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Discussion Starter #1 (Edited)
good evening my fellow Bimmer Owners. today i seek the help of anyone with knowledge. I will describe what seems to be a nearly impossible scenario, so get ready.

I have replaced so far:
- Water pump replaced
- Thermostat Replaced
- Temperature sensor Replaced
- New coolant Added
- Coolant System air bled
- Reservoir tank cap Replaced

A month ago i replaced the water pump because the old was squeaking. recently i replaced the head cover gaskets because of misfires across all cylinders, oil leaks, and air leaks. I also replaced the parking brake, so I managed to remove all of the lights from my dash "AWESOME" i thought.
In a 900 mile drive across my state my car's warning light came on for high tempt which is triggered at 120 deg. C. I pulled over and inspected noted the car was loosing coolant, added coolant and noticed the reservoir cap lost one of its 2 seals. came back some light came on another 5-7 times. so i thought the thermostat was damaged, so i replaced it. car overheated 2 more times and the third the yellow light of overheat was "RED" so i thought oh-oh.

I bought a new reservoir cap and temp sensor thinking about pressure in the system, nothing changed however. car still reaches 113 degrees, but after 30 minute ride, also i noticed if i shut off the ac it takes longer to reach 110 and if actually tends to go down. so you might be thinking "it might be the fan" well at around 100 deg Celsius the fan turns on, the AC blows ice cold, and the fan kicks it into high gear when it is about 110.

So you might also think "hmm clogged radiator", well i checked the radiator for cold spots only to find out how fast i can burn my hand, the whole thing seems to be working great. I bled the system for air but i seem to be having an issue with the auxiliary, however, the driver side vents get really hot when bleeding the system, so it works at least. the passenger side might not get hot because i am having an issue with the AC switches.

So next thing, check to see if the new thermostat is in bad shape, well let the car run to 105 without putting the reservoir cap on and well after burning half my hand i noted that the new thermostat indeed does open up at 105 flat.

Ok, so almost out of options, I went and got a block tester. Yes to check for exhaust gases in the coolant. So, NO the car is NOT LOOSING COOLANT like EVER. stupid i know but still did it. I got tonight the tester and the fluid, placed it to the reservoir tank, turned the car and let it warm up. Pumped the block tester and it remained blue, did it all the way until the thermostat opened and burned my hand, it came back negative, "good news" i thought, but **** i am back in square one, WTH is going on with my car.

At this point I am thinking of replacing:

- Heater valves
- Radiator
- Radiator fan

Any help will do, any ideas no matter how insignificant might help.

- ------things to note,
- i have a bad secondary pump - nothing to do with engine cooling
- I have a code for a butterfly (DISA) located in the air intake, it seems to be screwing up
- I have a code for circulating sensor damaged - things to with AC
- Also, car VERY recently developed a huge oil leak at the passenger side, front end near the bottom, i think below the chain cover. I think it might be the alternator support bracket i have hear about, Any ideas????
- :cry::cry::cry::cry::cry::cry::cry::cry::cry:
 

