Author Topic: radiator cap on automobile  (Read 3586 times)

0 Members and 1 Guest are viewing this topic.

Offline franksolich

  • Scourge of the Primitives
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 57340
  • Reputation: +2177/-171
  • ^^^apres moi, le deluge
radiator cap on automobile
« on: January 25, 2008, 06:32:39 AM »
We really need an automobile forum.

Anyway, an exchange of e-mails between franksolich and a local attorney:

Quote
When driving to [a small town] to pick up some money this afternoon, about six miles west of here, the temperature gauge suddenly soared upward.  I immediately stopped the car and opened the hood.
 
The radiator cap was half slipped-off, and so fluid was bubbling out of that.  One of the city councilmen, and then a state patrolman, and then a farmer, and then a South Dakota state representative, and then a hunter, stopped, but I told them to go on ahead; I didn't need anything.
 
After a few minutes, I screwed the radiator cap back on tightly, and had no problems all the way to [the small town], and all the way back here; everything including the gauges worked the way they're supposed to.
 
Question.
 
Why would the radiator cap pop off?
 
The last time anyone (which was myself) messed with the radiator cap was that night I ran out of gasoline, about two weeks ago.  I have since then driven more than 1000 miles since then, no problems.
 
It was -18 degrees F here this morning when I started the vehicle, to go to the county clerk's office.  I had considerable difficulty getting it started--the first time ever--but got it started.
 
And then nothing else until driving to [the small town] hours later.
 
What I am wondering is this--might I, that night two weeks ago, put the radiator cap back on, but only 99% back on--which was enough to not cause any problems.....until this really frigid morning?  Perhaps something froze, and loosened the radiator cap?
 
I didn't lose hardly any radiator fluid, having stopped quickly enough.  But at any rate, the vehicle is getting its regular routine oil change and all that in the morning (Friday morning), and I'll ask the mechanic about it.

The response of the local attorney:

Quote
When the air temperature is 18 below and you are driving down the highway, enough air is passing through that honeycomb material on your radiator to cause very rapid cooling.  That could cause your thermostat to go shut, which would result in very rapid warmup of the engine and the symptoms you describe.  When the thermostat opens up again, everything goes back to normal. 

I had an aunt once, who took a trip in Minnesota in very cold weather, and her thermostat kept going back closed on her, and then the overheat light would come on on a 25 below zero day.  The thermostat would open again, allowing all of the coolant to circulate, and things would go back to normal again until the cold air again caused the thermostat to close.  A thermostat serves to rapidly warm the engine, staying closed and not allowing the coolant to circulate.  When the engine warms, the thermostat opens. 

Sometimes it might be helpful to partially block (half of the radiator surface area) your radiator with a piece of cardboard so there is less cooling allowed and the thermostat then stays open.  That would have worked for my aunt if she had known to do it.  If you look at the front of some semis, they have controllable "curtains" in front of their radiators which they can open and close as driving conditions dictate.
 
The overheating you experienced would happen quickly and possibly created enough pressure in the system to pop the radiator cap off, especially if it wasn't quite seated in the first place.
 
You might have your coolant tested, too, to be sure you are getting freeze protection down to 30 below or better.  You might have a mixture of water and anti-freeze that is only protecting you to 15-20 below, especially if you haven't been keeping up with the anti-freeze, water mix in the radiator.  Those systems have become so reliable, quite a few people aren't checking them until there is a problem, a mistake which could cause major damage if your engine freezes up.  And an 18 below zero night like we had last night might do it. 

Usually, even a weak mixture will not freeze solid, but turn slushy, and then not circulate properly untill the engine heats it up.  The expansion forces that result from freezing liquid are awesome, will break almost anything, including concrete and steel.  It would destroy your engine, probably.
 
It is important to know how much freeze protection you have.

Well, the oil is being changed, and all that other good stuff, this morning (Friday morning) anyway, and I'll ask the mechanic about it.

There's always a first time in life for everything, such as two weeks ago when for the first time I ran out of gasoline (and thought it was something "bigger" than that), and now, for the first time in this life, the radiator cap popped off (for the record, the vehicle has been used considerably since that incident, and all seems to be fine).
Democrats: A bunch of rich people convincing poor people to vote for rich people by telling poor people that other rich people are the reason they are poor

Life is short, and suddenly you're not there any more.

