BMW Coupes and Sedans 1970-1988 Repair Guide

Freeze Plugs


See Figures 1 and 2

The freeze plugs are the round metal disks pressed into the sides of the engine block. The freeze plugs allow access to the interior of the engine block to clean out the casting sand used during manufacture. A more proper term for freeze plugs would be core plugs. The term freeze plug came from the thought that if the coolant were to freeze and expand, the freeze plugs would be pushed out and prevent the engine block from cracking.

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Fig. Fig. 1: Use a punch and hammer to loosen the freeze plug

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Fig. Fig. 2: Once loose, the freeze plug can be removed from the engine block

During the engine rebuilding process the engine block should be hot tanked or otherwise cleaned of all deposits. Before the block is cleaned, the freeze plugs should be removed allowing a greater access to the interior of the engine block.

To get access to all the freeze plugs, the engine should be removed from the vehicle and the transmission removed. All the covers should be removed from the block. It is possible to reach most of the freeze plugs with the engine still in the vehicle, but installation of the new plugs may be hindered by items in the engine compartment.


  1. With the coolant drained from the block, drive a punch in to the freeze plug. Do not drive the punch in more than necessary or contact may be made with the cylinders.
  3. Pry the freeze plug out of the engine block.
  5. Clean the bore of all deposits.

To install:
  1. Coat the outside of the new freeze plug with Loctite® 270® or equivalent hardening sealer.
  3. Drive the freeze plug into the engine block with the rounded side towards the interior of the block. Drive the plug in so the edge is slightly recessed.

Allow the sealer the proper curing time before subjecting the engine to heat or pressurized coolant.