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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / December 2005Coolant Boiling Upon Shutoff
I have a friend with a 2005 GTO whose coolant is boiling when the vehicle is shut off. The engine temperature varies (per the Driver Information Center - in diagnostic mode) between 190 and 194 degrees when the vehicle is moving. When idling, with one fan running, the temperature goes as high as 229, then as the second fan kicks in and brings it down to about 206, then it climbs to 229, repeating the cycle. The temperature gauge (in the tradition of modern temperature gauges) does not move from its position of 3/8ths of full-scale during this temperature cycling. So far, so good. The problem is when the vehicle is shut off. After about 5 minutes, the coolant can be heard to boil - if you (carefully) grab a radiator hose, you can feel the bubbles. Sometimes coolant comes out of the overflow bottle. The overflow from the bottle happened when the ambient temperature was in the high sixties. When it does this, you wind up having to put in about a a quart or so of coolant once it cools. He took the car back to the dealer, who promptly took it in to look at it, but that day was cooler (about 55 degrees ambient), and it did not boil upon shutoff. The dealer pressure tested the system and found no leaks. I'm thinking radiator pressure cap, as the temperatures when running seem fine. The bottom line is that he is concerned about the long term effect of this behavior, as if the water is habitually boiling around the combustion chamber (E.G. area around the exhaust valves) upon shutoff, it's probably not a good thing for the metal around this locally overheated area. Any ideas? Thanks in advance, Jim To reply via e-mail, remove the "1" from the address given > I have a friend with a 2005 GTO whose coolant is boiling when the > vehicle is shut off. [quoted text clipped - 27 lines] > shutoff, it's probably not a good thing for the metal around this > locally overheated area. It could be due to a lot of things, but for $15 for a new cap, that is where I would start. > > I have a friend with a 2005 GTO whose coolant is boiling when the > > vehicle is shut off. [quoted text clipped - 30 lines] > It could be due to a lot of things, but for $15 for a new cap, that > is where I would start. ah- warranty, anyone!!! That $15 cap should be replaced by the dealer for free. ($15 for a CAP?!?!) Ted >> > I have a friend with a 2005 GTO whose coolant is boiling when the >> > vehicle is shut off. [quoted text clipped - 35 lines] > >Ted Thanks for the reply, gents. The car did not boil for the dealer techs. One said it "might" be the thermostat, but was unsure. What's more, the dealer does not stock the thermostat or cap (the cap is actually VIN #-specific). Two other dealers had the same story - special order only. He's probably going to to order both. The thermostat probably won't be too hard to get (probably the same as a LS2 Corvette), but something tells me that the VIN-specific cap (no doubt, some Coriolis-effect, Holden-only gem) will probably be a bit more difficult to obtain - one envisions Holden hiring Paul Hogan as a courier to canoe the $15.00 item across the ocean - he doesn't seem too busy these days ;) Thanks again, Jim > I have a friend with a 2005 GTO whose coolant is boiling when the > vehicle is shut off. Some cars retain power to the fan when the ignition is off so it can switch on if necessary when the engine is stopped. Does this one and if so does it work? -- Dave Baker Did they check to make sure someone didn't screw up and put the wrong mix of coolant/water in the radiator? It sounds to me like the engine is turned off which stops the cooling system (obivously) so the engine temp rises a bit. The water then boils because it's not the right mixture. Sam if all else has tested ok then you should drain about a pint of coolant and check its boiling temp. Old saucepan outside with a thermometer, bring to slow boil. >if all else has tested ok then you should drain about a pint of coolant >and check its boiling temp. Old saucepan outside with a thermometer, >bring to slow boil. Once again, thanks much to all who replied. As to the cooling fans running when the ignition is off, there is a sticker on the radiator shroud broadcasting dire warnings about keeping errant digits away from the fans lest they suddenly spool up when the engine is off, but we've never seen them engage with the engine off - even during temps in the upper-70s that were the norm when the car was new. Typically what happens at such temperatures is that both fans roar serveral seconds upon startup, then quiet down. As to the the coolant in the saucepan w/thermometer, we may as well give that a shot whilst we wait on Mr. Dundee to arrive with the cap - the thermostat will be in Monday. Just out of curiosity, at what temp would the proper mix (presumably 50/50) of Dexcool boil at in a pan? Additionally, I've ordered a IR thermometer which will hopefully show early next week, so temp readings with the engine off (and boiling) at various locations should be easy. The odd thing is it just started doing it after 8 weeks and 1,800 miles. Prior to that - and in warmer weather - it didn't do it. Thanks again, Jim > >if all else has tested ok then you should drain about a pint of coolant > >and check its boiling temp. Old saucepan outside with a thermometer, [quoted text clipped - 25 lines] > > Jim 50-50 ethylene glycol boils at 130C at standard sea level atmospheric pressure of 1013.25 millibars. The test will only tell you the percentage mix in open air at sea level, NOT what it does under pressure in your cooling system. It would be much easier just to use a float /density antifreeze checker, the kind with the little floating balls or the floating glass thing. The antifreeze tester is also somewhat cheaper than an autoclave and high temp IR vapor density sensor. On Sat, 03 Dec 2005 04:29:09 GMT, "=?x-user-defined?Q?