss of pressure in the cooling system, too high octane fuel and rust/scale build up in the water jackets

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**niky** · September 13th, 2014 09:10 PM

Using a higher pressure radiator cap does indeed raise the boiling point of the water... which helps keep the coolant from boiling over... which helps prevent coolant loss in hot traffic.

Running pure water, will decrease the temp at which the coolant will boil, but not to the point where you should have problems.

Running with the radiator fan in "rekta" mode and without a thermostat, you're wasting a lot of gas... the car will be taking a whole lot longer to get to operating temperatures... which is bad for economy.

-

The metal shavings suggests that you might have a water pump problem, which is causing the high temperatures. Should also replace the hoses. Old hoses can expand, which decreases the pressure of the cooling system... which can lead to premature boiling of the coolant.

Given you've got shavings in t

**mongobread** · September 13th, 2014 10:16 PM

Originally Posted by niky

Using a higher pressure radiator cap does indeed raise the boiling point of the water... which helps keep the coolant from boiling over... which helps prevent coolant loss in hot traffic.

Running pure water, will decrease the temp at which the coolant will boil, but not to the point where you should have problems.

Running with the radiator fan in "rekta" mode and without a thermostat, you're wasting a lot of gas... the car will be taking a whole lot longer to get to operating temperatures... which is bad for economy.

-

The metal shavings suggests that you might have a water pump problem, which is causing the high temperatures. Should also replace the hoses. Old hoses can expand, which decreases the pressure of the cooling system... which can lead to premature boiling of the coolant.

Given you've got shavings in t

Sir bitin ata yung message mo.

Again sir, I've done my homework kaya nga po sabi ko unti unti ko restore yung cooling system. I already know what you have said and thanks for re-confirming.

My only question is that based sa mga nabasang details ng cooling system ko, should I be using 0.9 cap or 1.1 cap? I just want to confirm if I can use 1.1 kahit overhauled at matanda/weak na yun radiator at lumolubo yung radiator hoses ko.

But I think you've kinda answered my question when you mentioned hoses expand that leads to premature boiling. I think 1.1 cap gives more pressure sa system na pwedeng ikaputok ng hoses as I've read na use high pressure cap if there's no weak points in the system. Tama po ba?

Currently I'm back to 0.9 cap federal mogul brand..

My question is purely educational purpose po. For the record I'm self-learning car mechanics, DIY guy as a hobby and used 4g15 carb engine to learn. I'm slowly returning everything sa stock factors po.