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Enigma of Coolant Consumption - non Mercedes-Benz


tr4s

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Although it is not a Mercedes-Benz, my daughter's Pug 207 from 2012 is otherwise in fine condition. It has a full service history and is a basic but sufficient vehicle that is affordable to operate and insure. 1.4 litre 8-valve petrol engine
It is mostly used for short, localised trips.

It utilises a coolant.
During the first four months of ownership, there were no problems with the vehicle. However, in early December, when she drove it to Reading, which is around 50 miles away, the coolant tank was almost empty.
There were no obvious leaks seen on the drive after it remained stationary for many days.

Subsequently, I have refilled it on two occasions and entrusted it to the nearby automobile repair shop that I often rely on for servicing my daughters' vehicles. 21 days ago

Upon our purchase, a new thermostat housing was installed in the vehicle as part of the servicing it was due for. The garage conducted a pressure test on the housing and confirmed that there were no leaks.
Subsequently, they conducted a series of three heat and cool down cycles in their yard, during which there was no decrease in the level of the expansion tank.
They did not bill me as it did not consume any of their time and it seemed to need no more resources.
An air lock or bubble was detected but resolved on its own, and there have been no issues subsequently (the vehicle has been used for brief trips since then).

I went on a little excursion today, and upon my return, the temperature of the object was almost at its optimal level. Surprisingly enough, something noteworthy occurred...
The coolant has decreased by half from its original level.
The car is satisfactory in all other ways.

Given the current state of the coolant, it is probable that the head gasket is the next likely culprit.
I would appreciate any guidance prior to contacting the garage on Monday for a discussion.

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If there is no water present in the oil, it may be advisable to introduce a little amount of fluorescent dye into the system as a precautionary measure in case there is a minor leak that cannot be detected. This should be done before considering the possibility of a faulty head gasket. If there is a little leak at the thermostat housing or hose, the water will mostly evaporate by the time you lift the car's hood, especially if the engine is at operating temperature. If the head gasket were faulty, I would have anticipated some overheating or misfiring. However, I remain unconvinced that there is no leak. If the issue only occurs during long drives, it is likely that the thermostat has opened at that point. If the leak is small enough, it will likely evaporate on the side of the engine before it has a chance to drip onto the ground.

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Additionally, it is important to check whether the heater is emitting hot air and if it is worth examining the footwell area for any moisture, particularly at the higher sections at the sides, as this might indicate a potential leak in the heater pipes.

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Greetings

The heater is functioning well.
In my opinion, the moment when the thermostat completely opens is also the time when it takes a considerable amount of time to reach the desired temperature. Not indefinitely, but for a duration that exceeds my accustomed experience with our previous vehicles.

I will inspect for a leak by tactile examination, but the subsequent course of action involving the use of fluorescent liquid may be deliberated with the garage. I am hesitant to spend a substantial amount of money on a head gasket repair.

One could have expected that pressurising the system with positive air pressure for 15 minutes would have detected a leak.

Does anybody have any other thoughts?

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Perform a sniff test to detect exhaust gases in the coolant, which may indicate early indicators of water pump failure while the coolant is being expelled by the pump pulley. Has the pressure cap been inspected?

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Previously, I had a radiator that exhibited a leakage phenomenon when it reached a moderate temperature, neither too hot nor excessively cold. I discovered the issue when I started the vehicle's ignition after it had been idle for a while and drove it for a little distance before parking. This is not my usual routine, since I had just retrieved the car from a service and brought it back to my office parking lot, covering a distance of less than two miles. Fortunately, the parking lot had a gentle incline, and as I approached the front, a significant puddle or stream was seen, originating from underneath the vehicle. Upon seeing the potential risk of being left without coolant, I promptly drove home with great caution. However, upon arrival, I saw that the engine had already reached its optimal temperature and the leakage had ceased.

If I hadn't coincidentally found it, I suppose using fluorescent dye might have allowed me to locate it.

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Are there any visible discolorations on the radiator fins caused by the evaporation of coolant? What is the purpose of the expansion tank cap? Have any hoses been changed during a recent maintenance session, or are there any instances of old hoses breaking in the vicinity of the clamp?

When you mention that the coolant seems unclean, are you referring to its greasy appearance?

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A malfunctioning water pump is often the primary reason for gradual coolant loss. This is sometimes accompanied by a little leakage from the drain hole, which then evaporates due to the high temperature of the engine. Insufficient evidence. However, it is expected to be detected during a pressure test. If the previous condition is not met, as previously mentioned, it is advisable to conduct a gas analysis of the coolant.
 

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