Any advice on stopping a leak here? I replaced the short coolant bypass hose several months ago and seem to have developed a leak at the junction of the housing to the head.

Should I use RTV or some other sealant in addition to the gasket?

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83 300d - 390k

just the gasket will be fine. sealant was only used one place in these engines when they were built. i think that was betwen the block and the upper oil pan.

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-Trevor

OBK #12
1980 300SD 333,XXX miles - Totaled
1986 Mazda RX-7 212,XXX miles - impounded and auctioned off
2005 Jeep Liberty CRD Limited 33,000- SEGR, Provent, Fumoto

Just the gasket, that's what it was designed for.

As 79300sdtd noted, the upper oil pan is the only place on the engine sealer should ever be used.

Permatex makes an RTV specifically for cooling system use. If I were you, I would put a thin coating on both sides of the gasket. Permatex #2 would also be a good choice.

http://www.permatex.com/products/automotive/automotive_gasketing/gasket_makers/Permatex_Water_Pump_Thermostat_RTV_Silicone_Gasket.htm