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Discussion Starter · #1 ·
Just replaced the radiator and thermostat in my '97 528i.... All went well until I fired it up and went for a test drive around the block. let the car warm up for ten minutes before I took off. Within minutes of driving it nearly went to red line. After getting it home, I rechecked the coolant level and that was fine. However after checking the top and bottom hoses I realized they were both super tight and ready to pop from pressure. I let the engine cool down and rechecked the coolant level, it was a smidge low so I filled it to correct level, let warm back up and went for another test drive, did fine for ten minutes or so and as I was on my last turn before home, red line. Same deal, major pressure in the top and bottom hoses, and when I took the radiator cap off, it gushed fluid. It seems as though there isn't any flow...? Maybe its the water pump or maybe an air bubble in the line? :dunno:Also, on my second test drive the heater worked as normal, when it got hot the cabin heat blew cold air consistently. Stumped here and could use some experienced advice!!!!!!!!!!!!!!!

Rich
 

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...Maybe its the water pump or maybe an air bubble in the line? :dunno:Also, on my second test drive the heater worked as normal, when it got hot the cabin heat blew cold air consistently. Stumped here and could use some experienced advice!!!!!!!!!!!!!!!

Rich
Did you follow one of the DIY procedures here for bleeding your system? Did you have the heater turned on when you bled the system?
 

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Dinggg....what now!
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were there overheating issues earlier that made you changeout the rad n stat?if no then you have not bled the system properly.open both the bleeder screw on the stat housingg and the rad cap and fill,either slowly pouring water in or pressure fill using garden hose till water comes out of both bleeder ports.close the stat housing bleeder screw and continue to fill till water comes out of the rad cap bleeder port.then close bleeder screw and cap.run the engine and watch the temps.

if you have been having overtemps issues previously then perhaps yr problem is with the head or head gaskets........not good....
 

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if you have been having overtemps issues previously then perhaps yr problem is with the head or head gaskets........not good....
True. By all reports here, overheating for any length of time kills the heads on the sixes. When I was shopping for my car, a mechanic told me that the sixes were more prone to head problems than the eights because the head was longer and more apt to warp. Don't know how true that is, but it sounds reasonable.
 

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Also, after reading Bluebee's response to you in the other thread, I have to agree with her that the water pump is a real possibility. Had you replaced it recently, or has it been a while? Aside from the possibility that a faulty water pump may have been causing the problem that you tried to solve by replacing the radiator and thermostat, it would have been a relatively trivial matter to replace the water pump at the same time as the thermostat.
 

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True. By all reports here, overheating for any length of time kills the heads on the sixes. When I was shopping for my car, a mechanic told me that the sixes were more prone to head problems than the eights because the head was longer and more apt to warp. Don't know how true that is, but it sounds reasonable.
Not so much warp as internal stresses are more on the six because it is so long, seems always cracks at cyl 3 or 4, mid-engine.
 

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Give us a better story.

What were the symptoms BEFORE you replaced your rad and thermostat?

BTW, this is the worst thing you can do to your car: a piecemeal approach to the cooling system! You need to do a complete cooling overhaul.
 

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Discussion Starter · #8 ·
Yes originally the car was losing water resulting in no cabin heat and overheating because of the bad radiator. After a compression test I found a sizable leak in the upper drivers side of the radiator. So I figured a simple fix was to replace the radiator and while I was at it, might as well replace the thermostat.... There had been zero overheating issues before I found the leak in the radiator. Good grief, I sure hope it isnt a warped head or bad gasket! When I took it out for a test drive I didnt notice any power issues and I also did check for coolant coming from the exhaust and found nothing.
What is boggling my mind is why are the top and bottom radiator hoses bulging with pressure when the car is at an idle?! Upon my return back home on my second test drive I removed the radiator cap and it gushed nearly a quart of coolant before I recapped it.... If the head is warped and or the gasket is toast, would there be such a great amount of pressure buildup within the coolant system???

Rich
 

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... If the head is warped and or the gasket is toast, would there be such a great amount of pressure buildup within the coolant system???
YES!

Typical gasoline engine produces around 1500-2000 psi range right after the detonation (after the piston leaves the TDC).

Back to your problem, do a leak down test, but unfortunately I think you have a blown head gasket or cracked cyl head.
 

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Dinggg....what now!
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my experience with my previous e34 m20b25,the cylinder head wad cracked at a place where the compression of the pistons also compressed the cooling passage,hence pressurising the cooling system -> bulging and pressurised coolant hoses even after the car has sat overnite.

so....chk,chk and rechk,bleed bleed and rebleed yr coolant.follow cn90's procedure.he has got it spot on.....
 

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YES!

Typical gasoline engine produces around 1500-2000 psi range right after the detonation (after the piston leaves the TDC).

Back to your problem, do a leak down test, but unfortunately I think you have a blown head gasket or cracked cyl head.
Ouch - but makes sense
 

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After a compression test I found a sizable leak in the upper drivers side of the radiator. Rich
Do you mean you "pressurized the cooling system," or you did a "compression test?"

