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Coolant leak issue

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7.4K views 10 replies 5 participants last post by  sttwoton  
#1 ·
Hello, first post here, but I was wondering if someone had any advice for me.

I'm the owner of a 2016 Focus ST diesel and I can't find the issue with my car. Ill provide as much information as I can remember. I'm not very engine or car savvy so if I've done anything silly, feel free to roast me, I don't mind the banter.

It started 1 month after servicing this year. I usually only drive a very short commute but on this occasion I was traveling long distance down the motorway when the oil temperature started to rise. Moments later the water temperature shot up to max and went into limp mode for about 2-3 seconds before returning to normal with oil temp still high. About a minute later I get a red warning light to pull over safely. Luckily I was very close to a services so I pulled into there where I let the engine cool down for around 20 minutes before starting her up again and driving off. I drove home later that day, keeping a steady speed of around 55mph with the heaters on full blast and I had no issues getting home.

I checked the engine coolant later that day and it was almost empty. I just assumed the guy who serviced my vehicle had not topped up the coolant enough so I did it myself. A few weeks later my water temps shot up randomly again before quickly returning to normal. My coolant was low yet again. I took it into a local garage and told them I was losing coolant, later that day he called me and said he couldn't find a leak.

Today I had another longer than normal commute so I topped up my coolant and off I went. I checked my heaters 10 minutes into my commute to make sure they were working, but they weren't(water and oil were normal running temp). I pulled over and turned off the engine. Before checking my coolant I turned the engine back on about 30 seconds later and the heaters were working perfectly.

Later that day I topped off my coolant yet again before driving home, and yet again the heaters didn't run warm after 10 minutes of driving so I pulled over, let it run idle for a while and still no hot air, even though water and oil temps were normal operating temp. I let the car cool down for about 10 minutes and opened my coolant cap and coolant leaked everywhere. I thought maybe I just overfilled it. I drove about another 5 minutes and still no hot air. I let the car cool down for 30 minutes this time and checked my coolant, which was empty again. I topped it up, again, turned the engine on and started driving home. Heaters were warm this time, keeping a steady speed of around 55mph for the next 50 miles . Closer to home I checked to see if my car felt any different by giving it some beans and all feels good.

Sorry for the long post but I feel like it may help identify the issue! The garage I originally took it to seemed friendly and had good reviews. He couldn't find the issue, but I can't say how much I actually looked for it. So if anyone knows where to go next to potentially get this issue fixed I would be very grateful!

Many thanks in advance.
 
#8 ·
Thanks for all the input guys. I phoned around some local mechanics to find out who would be willing to do a full diagnostic and repair quoting things like pressure testing etc, as some wouldn't or couldn't.

The root problem seems to have been a leaky thermostat that caused coolant to run low and overheat the engine. Exhaust gases made their way into the system due to head gasket failure. They sent off the head to be skimmed flat. Having new gasket, belt, water pump and thermostat. Total cost 1800. Expensive repair but seems worth it in the end.
 
#7 ·
Milky residue us just a sign and certainly isn’t always present as oil doesn’t necessarily get into the water with a blown head gasket/damaged head, thec rusty water is a bad sign too. Engine fine? Unfortunately at the moment it certainly isn’t and just because it starts and drives doesn’t mean a lot until you find the (possibly very serious) cause and any damage sorted. Sorry for being negative but your continued use in that condition is usually fatal for the engine. Never continue to run an overheating engine ever. If the heater (only got one?) doesn’t work that tells you straight away the water is low. If a car is overheating you stop and check the water level immediately before damage is done. If the oil is overheating that tells you the oil is picking up the excessive heat throughout the engine and no water is available for the oil cooler.

Leaking when you remove the water cap, where from ???
 
#5 ·
So no leaks underneath? Sounds like a possible head gasket failure and as it's been overheated numerous times now so the head will likely be warped. It's unfortunately likely already too late but you shouldn't continue to run it in this state, worse thing you could do. Might be a leak via the egr or similar but you need to get it diagnosed properly by a competent person. If it's head gasket a replacement engine might be an option. But you don't run modern engines if they're overheating, not for more than minutes, they will self destruct.
 
#4 ·
The oil cap is clean of any milky residue. The coolant is quite rusty looking which seems unusual considering its had about 10 litres so far over the last few weeks. When I've opened the cap after a full night there has been plenty of pressure still in the system, coolant rises and drops back down.
 
#2 ·
First, is there any mayonnaise under the oil filler cap, if so, it’s probably head gasket, these Peugeot diesel units can leak coolant from the egr cooler, which are a bit of a pig to change, buy a cheap sniff test kit from eBay, to determine whether there is exhaust gasses getting into the coolant system, which indicates head gasket, have a look on YouTube for videos on these problems.