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Discussion Starter · #1 · (Edited)
Ok, i think i have a leak issue. I just dont where its at. I can drive my car (1999 740i) for about 30 minutes before it get to normal temp (middle of gauge). Then it starts to head towards the red zone. Anyways, i put coolant in the resevoir let it run (with cap on and heat on inside) for 10 minutes then unscrewed bleeder screw. Some antifreeze came out under pressure. Also when the car was running, i saw a medium drip coming from the bottom of the car. Not gushing, but steady for a few seconds and then stopped. I checked the upper hose that connects from the water pump to the radiator, and there was nothing in there (that i could feel), it just kept getting hotter and hotter. I know the engine isnt getting coolant because none is coming back through the upper hose, hence the overheating. Thermostat? Water pump? Hoses?
 

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Overflow reservior tank tempature sensor gauge has a broken tube on the inside of the tank. Fluid will freely come from the bottom where the tempature sensor gauge is I just replaced mine last week with the same issues and it works perfect now.
 

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Very hot engine will thin the oil - pressure drop at idle. 1) Fix cooling problems. 2) Change oil. Is the radiator partially blocked? Is the thermostat opening fully. Is the thermo fan cutting in? Is the fan clutch OK? Is the water pump OK -impeller blades? No need to pressurise system for bleed. The water pump provides sufficient flow to push out any air. Is the theromstat the correct one? Pressure test system for leaks. Debris on outside of radiator core? That should keep you busy for a while.................
 

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Discussion Starter · #8 ·
The radiator isn't clogged because I can put coolant through the reservoir, it goes through the system and comes out of the bleeder screw at the top of the radiator. The fan that sits right behind the radiator definitely works. The water pump i think is in working order, wouldnt it lock up if it was broken? Regardless I think I need to replace the water pump and the thermostat. One of the Indys out here said it could possibly be the valley pan leaking, which I really hope not, being it is a) a pain in the ass to fix on your own and b) expensive if you take it somewhere. Would the water pump still spin and "act" like it's working if the impellers are broken? I just know that I can put in coolant and it doesn't seem to circulate right. Also the upper radiator hose almost always pops off at the connection to the radiator, after the message about "stop engine/check oil pressure" alert comes on.
 

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That sounds like an over pressure caused by boiling problem. Points to partially blocked rad. You note 'it doesn't seem to circulate right' - radiator /water pump / thermostat problem. Impeller blades can corrode away leaving not much more than a spinning disc. no easy way to check it though. The ammount of coolant that comes out through the bleed screw would only be 0.1% of what the pump should move so it is no great guide to overall flow.
 

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Discussion Starter · #10 ·
Thank you for the follow up. I think it points to the water pump/thermostat, because there is seemingly only hot air going through the upper radiator hose, hence the dislocation at the hose-to-radiator connection. I'll replace those two this week and come back with a result post. Thanks again!
 

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Don't forget to use a genuine thermostat - they have two 'layers' of valves on the same stem (usually). When cold, water is force circulated round the block for a fast even warm up. As temp goes up the radiator ports are exposed and cooling begins. Boiling can damage the thermostat and temp senders to the EFI computer and dash gauge. The senders show the wrong resistance at a given temp and 'lie' to the device at the other end.
 

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Ouch! Hope you have a manual, camera and a good tool kit. Do some compression tests first if possible.
 
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