2. Of running the car.i turned the car off. The cooling system is supposed to operate under pressure, it lowers the boiling point of the coolant. Coolant will be back in the radiator after it cools down. Under ideal circumstances, pressure should be stable. and i also losing coolant gallon a month. I changed the thermostat with the same result. I am still having the same coolant pressure issue and am rather stumped as to what the cause could be as clearly combustion gases are getting into the coolant system somehow. On the other hand, if the pressure was allowed to increase above 16 PSI the cooling system, including the hoses and even the radiator, could simply burst or even explode if the conditions were right. But what happens is when it is really cold outside, my coolant light flashes when I start my car. But if the pressure builds quickly to around 15 lbs the pressure is coming from one of the cylinders through the inner head gasket. the telltale sign is either milky coolant/oil or soot particles floating on the coolant surface. This can also show up as a coolant pressure … I was doing summer maintenance on my 2008 Gade XP, and when I unscrewed the coolant cap, the bottle was apparently still under pressure and shot coolant out. It is also possible that you have a thermostat stuck open, this will cause the low temp condition. The workshop guys say it might be an issue with the head gasket, and have said a minimum of 15 days time to get it fixed. With the car still on, listen to any humming sound that might be coming from the front part of your car. Also, the radiator shows constant pressure, for example, the car wasn't run for a week, then too when i opened the Radiator, the coolant spurted out. Has a Vortech S/C. And if coolant can get into your engine that means that pressure from the engine can get into your radiator. Still don't undersand why no circulation through the radiator though, or where the coolant goes when system under excessive pressure. Never lose sight of the fact that a liquid expands as it gets hotter. The “pressure” part is easy: if you heat a liquid or gas it expands. They showed me there was no more leak. Having to add coolant is an indication of a leaking head gasket. Because the head blew on the last one and was warped beyond repair. The issue is that when i go to check the coolant level by removing the radiator cap, the system is always under pressure. They put it on the lift after they replaced it and the engine was running and it was under pressure. When I filled the reservoir I noticed a leak coming from under where the water pump is located. I filled it up first thing in the morning before starting the engine that has been sitting over night. Motor runs and idles fine. I have a 2001 Honda Civic , D17A2 . If air is released when I turn the cap the system is holding pressure, but again, unlikely with a leak. Similar frickin' problem with my 5.0. if you blew a head gasket it will build pressure very fast and fill your overflow when cold , look for oil in the coolant or do a pressure check on each cylinder 0 0 Still have questions? And, any large increase or decrease should be investigated for possible mechanical damage. The reason is the increasing pressure on your radiator causing vibrations in the area. (1) negative pressure bc yesterday when at operating temperature, the tank was under 2 bars pressure after the cap regulated and released some excess pressure. As like any other liquid substance, the refrigerant contracts when it cools down. With the cap off I can squeeze the upper radiator hose and get some pretty big bubbles to come up in the tank. Jump to Latest Follow 1 - 4 of 4 Posts. When the engine warms up, expansion closes up the pathway, when the engine is shut off, and still warm, the pathway is still expanded closed, by the time the engine cools off, the coolant pressure has been relieved and there is do driving force to pass the two liquids either way. You know what causes pressure build up in cooling system and where the coolant goes after being expanded. I brought my 1 ton van home and the next day I found coolant on my driveway. I noticed my coolant reservoir was empty I filled it up and the next day empty again. Then, once my engine is warm after some driving, it turns off. Also, when i unscrewed the cap, coolant not only shot out, but more coolant flowed into the bottle (still below the cold line) When I came to check the coolant level in the system (cold engine) there was no coolant visible in the expansion tank. The head gasket, timing belt and water pump have all been recently replaced. Causes Of Low Pressure Reading – Consequences – Action Low oil level Parked overnight and the next cold morning the cold coolant and gas should collapsed and have negative pressure compared to ambient. Have you tested the freeze point of the coolant? Now this new engine (approx 24k miles on it) came with water pump and everything. The coolant level would raise too, so long as the air is not at the top of the radiator, but trapped somewhere else in the cooling system. I checked the coolant the other day after an 8 hr shutdown, and there was still pressure in the cooling system when I pulled the cap, so I don't think that coolant is being pushed somewhere after shutdown. Then I released all the pressure started the car and pressure slowly built to 15 psi , it took about 15 mins. New head bolts were used when the gasket was replaced. Also my bottom radiator hose is cold and the top is hot with a lot of pressure. Radiator under pressure, when COLD! It seems to be forced out of the tank which then appears to be empty, until that is the cap's taken off the tank and with a hiss the coolant returns to the tank coming up from the pipe below. If that liquid or gas is in an enclosed space the pressure of the liquid or gas will increase. Pressure in the system without heat is also an indicator. 