T-Cut
14th June 2016, 19:27
A recent thread discussing unidentifiable loss of coolant got me thinking about ways you might confirm if it's an internal leak. A bit of research and my background in chemistry has come up with this HowTo. I hope it may prove helpful to someone, sometime.
If you have a long term problem with a minor coolant loss that seems impossible to pinpoint externally, you may have an internal leak. This sort of failure can go unnoticed when little out of the ordinary is apparent. The engine runs normally at the correct temperature, the car drives is as it should, but there's this on-going loss from the cooling system. Naturally, this gets topped up at intervals but everything seems normal. But it's not and unless the problem is identified and fixed reasonably quickly, serious damage may result.
Sump contamination can happen when the head gasket fails between a coolant channel and an oil way. Coolant gets into the engine oil and the mixture becomes homogenised by the rapidly moving parts. This is assisted by the presence of additives in both the engine oil and the coolant. The oil contains surfactants/dispersants, for example to prevent sludge formation. Carbon particles are a major component of sludge, so engine oils have dispersants to keep it all in suspension.
Surfactants are partly oil-liking and partly-water liking molecules and cause small concentrations of water and polar materials (glycols) to disperse into the engine oil. They don't easily separate out on standing. Antifreeze also contains surfactants and chemical inhibitors, so a similar affinity exists here too. Heat this mixture to a couple of hundred degrees centigrade and strange things can happen. The sump becomes a chemical reactor.
At normal running temperatures a large proportion of the water getting into the sump will evaporate off, but that's not the problem. It's the other half of the mixture, the glycol and the inhibitors, that cause chemical changes in the oil. The most significant effect is a reduction in the ability to suspend contaminants like carbon, so sludge is promoted. Other changes result in a viscosity increase, so the oil doesn't flow so well around the passages and oilways. The worst case scenario is a loss of lubrication. In an extreme example, engine oil changes to something like black mollasses.
All this can and does happen in car engines, so another tool in a coolant loss investigation is worth having. The following describes a simple test used by engine oil analysts to help identify coolant contamination. It's based on a technique called paper chromatography. (Wiki info: https://en.wikipedia.org/wiki/Paper_chromatography). The effects of paper chromatography can be seen every day, beer spilled on a newspaper, a kid's fizzy drink mopped up with kitchen roll. When liquid mixtures are absorbed into paper, the ingredients separate into bands.
To do the test, you only need a suitable piece of paper and a couple of hours hours, maybe more, for the results to develop. The best paper for this is a filter paper disc as commonly used in labs. A small pack of 'qualitative' filter papers 9 - 10cm diameter can be bought for three or four pounds on eBay. But if you don't want to spend any money, a paper filter cone used for coffee will do a reasonable job. Even a business card has been used. Here's what you do.
You need one or maybe two drops of oil from the sump. The easiest way is to use the dipstick, preferably after the engine's been running so the sample is fully mixed and mobile.
Hold the paper horizontally and place a drop of the oil in the centre. If you need more than one drop, don't delay between them. The oil needs to go onto the paper all at once so there's a blob about 1cm across. Place the paper horizontally to one side and leave the chromatogram to develop. It might take an hour or two.
Capillary action causes the oil and everything dissolved in it to migrate outwards in a circle. Any carbon particles or sludge will not move very far from the original drop. If there's glycol in the oil, it will migrate at a slow speed, so after a while the oil will have moved out further than the glycol. They form circular bands.
Here's some diagrams of what you might find. Note that I haven't run this test myself, but I'm conversant with all forms of chromatography. So, the shapes and colours shown are my assessments made from the technical sources used.
Chromatograms
http://i5.photobucket.com/albums/y191/waveguide/Cooling_System_Stuff/Antifreeze_Stuff/Chromatography_zpsefx9fqdw.jpg
Anything other than the top example would be a cause for concern and require further investigation.
Synopsis:
Just 0.4% coolant in diesel engine oil is enough to coagulate soot and cause a dump-out condition leading to sludge, deposits, oil flow restrictions and filter blockage.
According to one study, glycol contamination results in wear rates 10 times greater than water alone.
Glycol reacts with oil additives causing precipitation. For instance, an important antiwear additive in motor oils, zinc dialkyl dithiophosphate (ZDDP), will form reaction products and plug filters when oil is contaminated with glycol. This leads to loss of antiwear and antioxidant performance.
Glycol has led to cold seizure of engines.
Ethylene glycol oxidizes into corrosive acids, including glycolic, oxalic and formic acids. Acids cause a rapid drop in the oil's alkalinity (base number), resulting in an unprotected corrosive environment and base oil oxidation.
Oil balls (abrasive spherical contaminants) form from the reaction of calcium sulfonate detergent additives (found in nearly all motor oils) and glycol contamination. These balls are a known cause of damage to crankcase bearings and other frictional surfaces within an engine.
Glycol contamination substantially increases oil viscosity, which impairs lubrication and oil cooling.
References
http://www.machinerylubrication.com/Read/133/radial-planar-chromatography-oil
http://www.machinerylubrication.com/Read/223/photometry-engine-oil-soot
http://www.machinerylubrication.com/Read/499/blotter-spot-method
Disclaimer:
You are responsible for any work or modifications carried out on your car and you undertake any such work at your own risk. Neither The 75 and ZT Owners Club nor the original author of these How-To's can be held liable for anything that may happen as a result of you following these How-To's.
