Inboardman
New member
New member here. I’ve been using this forum for a number of years as a reference and found the posts here very valuable to troubleshooting odds and ends. I have a challenging problem now and after searching and reading many posts on the subject am still struggling to understand what is going on. Hoping you guys can help shed some light on it.
Background:
2006 Crusader Captain’s Choice 5.7 MPI. Just installed a new long-block GM crate engine. Reused most of the dressing including HE. Pressure tested HE (cold) before installing, no leaks. I have about 5-6 hours on the engine in break-in. Runs great, no problems with the engine itself. No overheating happening.
Issue:
The coolant overflows the reservoir cap when I run under load at about 2,800 RPM and above. No bubbles in the reservoir as I can tell, just coolant. This is a pressurized reservoir, not after a pressure cap. When it’s in this state with coolant overflowing I feel the hoses on the FW side and they seem pumped up about what I would expect. Temperature seems normal at 160-170. The strange thing is that when the system cools down I can’t see air getting sucked back in, for the most part the reservoir stays full. So far it has dumped out several pints of coolant into the bilge but the level remains high. I removed the overflow reservoir and pressure tested it and noticed the cap was cracking at about 7psi bleeding off pressure all the way down to 1 psi so I replaced the cap. Retested with the cap and now it cracks closer to 10psi and shuts off at 7 psi. The chamber holds at 7 psi, no leaks that I can tell.
Yesterday I removed the thermostat and ran it and temp stayed at 120F until I went WO for a minute then it came up to 135F and coolant came out the cap shortly after when backing down to 3,000 RPMs. It seemed to do better without the thermostat in terms of leakage out the cap. I used an IR gun and everything on the engine seems to be running about what the gauge says, except the manifolds which are 10 degrees higher. I installed a new 170F Crusader thermostat so that appears to good, I can see it open at 170F.
One thing I found when cleaning up the old reservoir was that the de-gas connection was completely blocked, so I drilled a 1/8” hole through so coolant can flow freely from the top of the filter neck. I drilled through a bunch of rusty crap but couldn’t tell if there was actually something substantial I drilled through, or just some metal crap that was caught in there. I looked to see if there was supposed to be some form of check valve there but can’t find any info on it so presume not. This is the same reservoir used in Volvo trucks and I suppose some Volvo Penta applications. Seems pretty simple.
I haven’t pressure tested the entire FW side of the system yet, that is next. Also, it looks like the coolant may be lighter in color than I would expect, so it’s possible it has been diluted with salt water. I will do a sample of that tonight vs. a fresh AF mix. However, the only way this could be happening is if the breach in the HE only happens when hot. I can’t explain how the fresh side could receive salt water from the HE (perhaps during cooldown) and yet hold enough pressure when at higher RMP’s to dump coolant out of the cap. I was wondering if there is some sort of test I can do to see if there is salt water in the coolant. If I crack the cap after a half hour or so once the engine has stopped it still has some pressure and dribbles out of the cap.
Any ideas you guys have would be much appreciated!
Background:
2006 Crusader Captain’s Choice 5.7 MPI. Just installed a new long-block GM crate engine. Reused most of the dressing including HE. Pressure tested HE (cold) before installing, no leaks. I have about 5-6 hours on the engine in break-in. Runs great, no problems with the engine itself. No overheating happening.
Issue:
The coolant overflows the reservoir cap when I run under load at about 2,800 RPM and above. No bubbles in the reservoir as I can tell, just coolant. This is a pressurized reservoir, not after a pressure cap. When it’s in this state with coolant overflowing I feel the hoses on the FW side and they seem pumped up about what I would expect. Temperature seems normal at 160-170. The strange thing is that when the system cools down I can’t see air getting sucked back in, for the most part the reservoir stays full. So far it has dumped out several pints of coolant into the bilge but the level remains high. I removed the overflow reservoir and pressure tested it and noticed the cap was cracking at about 7psi bleeding off pressure all the way down to 1 psi so I replaced the cap. Retested with the cap and now it cracks closer to 10psi and shuts off at 7 psi. The chamber holds at 7 psi, no leaks that I can tell.
Yesterday I removed the thermostat and ran it and temp stayed at 120F until I went WO for a minute then it came up to 135F and coolant came out the cap shortly after when backing down to 3,000 RPMs. It seemed to do better without the thermostat in terms of leakage out the cap. I used an IR gun and everything on the engine seems to be running about what the gauge says, except the manifolds which are 10 degrees higher. I installed a new 170F Crusader thermostat so that appears to good, I can see it open at 170F.
One thing I found when cleaning up the old reservoir was that the de-gas connection was completely blocked, so I drilled a 1/8” hole through so coolant can flow freely from the top of the filter neck. I drilled through a bunch of rusty crap but couldn’t tell if there was actually something substantial I drilled through, or just some metal crap that was caught in there. I looked to see if there was supposed to be some form of check valve there but can’t find any info on it so presume not. This is the same reservoir used in Volvo trucks and I suppose some Volvo Penta applications. Seems pretty simple.
I haven’t pressure tested the entire FW side of the system yet, that is next. Also, it looks like the coolant may be lighter in color than I would expect, so it’s possible it has been diluted with salt water. I will do a sample of that tonight vs. a fresh AF mix. However, the only way this could be happening is if the breach in the HE only happens when hot. I can’t explain how the fresh side could receive salt water from the HE (perhaps during cooldown) and yet hold enough pressure when at higher RMP’s to dump coolant out of the cap. I was wondering if there is some sort of test I can do to see if there is salt water in the coolant. If I crack the cap after a half hour or so once the engine has stopped it still has some pressure and dribbles out of the cap.
Any ideas you guys have would be much appreciated!
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