Therefore when the 8.1L engine was released in 2001 it was determined that there was no achievable way to introduce this new engine with a warm manifold type cooling system. However around the 2000 model year Mercruiser realized that the cost of warranty related to condensation induced engine damage had escalated significantly over the past 8 years and was becoming a real issue. Therefore starting in 1992 with the introduction of teh 502 Mag MPI Mercruiser offered the first of several engines with the cold manifold style cooling system. They determined through this testing that no functional damage resulted that could be attributed to the cold manifolds. Mercruiser performed a significant amount of functional testing with the cold manifold systems and the resulting effect of condensation. Therefore Mercruiser set out to determine if there were functional issues to back up the concerns that the exhaust manifolds could not be allowed to run colder than engine temperature. However in 1992 when Mercruiser introduced the 502 mag EFI motor the intake plenum was so large that it interfered with the standard thermostat housing and therefore prevented them. Up until 1992 Mercruiser had almost always configured their marine cooling systems, both raw water and fresh water cooling systems, such that they included warm manifolds. The driving factor for this was the same reason that always seems to govern manufacturers and their products cost. Should I be observing significant pressure in the cooling system after warm-up / driving? For grins I put a thermometer down into the coolant fill port after driving it awhile, and temp was 190F.Question: Do the Mercruiser Engines equipped with the Dry Joint Style Exhaust AND Closed Cooling systems circulate antifreeze through the exhaust manifolds?Īnswer: Mercruiser has made changes over the years between 1/2 and FULL cooling systems. I pressure tested the cooling system after reinstalling the thermostat and there's no leaks. Strangely, after a 15 minute drive, I was able to remove the radiator cap afterwards and there was little or no pressure in it. I'm pretty sure the thermostat has to be opening because there's no way I could idle or drive that long without the engine seriously overheating if the t-stat wasn't opening. Not sure why the running temp is so high, but I'm beginning to think it might be the coolant temp sensor giving off too high a reading- it's also causing the cooling fans to stay on all the time, since they're triggered at about 204F. It will peak at around 205-210F and stays there no matter how long I idle, or even a long drive. Before, I had shut the engine down at 210F but this time I let it continue to run. Got some air bubbles for a few minutes as temp moved through 180F. Reassembled car, repeat the bleeding process. Pretty much behaving exactly as they're supposed to. Both thermostats opened around the same time- began to open at around 180F, fully open by 195F. I put both in a pot of water with a thermometer, and heated the water to boiling. I went and bought another thermostat just to have on hand and pulled the old one. Could the cool water on that side be preventing the thermostat from opening? Or does it effectively work the same way no matter which side the thermostat is on? Curious if you folks have any ideas or suggestions / things to check. This one has the thermostat after the radiator outlet. I suppose it's not outside the realm of possibility to have gotten a bad thermostat, but I'd like to eliminate all the other possible causes as the thermostat is a bit of a chore to change out.Īll the other engines I remember working on have had the thermostat before the inlet side of the radiator (installed at the upper radiator hose). I'm a bit puzzled, in the past I've had no issues with bleeding air after servicing the cooling system. I see no movement of the coolant through the radiator fill when the engine running at temp. Upper cooling hose is hot, lower cooling hose is cool, as is the bottom half of the radiator. Let it cool down a bit, reinstalled radiator cap and went for a short test drive, temps climbed up past 200F and I stopped the engine before it got to 210F. Let it run till it got to operating temp and cooling fans came on (approx 205*), heater is blowing hot air. Filled up with coolant, and while on a steep incline started up the engine and proceeded to bleed the cooling system by letting it warm up with the radiator cap off. Pressure tested the system after reassembly, holds pressure fine, no leaks. Basically did a cooling system refresh- new coolant, thermostat, several hoses, coolant temp sensor, etc.
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