What is boggling my mind is why are the top and bottom radiator hoses bulging with pressure when the car is at an idle?!
Any time there is pressure in the system, it will try to spread itself evenly, which will create pressure in both hoses.Not to be flip, but it boggles my mind that you apparently took the cap off the reservoir while the engine was still hot. You never answered my questions about bleeding the system, by the way.

"Upon my return back home on my second test drive I removed the radiator cap and it gushed nearly a quart of coolant before I recapped it. If the head is warped and or the gasket is toast, would there be such a great amount of pressure buildup within the coolant system???"

Any time the coolant is overheated, it builds up pressure, and if that pressure is suddenly relieved, it will vaporize, expanding rapidly and forcing coolant toward the low pressure (open) area.
 

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Discussion Starter · #13 ·
YES!

Typical gasoline engine produces around 1500-2000 psi range right after the detonation (after the piston leaves the TDC).

Back to your problem, do a leak down test, but unfortunately I think you have a blown head gasket or cracked cyl head.
After reading your reply, it would make sense that a bad head gasket would create such pressure within those hoses. I will add that I DIDN'T follow your exact instructions for refilling the coolant. In fact, I added my first quart and a half directly into the resevour and waited and waited for it to circulate but it wouldnt. So, I went back and reread the instructions and realized I should have been filling it through the thermastat housing hole. Also, the previous owned must have changed the thermastat and used a rediculous amount of sealant. If a piece of that old sealant plugged the 1/16 air hole, could that be the issue? Lastly, I have realized that the electric fan isnt working. Doubtful that the burned out fan is causing the pressure buildup though......:mad:
 

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Discussion Starter · #14 ·
Did you follow one of the DIY procedures here for bleeding your system? Did you have the heater turned on when you bled the system?
I cracked the cap to relieve some of the pressure, hope you weren't thinking I was blindly removing the cap not knowing it was hot and under pressure, lol! To answer your question, no I did not follow his instructions exactly. To answer another question of yours, I pressurized the coolant system, not a compression test.
 

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...Also, the previous owned must have changed the thermastat and used a rediculous amount of sealant. If a piece of that old sealant plugged the 1/16 air hole, could that be the issue?
I don't know all the ins and outs of the BMW cooling system, but I suppose it's possible that plugging the 1/16 inch air hole could create a problem. I just don't think it's likely that excess sealant would get in there.

Also, since you didn't really bleed the system, you apparently didn't turn on your heater either. I think it would be worthwhile to try to bleed your system properly first, to see if that remedies the situation. If it doesn't, then do a leak down test, as cn90 suggested.
 

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I cracked the cap to relieve some of the pressure...
You would have been better served backing out the bleed screw on the reservoir slowly to relieve some pressure and allowing any vapor trapped at the top of the radiator to escape.
 

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Discussion Starter · #17 ·
I don't know all the ins and outs of the BMW cooling system, but I suppose it's possible that plugging the 1/16 inch air hole could create a problem. I just don't think it's likely that excess sealant would get in there.

Also, since you didn't really bleed the system, you apparently didn't turn on your heater either. I think it would be worthwhile to try to bleed your system properly first, to see if that remedies the situation. If it doesn't, then do a leak down test, as cn90 suggested.
You're right, I didn't have the heater blowing. Tomorrow is a new day, so I will start from step one on the system bleed. If that doesn't do it, a leak down test will be next.

Thanks a million for all your help everyone! ;)

Rich
 

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Discussion Starter · #18 ·
Update....

I followed the refill instructions exactly as directed. What I am getting while the engine is running is a steady stream of bubbles flowing out of the coolant reservoir. Its as if someone is blowing into the coolant system with a little red coffee straw...if that helps paint the picture better. I'm not seeing any overheating as it is idling. After a solid 20 minute warm up, I buzzed around the block and didn't see temp rise, however upon returning the hoses were once again tight with pressure. I am getting a rough start up, and am seeing a decent amount of exhaust/condensation from the exhaust pipe. All indications of a warped head/gasket.

Anyone have a reliable link to a top down leak test? This is something I haven't done before and I'd like to get it correct the first time! I priced out a complete gasket set and new head bolts and found a reputable shop to resurface the head, anyone have a reliable link to a head gasket replacement?

BTW, everyone who has replied to my thread has been super helpful, I just wanted to say i appreciate everyones help and advice!
thanks in advance!
Rich
 

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I agree that the symptoms of a rough start up, combined with the steady bubbles, suggests a head gasket problem. 540Alex found a DIY video on You Tube for a leak down tester, and he made one himself, described in his thread about losing compression. A search should bring up his thread, and a search of You Tube for "leak down test" should bring up the video.
 

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After re-reading your post, I wonder. You said you had no overheating after warming it up and driving it around. That doesn't sound like typical blown head gasket behavior. The pressure in both hoses after driving around is normal, I think, since the entire system is under pressure (you have a 2 bar pressure cap). The condensation could simply be from cold ambient temperature. Water vapor is the chief by-product of the combustion process.

I'd take it for a longer (time-wise) test drive, staying close to home, to see if I could provoke overheating. Did you get any computer codes following the rough start up?
 
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