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ok so correct me if I'm wrong but I believe this vehicle has a self bleeding system!.. so number one if you do have air in the radiator or block or anywhere for that matter u can def be overheating and being that u have lost enough coolant to illuminate the red overheating icon u had air in the block as the water pump had no water to pump into the block. for this first issue I would disconnect the upper radiator hose from the radiator with the engine completely cold !!!! like literally first start of the day cold, hold it as high as possible to completely fill the block I have a 745i and u need to remove the thermostat but this will eliminate any air in the engine block then quickly and carefully reconnect trying not to spill coolant , u will spill some but that's ok because whatever is below the therm is what matters. I wouldn't take chances on a possibly faulty thermostat as a very inexpensive part can cause u a new engine so just buy the thermostat or u WILL regret it later, next with a helper to keep an eye on the temp warings inside the car get ur hands on an infrared heat laser thermometer they are relatively cheap and a great tool u will use for everything with it u can check your radiator at full operating temp properly for even heat distribution with the added bonus of not burning yourself! this is the only way to properly check your radiator as far as I'm concerned u can even borrow one if u don't want to spend the cash. with that said move on to the coolant tank it comes under a decent amount of pressure at operating temp and they do get hairline cracks which u wont notice until the engine is nice and hot what happens is a hairline crack develops and u slowly introduce air into ur closed system and also slowly expel coolant in the form of steam which will flow out of that crack sounds dumb but ive seen it with my own eyes!! I know u think ur not loosing coolant but BEING POSITVE IS ALLWAYS BETTER!! these cars are notorious for an oring leak at the temp sensor and the lower expansion tank hose check them AGAIN as u obviously had a leak before these issues, u have two sensors on your water pump clean them, u have a straight pipe under the intake manifold that leaks I know u think u don't have a leak but check it anyways in the process of elimination. just because ur coolant tank is full doesn't mean ur engine block is. your alternator is water cooled check it!!! don't assume anything and don't throw money at something that probally will end up costing u a few dollars in gaskets or orings. and yes I own a 7 which I love but also hate!! if u have checked everything and checked it twice do a leak down test to see if your cooling system holds pressure?? does it?? do a compression test to see if ur block is cracked between cylinders do u have less then 15 to 20% variance on all cylinders? check cooling system for oil and oiling system for coolant u may be getting coolant in your valve covers but not in your pan I know it doesn't sound logical but tell that to someone who hasn't run into that issue before because I have, if ur leak down and compression test come out good then don't and I repeat!!!! don't drive it because this is a blessing in that your engine is healthy and the problem lies somewhere else most definitely the cooling or oiling system if u continue to press ur luck then the repair bill will likely be more then another745 I hope u get the problem fixed because then u can float around town in class. I can list so many problems my car has it would fill two pages solid no kidding but as bad as people can make them sound the fact is it still drives around smooth and dependably with just about every tranny and engine problem known without any problems other then inconvenience ! THE REAL PROBLEM IS THROWING PARTS AND MONEY AT SOMETHING U DONT UNDERSTAND don't pay some guy who is gonna charge u crazy money just get well informed ask questions and I mean a lot obsess over it to the point u have exhausted all other options then leave it alone for a week and the answer will most likely come to u or show itself I hope u have another car to drive until then and if u have any other questions feel free to ask I'm sure others will have more clever answers but this is coming from someone who cant afford to pay anybody to work on my seven because the parts alone break my wallet [email protected]! lol I am also a mechanic for a living and these cars can fool me like nobodys business but once u get more info and more exp u will realize these cars only need to have your complete attention as to not break other stuff while working like 300 dollar sensors the actual labor turns out to be pretty dang easy they are just intimidating and yes sometimes u may need a special tool and once again I cant stress enough when I say don't go cheap on this car do it once and be done with it have a nice night and good luck
 

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Discussion Starter #5
ok so correct me if I'm wrong but I believe this vehicle has a self bleeding system!.. so number one if you do have air in the radiator or block or anywhere for that matter u can def be overheating and being that u have lost enough coolant to illuminate the red overheating icon u had air in the block as the water pump had no water to pump into the block. for this first issue I would disconnect the upper radiator hose from the radiator with the engine completely cold !!!! like literally first start of the day cold, hold it as high as possible to completely fill the block I have a 745i and u need to remove the thermostat but this will eliminate any air in the engine block then quickly and carefully reconnect trying not to spill coolant , u will spill some but that's ok because whatever is below the therm is what matters. I wouldn't take chances on a possibly faulty thermostat as a very inexpensive part can cause u a new engine so just buy the thermostat or u WILL regret it later, next with a helper to keep an eye on the temp warings inside the car get ur hands on an infrared heat laser thermometer they are relatively cheap and a great tool u will use for everything with it u can check your radiator at full operating temp properly for even heat distribution with the added bonus of not burning yourself! this is the only way to properly check your radiator as far as I'm concerned u can even borrow one if u don't want to spend the cash. with that said move on to the coolant tank it comes under a decent amount of pressure at operating temp and they do get hairline cracks which u wont notice until the engine is nice and hot what happens is a hairline crack develops and u slowly introduce air into ur closed system and also slowly expel coolant in the form of steam which will flow out of that crack sounds dumb but ive seen it with my own eyes!! I know u think ur not loosing coolant but BEING POSITVE IS ALLWAYS BETTER!! these cars are notorious for an oring leak at the temp sensor and the lower expansion tank hose check them AGAIN as u obviously had a leak before these issues, u have two sensors on your water pump clean them, u have a straight pipe under the intake manifold that leaks I know u think u don't have a leak but check it anyways in the process of elimination. just because ur coolant tank is full doesn't mean ur engine block is. your alternator is water cooled check it!!! don't assume anything and don't throw money at something that probally will end up costing u a few dollars in gaskets or orings. and yes I own a 7 which I love but also hate!! if u have checked everything and checked it twice do a leak down test to see if your cooling system holds pressure?? does it?? do a compression test to see if ur block is cracked between cylinders do u have less then 15 to 20% variance on all cylinders? check cooling system for oil and oiling system for coolant u may be getting coolant in your valve covers but not in your pan I know it doesn't sound logical but tell that to someone who hasn't run into that issue before because I have, if ur leak down and compression test come out good then don't and I repeat!!!! don't drive it because this is a blessing in that your engine is healthy and the problem lies somewhere else most definitely the cooling or oiling system if u continue to press ur luck then the repair bill will likely be more then another745 I hope u get the problem fixed because then u can float around town in class. I can list so many problems my car has it would fill two pages solid no kidding but as bad as people can make them sound the fact is it still drives around smooth and dependably with just about every tranny and engine problem known without any problems other then inconvenience ! THE REAL PROBLEM IS THROWING PARTS AND MONEY AT SOMETHING U DONT UNDERSTAND don't pay some guy who is gonna charge u crazy money just get well informed ask questions and I mean a lot obsess over it to the point u have exhausted all other options then leave it alone for a week and the answer will most likely come to u or show itself I hope u have another car to drive until then and if u have any other questions feel free to ask I'm sure others will have more clever answers but this is coming from someone who cant afford to pay anybody to work on my seven because the parts alone break my wallet [email protected]! lol I am also a mechanic for a living and these cars can fool me like nobodys business but once u get more info and more exp u will realize these cars only need to have your complete attention as to not break other stuff while working like 300 dollar sensors the actual labor turns out to be pretty dang easy they are just intimidating and yes sometimes u may need a special tool and once again I cant stress enough when I say don't go cheap on this car do it once and be done with it have a nice night and good luck
- Thank you and I will be taking it all into consideration. The car i keep checking it every day and the car is not loosing coolant from anywhere, and i did check the tube that goes to the water pump from the block and when i put them all back i made sure to put some approved silicone around it, I have no leaks coming from anywhere.