1998 subaru coolant has disappeared 2 times with highway driving last June and November but it exhibited no leaks visibly or under pressure test. If the gasket is bad, there will be lots of pressure ONLY when the engine is warm and running. If your radiator system has a coolant leak, then you will be able to hear some sound coming from this part. 3. Note: that the sled was cold and had not been started in weeks. When removing the expansion tank cap, the system lets out pressure and the coolant … So, under cold start conditions, a “good” oil is one which gives stable oil pressure the fastest. The headgasket starts to go bad, coolant starts to enter your engine. Losing Coolant But good pressure test. Watched the temp creep up over about a … 1. I would imagine you'd have residual pressure after cooling back down. I usually let the car sit for a couple hours after driving, even a day sometimes, and I slowly twist the expansion tank cap. But mine are still solid when the engine is cold, meaning that the extra pressure is coming into the cooling system from somewhere. Especially if a car is a newer model, most people just assume everything’s OK, or that a light will show up on the dashb This is what happens, with the coolant, in the cooling system in your car. Found a hairline crack in neck of radiator under hose and replaced in december. It seems to have gotten worse with the cold - the lower the ambient temp, the more likely for an overnight coolant leak, '85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit) Just replaced the t-stat and put in 3row alum rad. So I've had this problem for a year now, haven't really taken care of it since the car still ran fine and everything. Here's a test.. With the engine cold, open your radiator cap, turn on the car, make sure the radiator is filled to the top. If you open the cap with the system still under pressure the pressure is released, whoosh, the hoses contract, and the level goes up a bit immediately. But what happens when it cools down again? – mike65535 Oct 10 '18 at 14:45 @mike65535 yep.. the real "danger" with opening the rad cap when the coolant is hot is that you are generally right over said cap (in order to open it) and that physics takes over, the reduction in pressure sees the coolant boil and you get a nice face full of hurty steam. When the engine is cold, the pressure of the cooling system is low and more coolant is required, and when the engine is warm the pressure of the cooling system is increased and therefore less coolant is required. Here is my problem, I have been loosing coolant from somewhere... no visable leaks anywhere from hoses or housing and … No smoke out tailpipes. The pressure in the cooling system builds to aprox 7 lbs at normal running temps looking around for leaks. What Happens When The Coolant Is Cold Again? swing (stayed 175 to 195) even when towing and the dealer said good to go.When the truck was cold and under pressure the level was under the middle line and when I took the cap off it would come up passed the line. The coolant system has lots of rubber hoses, which expand under the normal operating pressure (10+ psi) of the system, causing the level to drop a bit as the engine warms up. It still runs fine and everything while it's flashing. All I had to change was the inlet. Ok just a question 91 mustang gt.Did a pressure test on my radiator and coolant system, while cold I put about 16 lbs. Put flourescent dye in. Also, where the oil comes out, when you drain it, is NOT under pressure. Of pressure on it, it would slowly dropabout a pound every five minutes. Overflow isn't overflowing. No sign of coolant in the oil or on the ground after shutdown either. ... continue filling the raditor wlth water while the engine still on. DBW is right, there is always some pressure on the reservoir, even when cold. I have done a compression test also on all 4 cylinders and have a range of 148-150psi across all 4 which again I am happy with. Hi all, I have recently brought a Ford Focus 1.8TDCi Duratorq 2008. It’s been running pretty good but when I open the expansion tank cap when cold there is a fair amount of pressure released and if I open it too fast coolant will gush out. Most people don’t check the fluid levels in their cars as often as they should. I had a coolant leak, I brought it to tire Kingdom to have it looked at. Coolant reservoirs are required because engines go through cycles of expelling and absorbing coolant as they warm up and cool down. No apparent coolant in oil or vice versa. They told me it was my water pump and they replaced it. If it was a closed system as its meant to be then they should be pressurized when the engine is hot but then return to unpressurized when it cools again. I discovered the pressure in the cooling system when cold 5 months ago and I thought I had a problem.No coolant going away and no temp. I couldn’t tell if it was coming directly from there or not, could be a hose as well. Top 4 Bad Coolant Expansion Tank Symptoms. Crazy pressure in new top hose. Also my cooling fan was not turning on so I uncooked the fan sensor on the thermostat housing and bridge it. This is normal for all E46 (but not yours). Hi, I have a 1.0l 3 cylinder corsa D which I recently put a new engine in (like for like). 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Of radiator under hose and replaced in december exhibited no leaks visibly or under pressure, but Again, with.