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Small Coolant Leak - Big Repair!

3K views 9 replies 4 participants last post by  mjrgroup 
#1 ·
2005 L322. Spotted minor coolant leak on drip pan this week. Attempted to determine origin. Suspected valley pan seal as I found drips on starter. Had indy pressurize to check and found freeze plug on back of passenger side cylinder head bubbling. [emoji22] After conferring with BMW friends, determined dropping xmsn to gain access from below to be best bet for replacing freeze plug without having to open the can of worms associated with pulling the head. At this point, trying to determine the best course of action. $2 part. Best way to replace. Even talking to very experienced BMW guy, never have seen this in an M62 engine. Anyone have any experience with this?

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#2 ·
Couple of things to consider.

First, the pressure in the cooling system is determined exclusively by the coolant expansion tank cap, which has a relief pressure of 2.0 bar (29 psi). One very inexpensive approach you could take it to simply reduce the cooling system pressure to 1.2 bar (17 psi) with a different cap. I did this on Rover 1, which has a very leaky center valley pan (I haven't had time to replace it yet), and the leak slowed significantly to the point where it virtually stopped.

Second, IIRC there are two "freeze plugs" on the M62TU, one of which is behind the metal coolant plate on the back of the engine, which, as you said, requires dropping the transmission.

If I were you, I would immediately buy the German Auto Solutions 1.2 bar coolant cap (I'm already running this on both my Rovers in addition to my BMW 8 series) and install it. Then reassess the severity of your coolant leak.

If you do need to drop the transmission, by all means, replace the rear main seal, freeze plug, gasket for the coolant plate, and replace the coolant crossover pipe gaskets as well.

While you're back there, do the PCV valve, cyclonic oil separator, and associated hoses (2)
 
#5 ·
If I understand you correctly, I would strongly advise against anyone using pour-in sealant products. Sealant mixed-in with coolant is the worst idea as it will gum up your coolant channels or any place else it wants. It doesn't know where the leaks are just the best place to settle in. If I was considering buying a vehicle and suspected that a previous owner of a car used the stuff, I would run.

IMHO, these cars deserve to be fixed right, change the gasket or seal. Don't cheap out and cut corners, it's a recipe for disaster.
 
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#7 ·
NOTE the reason for the higher pressure cap is because the coolant temp runs at an elevated temp compared to older vehicles.
210F is the temp used on the M62
older systems ran at 180F

The higher temp is to produce the best fuel economy.
That said when adding a lower pressure cap to the cooling system,
you should consider modifying the M62 thermostat to the M60 diesel version .
This removes the electric portion,
NOTE The electric portion was added to reduce the amount of cooling supplied unless more was needed due to engine load.
so the cooling system will operate at 210F, withy the restriction then under load it will be opened to fully open thus increasing the cooling available.
Sometimes the elex portion of the T stat fails and then the truck will run hot when the external temp load reaches its delta point.

NOTE the M60 T stat will run at 180 F thus the trans and power steering systems will last longer due to being subject to less heat.

That said the heater will also provide less heat from the original selections,
simply turning up the dial on the temp selector will make the interior warmer
 
#9 ·
Truck back in service. New freeze plug installed after dropping the transmission for access. Saved a ton by doing it this way vs. pulling the head and all that routinely results from doing so. Rear main seal was leaking, so the added expense was relatively minimal as access was no issue.

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#10 ·
Excellent. Kudos on getting it taken care of and for follow-up on this thread...a new rear main seal will you good peace of mind.
 
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