Radiator Cap Mod (Cooling System Pressure)

[762mm]

Yesterday morning I've noticed some yellow-ish fluid that seemed to drip from under the truck onto the white snow beneath, and my first guess was that it was either prestone or possibly fuel (I filled up to the very top just minutes before). After inspecting the truck for more leaks later in the day, I came to to the conclusion that I was not leaking anything, at least visibly.

I nevertheless spoke with a professional mechanic (with many years of experience), just to find out what it might have been. He had told me that many smaller prestone leaks can be eliminated by removing pressure from the cooling system, and that can be achieved by cutting small notches in the lower gasket of the radiator cap (the smaller round gasket) or cutting the cap spring - this supposedly brings pressure to 0, and since the system is not pressurized, hoses do not swell up and don't leak. He stated that he runs all his vehicles (new and old) like that for many years, and has never had a problem. The only apparent side effect is the fact that the heater takes a bit longer to blow warm air.

I just did that mod to my Ex, and will monitor it closely... If anyone has any suggestions or remarks about this, please feel free to voice your opinion. I don't think my Ex has any leaks, but the idea of running a no-pressure cooling system to preserve the hoses and gaskets seems to make sense to me, even at the expense of waiting a bit longer for heat to kick in during winter.

 

[timleedude]

I wouldn't do that to my system. The pressure is there so that the boiling point of the coolant will be higher than without the pressure. I would return it back to normal and just make sure you check for leaks.

-Tim

 

[timleedude]

And since you have a hole in your radiator cap, the coolant reservoir tank will not work.. Excess coolant won't go into it, and won't return from the reservoir either.

-Tim

 

[410Fortune]

no do not modify your radiator cap on a late model vehicle with a coolant overflow resevoir!

the factory cooling system is 16# I believe (spring on radiator cap)
If your truck runs cool and you want to slow/stop small leaks you can get a 6-8 # cap that will fit, this is a better approach

My BII uses a $500 custom aluminum radiator, after a short time it developed two major leaks and its not covered under warranty (happy days happy days) to buy time until I can afford another $500 rad I switched to an 8 psi cap and the leaks really slowed down.

This is an old trick, and like stated lowering the pressure increases your chances of overheating, and by modding the cap as you did you have ruined the overflow resevoir functions (stock cooling system gets to 17 psi and the cap is pressed upwards, coolant flows into the holding tank, as it cools back down the reverse happens and the fluid is returned to the system, so no air is ever in the system)

If it is indeed your radiator cap that is leaking in the first place, it likely just needs to be replaced with a new OEM style unit, about $8

 

[old mechanic]

I understand his logic that no pressure will find less leaks. I have done that and put a lower thermostat in when my heater core was leaking but only until I changed the heater core. But if you have hoses that really swell up then they need to be changed not masked.
IMHO-Fix what needs fixing and keep it the way it is supposed to be.

 

[762mm]

Thanks for all your replies... I have already asked the mechanic I've mentioned about air in the system, and he said there shouldn't be any (I'll talk to him again tonight, and find out the exact logic behind it). If my engine starts running hotter than before or if there is any wierd symptoms, I'll bring it back to normal by buying another cap, maybe with a bit less pressure though.

I'll give the truck a test drive to work tonight, and see how it holds with the temperature and all... Will keep everyone posted. The guy says he runs all his cars like that (with overflow tanks), including a brand new Acura and has no problems or issues.

 

[BrooklynBay]

When I had overheating problems during the summer, with ATF pouring out of the front seal, one of the things I did was upgrade the radiator cap from 13 to 16 pounds. The old one had a bad gasket, and I kept losing coolant to the overfill tank.

 

[aldive]

Find a new mechanic; that one's advise is foolish.

 

[timleedude]

If you do go to a lower pressure radiator cap, realise that your boiling point of your coolant will lower. (Higher pressure, higher boiling point). I would just stick with the stock 16lbs and fix your bulging hoses or other problems. Most Cooling Systems are designed to run with 16lbs pressure. Be careful when you stick with non standard procedures. If a mechanic told me what your mechanic told you, I would say he's crazy and stop going to him and find another mechanic.

-Tim

 

[gijoecam]

Find a new mechanic; that one's advise is foolish.

Ditto!

The system will still burp itself, but the pressure is part of what prevents boilover, as already mentioned. Lower pressure = lower boiling point. In Northern Canada, it's probably not much of an issue, but in the majority of the 50 states, it'll be prone to boilover in the summertime.

-Joe

 

[762mm]

Hmm.. I spoke to him again, and asked for further explainations on the subject. He said that if you run a good (proper) mix of prestone and water, the slightly higher boiling point is not an issue... And as far as the temperature control is concerned, the thermostat takes care of that. He did admit that the pressure is there to run the cooling system at an optimal performance, but it's not a must.

I drove the truck to work and back yesterday, and it did not overheat or anything - the engine temp gauge was actually lower than it usually is. The overflow tank still seemed to work as it used to, even with the engine fully warmed. Having said that, I'm still taking all of your advice under consideration and will monitor the coolant levels, etc very closely.