Any modifications should be reported to your insurance company.
TC
If you have a long term problem with a minor coolant loss that seems impossible to pinpoint externally, you may have an internal leak. This sort of failure can go unnoticed when little out of the ordinary is apparent. The engine runs normally at the correct temperature, the car drives is as it should, but there's this on-going loss from the cooling system. Naturally, this gets topped up at intervals but everything seems normal. But it's not and unless the problem is identified and fixed reasonably quickly, serious damage may result.
Sump contamination can happen when the head gasket fails between a coolant channel and an oil way. Coolant gets into the engine oil and the mixture becomes homogenised by the rapidly moving parts. This is assisted by the presence of additives in both the engine oil and the coolant. The oil contains surfactants/dispersants, for example to prevent sludge formation. Carbon particles are a major component of sludge, so engine oils have dispersants to keep it all in suspension.
Surfactants are partly oil-liking and partly-water liking molecules and cause small concentrations of water and polar materials (glycols) to disperse into the engine oil. They don't easily separate out on standing. Antifreeze also contains surfactants and chemical inhibitors, so a similar affinity exists here too. Heat this mixture to a couple of hundred degrees centigrade and strange things can happen. The sump becomes a chemical reactor.
At normal running temperatures a large proportion of the water getting into the sump will evaporate off, but that's not the problem. It's the other half of the mixture, the glycol and the inhibitors, that cause chemical changes in the oil. The most significant effect is a reduction in the ability to suspend contaminants like carbon, so sludge is promoted. Other changes result in a viscosity increase, so the oil doesn't flow so well around the passages and oilways. The worst case scenario is a loss of lubrication. In an extreme example, engine oil changes to something like black mollasses.
All this can and does happen in car engines, so another tool in a coolant loss investigation is worth having. The following describes a simple test used by engine oil analysts to help identify coolant contamination. It's based on a technique called paper chromatography. (Wiki info: https://en.wikipedia.org/wiki/Paper_chromatography). The effects of paper chromatography can be seen every day, beer spilled on a newspaper, a kid's fizzy drink mopped up with kitchen roll. When liquid mixtures are absorbed into paper, the ingredients separate into bands.
To do the test, you only need a suitable piece of paper and a couple of hours hours, maybe more, for the results to develop. The best paper for this is a filter paper disc as commonly used in labs. A small pack of 'qualitative' filter papers 9 - 10cm diameter can be bought for three or four pounds on eBay. But if you don't want to spend any money, a paper filter cone used for coffee will do a reasonable job. Even a business card has been used. Here's what you do.
You need one or maybe two drops of oil from the sump. The easiest way is to use the dipstick, preferably after the engine's been running so the sample is fully mixed and mobile.
Hold the paper horizontally and place a drop of the oil in the centre. If you need more than one drop, don't delay between them. The oil needs to go onto the paper all at once so there's a blob about 1cm across. Place the paper horizontally to one side and leave the chromatogram to develop. It might take an hour or two.
Capillary action causes the oil and everything dissolved in it to migrate outwards in a circle. Any carbon particles or sludge will not move very far from the original drop. If there's glycol in the oil, it will migrate at a slow speed, so after a while the oil will have moved out further than the glycol. They form circular bands.
Here's some diagrams of what you might find. Note that I haven't run this test myself, but I'm conversant with all forms of chromatography. So, the shapes and colours shown are my assessments made from the technical sources used.
Chromatograms
http://i5.photobucket.com/albums/y191/waveguide/Cooling_System_Stuff/Antifreeze_Stuff/Chromatography_zpsefx9fqdw.jpg
Anything other than the top example would be a cause for concern and require further investigation.
Synopsis:
Just 0.4% coolant in diesel engine oil is enough to coagulate soot and cause a dump-out condition leading to sludge, deposits, oil flow restrictions and filter blockage.
According to one study, glycol contamination results in wear rates 10 times greater than water alone.
Glycol reacts with oil additives causing precipitation. For instance, an important antiwear additive in motor oils, zinc dialkyl dithiophosphate (ZDDP), will form reaction products and plug filters when oil is contaminated with glycol. This leads to loss of antiwear and antioxidant performance.
Glycol has led to cold seizure of engines.
Ethylene glycol oxidizes into corrosive acids, including glycolic, oxalic and formic acids. Acids cause a rapid drop in the oil's alkalinity (base number), resulting in an unprotected corrosive environment and base oil oxidation.
Oil balls (abrasive spherical contaminants) form from the reaction of calcium sulfonate detergent additives (found in nearly all motor oils) and glycol contamination. These balls are a known cause of damage to crankcase bearings and other frictional surfaces within an engine.
Glycol contamination substantially increases oil viscosity, which impairs lubrication and oil cooling.
References
http://www.machinerylubrication.com/Read/133/radial-planar-chromatography-oil
http://www.machinerylubrication.com/Read/223/photometry-engine-oil-soot
http://www.machinerylubrication.com/Read/499/blotter-spot-method
Disclaimer:
You are responsible for any work or modifications carried out on your car and you undertake any such work at your own risk. Neither The 75 and ZT Owners Club nor the original author of these How-To's can be held liable for anything that may happen as a result of you following these How-To's.
Any modifications should be reported to your insurance company.
TC