The m42 in my e30 has a chronic coolant leak at the nipple port on the cylinder head, just above the head gasket and below the intake manifolds. When I got the car, the port was connected to the intake heater plate by hose with P/N 1153172846. Leak first started sometime after I did the MUTI procedure, when I capped the port with a 1/2-in diameter bypass cap (Dorman Help! brand), which I tightened with a hose clamp. 3/8-in cap seems too small. The head port doesn’t appear damaged. Capping the head port seems straightforward, but I must be doing something stupid. Leak get worse with time, until I adjust or replace the hose clamp and bypass cap every few months. I’ve tried the following things, and yet coolant always leaks from the head port:
(1) tightened hose clamp
(2) replaced bypass cap and hose clamp
(3) replaced bypass cap, and tried different levels of tightening on the hose clamp.
(4) connected head port to plastic water pipe with an M44 water hose, P/N 11531247398.
Is there a fine line between under tightening and over tightening the hose clamp at this spot? Could engine rattle loosen the bypass cap over time? Is there an option other than a bypass cap to seal this nipple port?
(1) tightened hose clamp
(2) replaced bypass cap and hose clamp
(3) replaced bypass cap, and tried different levels of tightening on the hose clamp.
(4) connected head port to plastic water pipe with an M44 water hose, P/N 11531247398.
Is there a fine line between under tightening and over tightening the hose clamp at this spot? Could engine rattle loosen the bypass cap over time? Is there an option other than a bypass cap to seal this nipple port?
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