=AB?= Paul =?x-user-defined?Q?=BB?=" <" =?x-user-defined?Q?=AB?= Paul =?x-user-defined?Q?=BB?="@houston.rr.com> wrote: >> >if all else has tested ok then you should drain about a pint of coolant >> >and check its boiling temp. Old saucepan outside with a thermometer, [quoted text clipped - 34 lines] >The antifreeze tester is also somewhat cheaper than an autoclave and >high temp IR vapor density sensor. Paul, Thanks for the tip. I agree in that you would think the coolant's behavior under pressure is (as a rule) of greater importance - mind you, if the cap is holding pressure. The dealer pressure tested the system itself, and it holds pressure. Since I'm none deep in autoclaves, and fresh out of high temp IR vapor density sensors, thefloat/density checker idea sounds good. I do wonder if they can accurately test Dexcool. Supposedly, these strips can test it - http://www.acustrip.com/specs/2-wayafauto.html Thanks again, Jim > On Sat, 03 Dec 2005 04:29:09 GMT, "=?x-user-defined?Q?=AB?= Paul > =?x-user-defined?Q?=BB?=" <" =?x-user-defined?Q?=AB?= Paul [quoted text clipped - 56 lines] > > Jim Strips are good. A usual way to test a cooling system's integrity is to remove the cap, screw on a hand pump tester with gauge, & pump it up while watching for leaks and the leakdown rate. They should also test the cap with the cap adaptor but it is somewhat difficult because of the lack of volume in the adaptor (assuming they have one for that type of cap). On Sat, 03 Dec 2005 16:52:16 GMT, "=?x-user-defined?Q?=AB?= Paul =?x-user-defined?Q?=BB?=" <" =?x-user-defined?Q?=AB?= Paul =?x-user-defined?Q?=BB?="@houston.rr.com> wrote: >> On Sat, 03 Dec 2005 04:29:09 GMT, "=?x-user-defined?Q?=AB?= Paul >> =?x-user-defined?Q?=BB?=" <" =?x-user-defined?Q?=AB?= Paul [quoted text clipped - 64 lines] >difficult because of the lack of volume in the adaptor (assuming they have >one for that type of cap). We went looking for strips today - to no avail. I suspect that the dealer may have pressure tested the system adaquately, but as you point out, the cap test can be a pain to do accurately. I was talking to an engine rebuilder today about another issue and brought up the problem. He said he suspected an air lock, and that the cap may have been what introduced it. He suggested using an IR thermometer to check the temperature around the coolant temperature sensor, as well as the temperature difference between the radiator inlet & outlet hoses - more than about 20-30 degrees is cause for concern, he said. Waiting on the IR thermometer, thermostat, and cap. I think I should be able to find the strips during the week. We'll be draining the system to put in the t-stat, and refilling it with 50/50 distilled water/Dexcool. As an aside, the dealer tech wasn't very concerned - he led the friend to believe that there is a light in the IP cluster that warns of genuinely excessive engine temperature - perhaps like the metal temperature sensor on the old (60's-70's) Cadillacs. Thanks again, Jim > We went looking for strips today - to no avail. > [quoted text clipped - 9 lines] > inlet & outlet hoses - more than about 20-30 degrees is cause for > concern, he said. Not true, this time of year I'd expect to see 100 degrees difference or more. Bob > Waiting on the IR thermometer, thermostat, and cap. I think I should > be able to find the strips during the week. We'll be draining the [quoted text clipped - 9 lines] > > Jim > <b1377@worldnet.att.net> wrote in message as well as the temperature difference between the radiator >>inlet & outlet hoses - more than about 20-30 degrees is cause for >>concern, he said. > > Not true, this time of year I'd expect to see 100 degrees difference or > more. > Bob On a car with an engine-driven fan, yes. On a car with electric fans sitting in a driveway without a lot of air moving over the radiator, I'd say 20-30 degrees is right on. >> <b1377@worldnet.att.net> wrote in message > as well as the temperature difference between the radiator [quoted text clipped - 8 lines] >sitting in a driveway without a lot of air moving over the radiator, I'd >say 20-30 degrees is right on. Thanks for the confirmation, Steve. I have found links that talk about this - - http://www.forparts.com/ICradiatorreplacement6.03.htm - http://www.motor.com/MAGAZINE/Articles/032000_14.html >> <b1377@worldnet.att.net> wrote in message > as well as the temperature difference between the radiator [quoted text clipped - 8 lines] > sitting in a driveway without a lot of air moving over the radiator, I'd > say 20-30 degrees is right on. If you want to play that game lets make sure the thermostat is closed in which case the temp differential will be close to zero. The point I was trying to make was that more than about 20-30 degrees is not cause for concern, and it can be much higher. Bob |
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