Offline NHSparky

  • Hero Member
  • *****
  • Posts: 24430
  • Reputation: +1276/-617
  • Where are you going? I was gonna make espresso!
Re: radiator cap on automobile
« Reply #1 on: January 25, 2008, 06:36:53 AM »
Which is why most folks in REALLY cold regions cover their grills during winter.  If you have a new make vehicle, see your dealer or auto parts store for a cover.  Otherwise, cardboard works too.
“Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian.”  -Henry Ford

Offline MASHLover

  • Probationary (Probie)
  • Posts: 73
  • Reputation: +5/-1
Re: radiator cap on automobile
« Reply #2 on: January 25, 2008, 08:05:54 AM »
yep cardboard works wonders, it helps block that cold air coming in which would help to keep the engine warm and not cycle the thermostat.  It also helps to keep the inside warm because your heater also uses the water that goes through the engine.  If the water does not get very hot, your heater will not seem to be working as well when in all actuality its just the water does not get a chance to heat up enough.
formerly Striker

Offline Lord Undies

  • Hero Member
  • *****
  • Posts: 11388
  • Reputation: +639/-250
Re: radiator cap on automobile
« Reply #3 on: January 25, 2008, 08:34:26 AM »
You know, Franklin, being a southern boy who will only visit the frigid north in the warmth of Summer, this is all news to me.  I assumed, like a Pollyanna, that any industry that can come up with cruise control and power brakes would have, by now, come to grips with radiators and extreme cold driving conditions.   If nothing else, I think they would include a formfitting piece of cardboard in the truck by the spare tire.

Offline franksolich

  • Scourge of the Primitives
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 57340
  • Reputation: +2177/-171
  • ^^^apres moi, le deluge
Re: radiator cap on automobile
« Reply #4 on: January 25, 2008, 08:38:43 AM »
You know, Franklin, being a southern boy who will only visit the frigid north in the warmth of Summer, this is all news to me.  I assumed, like a Pollyanna, that any industry that can come up with cruise control and power brakes would have, by now, come to grips with radiators and extreme cold driving conditions.   If nothing else, I think they would include a formfitting piece of cardboard in the truck by the spare tire.

Well, they might, and I haven't noticed it yet in the trunk.

I got this vehicle on November 17; there's a lot of things I haven't noticed yet.

This reminds me of the previous vehicle, which I had gotten from the local John C. Calhoun--it was several months before I opened the trunk, only to find a virtual arsenal of firearms in it.

Of course, these were ruined firearms (bent barrels, broken stock, rusted, whatnot), because the previous owner used to use, for example, rifles as levers to pry something open.  There were nine busted, or partial, firearms in the trunk, nothing of any value, so on the recommendation of the sheriff, I tossed them.
Democrats: A bunch of rich people convincing poor people to vote for rich people by telling poor people that other rich people are the reason they are poor

Life is short, and suddenly you're not there any more.

Offline Carl

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 19473
  • Reputation: +1396/-98
Re: radiator cap on automobile
« Reply #5 on: January 25, 2008, 06:29:52 PM »
The thermostat situation really can`t happen as described becuse the bulb of it is in the coolant in the block,and once warmed up will stay open unless the entire coolant in the motor cooled to a point that allowed it to close.
You would notice the guage rising to temp then falling and so on plus the heat in the vehicle would be affected.
Regardless it wouldn`t make the cap come loose.
They have to be pushed down and turned to lock into position as well to load the spring which allows the system to pressurize.
If it overcomes that pressure the rubber seat on the bottom of the cap is pushed against the spring and it will open the filler neck so that coolant will escape into the recovery tank or be lost through an over flow tube.

My guess is that the cap wasn`t tightend past the locking dogs and combined with the extreme cold the radiatior partly froze preventing the coolant from flowing down through the core.
This caused the entire cap to push upwards and also without proper circulation the coolant heated very rapidly behind the sending unit for the guage.
This is always located at the top of the coolant circut where the coolant is the hottest.

Make sure it is a 50/50 mix and the cap is seated tightly.

Offline franksolich

  • Scourge of the Primitives
  • Global Moderator
  • Hero Member
  • *****
  • Posts: 57340
  • Reputation: +2177/-171
  • ^^^apres moi, le deluge
Re: radiator cap on automobile
« Reply #6 on: January 25, 2008, 07:21:23 PM »
The thermostat situation really can`t happen as described becuse the bulb of it is in the coolant in the block,and once warmed up will stay open unless the entire coolant in the motor cooled to a point that allowed it to close.
You would notice the guage rising to temp then falling and so on plus the heat in the vehicle would be affected.
Regardless it wouldn`t make the cap come loose.
They have to be pushed down and turned to lock into position as well to load the spring which allows the system to pressurize.
If it overcomes that pressure the rubber seat on the bottom of the cap is pushed against the spring and it will open the filler neck so that coolant will escape into the recovery tank or be lost through an over flow tube.

My guess is that the cap wasn`t tightend past the locking dogs and combined with the extreme cold the radiatior partly froze preventing the coolant from flowing down through the core.
This caused the entire cap to push upwards and also without proper circulation the coolant heated very rapidly behind the sending unit for the guage.
This is always located at the top of the coolant circut where the coolant is the hottest.

Make sure it is a 50/50 mix and the cap is seated tightly.

Damn, you're good.

That's exactly what the mechanic told me today; the cap was probably only 99% on, not 100%, and all was okay for a couple of weeks, until suddenly temperatures plummeted to -22 F and below.

The cap is 100% on now.
Democrats: A bunch of rich people convincing poor people to vote for rich people by telling poor people that other rich people are the reason they are poor

Life is short, and suddenly you're not there any more.