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2004 325i 5sp
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Discussion Starter #1
I just bought my 325i and when i plugged in my scan tool while driving I noticed that my engine was at 99C and my radiator was at 27C. I tried to bleed the system with some distilled water just to see if that was the issue but I don't believe that it is. The radiator stayed stone cold the whole time so it could be a thermostat, water pump, or both. When I turned on the heat, the engine temp would drop according to my app but it wouldn't drop much. Should I just buy a water pump and thermostat and get at it?
Thanks,
Daniel
Edit: There is no warning light at all, the engine temp needle is slightly to the right of center but not by much
 

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2004 325i automagic
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Its a better idea to replace the entire cooling system at this age and mileage, but you should also check whether there is a blockage problem in case a previous owner used a leak sealant of some kind that has plugged things up. With a cold engine, start the car and open the expansion tank cap and check for a stream of coolant bypassing the thermostat splashing around. A lack of return flow could indicate a bad water pump not moving coolant or possibly a blockage.

Another thing to check is whether the upper rad hose gets quickly pressurized during the first couple minutes or so before the engine has a chance to warm up at all.

At a minimum replace the expansion tank (modine or bmw) as well, since it is under full system pressure made of plastic and likes to split at the seam; along with the water pump (Saleri or bmw), thermostat (Whaler, Behr or bmw), both rad hoses (Rein or bmw), and the radiator (Nissens or bmw). The cooling system is a weak point of these cars and once one thing starts to fail, others are likely to follow so its good to just open it up once and be done with it.

I also would not drive this car too much or too far until I had the cooling system sorted because an overheat can be catastrophic to these engines.

Btw, if the temp gauge needle is moving to the right, it is a little surprising that the engine coolant temp is not reading above 115C, since the temp guage from the factory is buffered to read 12 o'clock from 75C to 115C. However, it is possible a previous owner reprogrammed the temp gauge to something more reasonable like 90 to 100C at 12 o'clock, which is a common modification.
 

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2004 325i 5sp
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Discussion Starter #3
I'm going to get my coolant system pressure tested tomorrow to see if my radiator is still good, and then order parts accordingly. FCP has bolts in the kit, but aren't the bolts on the car still good? I'm at a minimum going to get a coolant expansion tank, water pump, and thermostat. I might buy hoses if they're in bad condition but I think it's just the water pump. I will figure it out tomorrow though
 

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2004 325i 5sp
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Discussion Starter #5
The water pump is not that expensive and very easy to replace on these cars.
I'm going to order a water pump, it's just a question of what else I get done at the same time
 

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2004 325i automagic
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I'm going to get my coolant system pressure tested tomorrow to see if my radiator is still good, and then order parts accordingly. FCP has bolts in the kit, but aren't the bolts on the car still good? I'm at a minimum going to get a coolant expansion tank, water pump, and thermostat. I might buy hoses if they're in bad condition but I think it's just the water pump. I will figure it out tomorrow though
Try assembling your own 'kit' ... the aftermarket brands mentioned above all have a good reputation and are widely used here for those respective parts.

As for whether you need bolts or a water pump pulley, maybe if the old ones are corroded but likely not. Take the electric fan out and look. Good time to remove the accessory belt and inspect everything up front for leaks and what not. Spin test all the pulleys as well for noise, looseness and grittiness and replace as needed. Check the serpentine & a/c belts as well. You could also rent for a free a coolant system pressure test kit from AutoZone (they fully refund your credit card when you return the kit) and pressure test it yourself.

The point isn't so much whether the radiator is good today or not, as it is whether it might need to be replaced soon anyways ... same idea with the rad hoses (which have o-rings in the connections that can leak). If things are original you really should replace on your own schedule. Either way your car, your call.
 

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Leverthis is on the money when he states -
“At a minimum replace the expansion tank (modine or bmw) as well, since it is under full system pressure made of plastic and likes to split at the seam; along with the water pump (Saleri or bmw), thermostat (Whaler, Behr or bmw), both rad hoses (Rein or bmw), and the radiator (Nissens or bmw). The cooling system is a weak point of these cars and once one thing starts to fail, others are likely to follow so its good to just open it up once and be done with it”.
Don’t use anything else than a modine (original manufacturer of the bmw part) expansion tank - not expensive at fcpeuro.
You guys in the US are so lucky having them as a source for your parts, especially the return policy, if you haven’t checked it out
 

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I would replace the thermostat (Wahler) first. It's the easiest. I had the same problem. 99C before and 94C after replacement. Then if the radiator remains cool it could be the water pump or clogged radiator.
 

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If you're going to keep the car, might as well do hoses and prob rad. If you have no service history, assume the worst - that its all original. There are currently half a dozen current discussions on the same theme.
 

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2004 325i 5sp
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Discussion Starter #12
I just found out that my car has a nissin rad mfd in late 2019! I'm gonna pull the belts and see if I can find any dates on anything else
 
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