- Just last night i took it for a drive, when i reached 111 deg Celsius, i pulled over and inspected the system and it was fully pressurized and i do mean FULLY pressurized. The hoses were rock hard.
Then the second time i check both hoses for temp and both were running really hot, meaning the thermostat is fully functional and operating. I have witnessed the thermostat operating at 105, with the cap open, the water begins to pour from the tank so i seal it.

- NOTE: last night while inspecting the hoses, i noticed that the fan was blowing, however, I do have a question. I have seen some of videos on the 750li and on a 745i and i have seen that the fan SCREAMS like literally SCREAMING at full blast. my car does cool the ac and all but I have yet to hear my fan SCREAM, it blows fast but nothing like what i see on this videos.

https://www.youtube.com/watch?v=b2W4GkbBDg8

could this be my issue, since i cannot test the fan i do not know what the top speed of the fan is, but mine definitely does not do this.

- On another note i think my huge oil leak is coming from the oil pressure switch. I have finally parked the car for good with this issues, i will be doing a full engine clean with RGB and hoping nothing is wrong with the car.

- Thank you again and any input will do me great.
- I will check for the millionth time to for leaks but with the car not leaking coolant and holding pressure i highly doubt it is the coolant system, but will check. thank you.
 

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well I'm glad to hear that u r parking the car at least until u find the issue :thumbup: that is the smartest move u can make and yes the aux fan does def scream at high rpm and I mean u can probably hear it from a block away lol so if your fan is not spinning fast enough especially at idle then that could def be a problem I have the 745i and the fan def runs really fast also have u checked the bearings and thermostat on the fan clutch?in case ur not sure its the fan directly connected to the engine not te aux it has a clutch which makes it spin freely from the motor and if that's out it could be another problem it should be able to spin freely with the motor off! If u are not leaking coolant as a matter of fact I would atleast remove the upper radiator hose and thermostat and fill it from there just for peace of mind that u don't have an air bubble in the system somewhere if it all started after ur rad cap was leaking and got the engine hot this can happen I have a bleeder valve on my trans am and my therm went bad so I put a new therm in and filled the system from the coolant reservoir and my car started getting hot almost enough to blow the headgasket and mind u I bled it from the valve but once I filled it from the top of the upper radiator hose all was well just something to try!! also maybe your oil cooler maybe something to check if u were heating up from lack of oil due to a large leak u would know It sooner then later as overhead cam engines will destroy the roller rockers and cam lobes on this 4.4 in a quick hurry which would inturn cause low oil pressure and misfires from the lobes not fully opening the valves. soo make sure ur oil is cooling properly and possibly observe and rule out that your fuel pressure is high enough as running lean is a big cause for overheating and detonation which will also destroy your engine u could have a clogged fuel filter or weak fuel pump check your fuel pressure I know it sounds dumb but if you do some research u will find that running lean can def overheat the engine!! but mostly the fan has to spin at the right rpm in order to cool the coolant in the radiator! so start there first and checking fuel pressure is a cinch if you have the tool otherwise rent it from autozone takes five minutes and just something else to rule out!!:thumbup: with patience and persistence you WILL find the issue my friend
 

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Use INPA and check the "coolant temperature" input to the radiator and the "coolant output temperature" from the radiator. Watch the Analog value 1 screen from the Engine > DME N62 module after you start the car. See if the output temp is lower that the input. The coolant temp will rise to >100C but the coolant output temp will rise but should be much lower.
Let us know what you see
 
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