daviddunivan
Contributing Member
"i have a 3.7 mercruiser, clos
"i have a 3.7 mercruiser, closed cooling system. motor is rebuilt and head rebuilt and trued up, etc. i was having trouble keeping coolant in cause it was blowing the riser gasket's but i finally got one to seal up good. so then it still had alot of pressure in the cooling system and was still pushing coolant out of the overflow tank, and would slowly push all of it out of the engine. so i took the thermostat out thinking it was stuck. went to the lake without a t'stat in it and still, ton's of pressure in the cooling system, only ran two small circle's around the landing area and it had pushed all the coolant out of the cap, thru a small hose to the overflow and out of the overflow tank. what is causing this pressure, could it be a head gasket??? but no coolant in the oil, and good oil pressure. i will check the compression tonight and try to post back soon, would a head gasket cause this or a cracked head??? also how do you pressure test the cooling system and how do you do a leak down test on the cylinder's i have a compression tester but don't know how it would do the leak down test>? any help is great and hope to get it fixed soon. thanks"
"i have a 3.7 mercruiser, closed cooling system. motor is rebuilt and head rebuilt and trued up, etc. i was having trouble keeping coolant in cause it was blowing the riser gasket's but i finally got one to seal up good. so then it still had alot of pressure in the cooling system and was still pushing coolant out of the overflow tank, and would slowly push all of it out of the engine. so i took the thermostat out thinking it was stuck. went to the lake without a t'stat in it and still, ton's of pressure in the cooling system, only ran two small circle's around the landing area and it had pushed all the coolant out of the cap, thru a small hose to the overflow and out of the overflow tank. what is causing this pressure, could it be a head gasket??? but no coolant in the oil, and good oil pressure. i will check the compression tonight and try to post back soon, would a head gasket cause this or a cracked head??? also how do you pressure test the cooling system and how do you do a leak down test on the cylinder's i have a compression tester but don't know how it would do the leak down test>? any help is great and hope to get it fixed soon. thanks"