BMW 335 Quick Coolant Change

[antonmnster]

After changing the oil in my 195,000 mile 335, I figured I'd make use of the two gallons of BMW coolant I had sitting around. Rather than get the car in the air, take off the splash shield, take out the intercooler, drain the radiator, and then think about draining the block, I took a short cut. I just disconnected the return hose that goes back into the reserve bottle. While aiming that hose into a container, I just kept filling the tank as the warm engine idled. Swapped about a gallon and a half in about two minutes. The good news is it was fast and east, and I didn't have to bleed it (which requires a protocol to run the electric water pump). Bad news is I diluted the old coolant instead of really changing it.

The old coolant was in there for 3 years, when I changed the radiator. That job brought me to tears. It looked weirdly dark compared to the new coolant, but otherwise good.

Thought I'd share.

 

[Snagglefoot]

Not a bad idea. Partial replacement, while not a good as full flushing and replacing, still helps to freshen up the corrosion inhibitors. Why not?

 

[FCD]

Partial changes are still good to renew the corrosion inhibitors.

 

[Omahaug]

I don't even bother with full changes any more. Per service manual I know the full system capacity and what I get out of partial is more than enough to dilute whatever old coolant is left. I just do them a little more often than the usual one big, "drain the block and flush everything" style change.

 

[BMWTurboDzl]

Interesting, I would ask more questions but it would be a waste of your time.

 

[maxdustington]

Such a PITA job flushing the normal way. If you're not changing types of coolant or your coolant isn't sludge, this seems like the best way to do it.

It really takes a long time and a lot of distilled water to get that coolant clear. I gave up at the end when two consecutive cycles looked almost identical. If the coolant looks OK and is the correct coolant, I probably will not do that again unless it is a car I never intend to sell.

 

[antonmnster]

I don't mind questions!

On a local BMW facebook page someone asked about routine coolant changes, but a shop owner chimed in that they generally don't need to be done since something in the cooling system usually breaks and dumps the coolant.

 

[maxdustington]

Originally Posted by antonmnster
I don't mind questions!

On a local BMW facebook page someone asked about routine coolant changes, but a shop owner chimed in that they generally don't need to be done since something in the cooling system usually breaks and dumps the coolant.
"Lifetime" coolant = lifetime of the timing belt. No shop that cares about making money is going to put your old coolant back in. Perfect example of not quite lying but certainly being disingenuous to try to get that cost of ownership down on paper.

 

[BMWTurboDzl]

Originally Posted by antonmnster
I don't mind questions!

On a local BMW facebook page someone asked about routine coolant changes, but a shop owner chimed in that they generally don't need to be done since something in the cooling system usually breaks and dumps the coolant.


They're correct. The coolant must be changed when either the OFHG or water pump/thermostat have been replaced. One of those is almost guaranteed to occur within 100k miles.

 

[jrcowboys]

Note you have 195K on your 335. If you have time I would appreciate you out lining what repairs you have done on the car. I have 2012 335 with 70K miles. I have had the following: valve cover gasket, fuel injector stuck open, air mas unit, and catalytic converter. Note: I have just been sucking fluid out of the overflow tank and refilling every couple of months. Doing oil changes every 7500 miles. So far so good. Repairs done at BMW dealer (Austin, TX), seem to do a good job but very expensive.

Aside from repairs car is great, runs like it has 400 HP.

JR

 

[antonmnster]

At this point, what HAVEN'T I done??

I've had the car since 110,000 so much of my list has already been done by the PO.

I've gone through a couple rounds of injectors, valve cover gasket, oil filter housing gasket (at least twice), radiator, oil pan gasket, rear mean seal (it spun in its bore somehow, leaked over a gallon coming back form Chicago), brakes, rotors, shocks, struts, wheel bearings on 3 out of 4 wheels, I keep the serp belt fresh because that's a catastrophic failure, alignments every year, a pair of control arms, a whole bunch of tires, lots of spark plugs and coils, and a pair of HID headlight bulbs. I replaced the DME, but that was a stupid experience because the problem turned out to be a bent spark plug electrode from dropping it. An $800 oops - that's what working in a dark garage can do.

The last owner did the high pressure fuel pump, and the electric water pump/thermostat right before I got it. I'm a little surprised they still work.

Right now the car is very solid. The evaporator is leaking; I'll probably take that on next spring. The bumpers really need to be resprayed due to cross-country winter driving and Chicago parking.

The rear main seal and alignments are the only work I didn't personally do. To upgrade the car to a more modern version of the same model would run around $30K. It's way cheaper just to keep this on on the road!

 

[jrcowboys]

I noticed you didn't mention the turbo or cleaning the intake valves, Is the turbo original and you didn't have to clean the valves?

Thanks for the info.

JR

 

[jim302]

Originally Posted by maxdustington
Such a PITA job flushing the normal way. If you're not changing types of coolant or your coolant isn't sludge, this seems like the best way to do it.

It really takes a long time and a lot of distilled water to get that coolant clear. I gave up at the end when two consecutive cycles looked almost identical. If the coolant looks OK and is the correct coolant, I probably will not do that again unless it is a car I never intend to sell.


It only takes a few drops of coolant to dye the water lightly, so even with repeated drain and fills it is next to impossible to get the water completely clear - especially with darker colored coolant. But if you look at the capacity and measure what you get out, it is relatively easy to determine at what point there's not enough original coolant left to matter.

It is still time consuming to do it this way, so I'm favoring doing drain and fills at half to 3/4 of the OE service interval. As long as you're sticking with the same type of coolant and the system is not contaminated, this is more than enough in my opinion. By doing it a little early, the original coolant still has some good additives left.

 

[antonmnster]

Oh, I cleaned the valves manually last summer. PITA. They were very dirty, but cleaning didn't help that much.

Turbos are original as far as I can tell. Seems like it would be impossible to have originals at almost 200,000 with no wastegate rattle, but who knows. They work great but I'm an easy driver most of the time.