Oh and by the way, my hoses and everything are all good... There was no leaks from anywhere even before the mod (with engine cold or hot), it must have been fuel that was still leaking after the fill-up that day. As I mentioned before, he said it helps in the eventuality of swollen hoses, but I never said I actually had any (that I know of) - I did the mod simply because I want to test it out and perhaps put less strain/wear on my cooling system over time. We'll see how it goes...

 

[F16pilotjd]

Was just searching for help with cooling system and saw this thread. Started out with deterioration of heat valve. Replace it and hoses. Then thermostat and water pump. Then new top and bottom radiator hoses. Pressure blew them off. I installed 2 new clamps on each and then replaced thermostat housing. Temperature remains in normal level but when driving it sounds like a loud fan or engine reving noise. Lately, I have been manually transferring from cooling resivoir to radiator and it works for a few days and then I have to do it again. Replace radios cap? At a loss. Will try any ideas

 

[koda2000]

Was just searching for help with cooling system and saw this thread. Started out with deterioration of heat valve. Replace it and hoses. Then thermostat and water pump. Then new top and bottom radiator hoses. Pressure blew them off. I installed 2 new clamps on each and then replaced thermostat housing. Temperature remains in normal level but when driving it sounds like a loud fan or engine reving noise. Lately, I have been manually transferring from cooling resivoir to radiator and it works for a few days and then I have to do it again. Replace radios cap? At a loss. Will try any ideas

Do not follow the advise offered in this thread. I replied to your other identical post (in another thread) on this subject. Every pound of pressure in the cooling system, added by the pressure cap/radiator cap, increases the boiling point of your coolant about 2-3 degrees F. It is a good thing, as long as your are using the cap specified for your radiator (usually 16 PSI). I explained the probable source of your pressure problem in the other thread.

http://www.explorerforum.com/forums/index.php?threads/pressurize-cooling-system.438264/

 

[F16pilotjd]

Thanks. Will buy a new cap anyway ($22) when back in states. Worth every penny not to be stranded for $22.

 

[koda2000]

Was just searching for help with cooling system and saw this thread. Started out with deterioration of heat valve. Replace it and hoses. Then thermostat and water pump. Then new top and bottom radiator hoses. Pressure blew them off. I installed 2 new clamps on each and then replaced thermostat housing. Temperature remains in normal level but when driving it sounds like a loud fan or engine reving noise. Lately, I have been manually transferring from cooling resivoir to radiator and it works for a few days and then I have to do it again. Replace radios cap? At a loss. Will try any ideas

Do not follow the advise offered in this thread. I replied to your other identical post (in another thread) on this subject. Every pound of pressure in the cooling system, added by the pressure cap/radiator cap, increases the boiling point of your coolant about 2-3 degrees F. It is a good thing, as long as your are using the cap specified for your radiator (usually 16 PSI). I explained the probable source of your pressure problem in the other thread.

Thanks. Will buy a new cap anyway ($22) when back in states. Worth every penny not to be stranded for $22.

Also, don't forget to test the hose from the radiator to the reservoir/expansion tank to make sure there's not a clog. I've seen it happen more than once.

Question: How do you explain having to add coolant directly to the radiator periodically if there's not a leak somewhere? You should never have to do this, as coolant should be drawn from the expansion tank if the system is sealed.

 

[F16pilotjd]

I siphon it out of the expansion tank as it fills up and put back in radiator. If I don't the car makes the fan noise until I do. So this fix may be just the think. Thank you

 

[koda2000]

I siphon it out of the expansion tank as it fills up and put back in radiator. If I don't the car makes the fan noise until I do. So this fix may be just the think. Thank you

If coolant goes into the expansion tank, but doesn't return on it's own, there's a really good chance there's a leak somewhere, which allows air to be sucked into the radiator as the engine cools down. The gaskets on the radiators plastic side tanks are usually where the leaks occur. This would be a separate issue from having too much pressure building up in the system.

 

[F16pilotjd]

Uggg. Makes sense. After cleaning resivoir, I will clean engine area and then when dry, look for any leaks. I will also do a pressure test which should identify any leaks correct? Or is there another more proven method? Thanks again.

 

[1998Exp]

This is an old thread, but one never stops being amazed at those mechanics who know better than the engineers that designed the car - not to mention being experts on thermodynamics without ever taking a high school physics class. I knew one or two who routinely removed thermostats from any car that they could put their hands on, "to prevent overheating."

 

[koda2000]

The best way to look for signs of leaking is to examine the bottom of the radiator and look for wetness and staining. I don't know what the setup is like on a 2007, but of my 2000-2001 Explorers there was a black plastic cover over the bottom of the radiator that was held on with 4 bolts. Once removed the leaking was pretty obvious.

Pressure testing is a good way to find leaks. Sometimes you have to add dye to help see where it's leaking.