Good evening,
I have a 2001 Crusader 5.7L TBI. Motor has a closed cooling system cooled by a raw water pump/heat exchanger. I have been working on the engine using a garden hose, however, it overheats when we tried to take the boat out on a fresh water lake.
I bought it used, history reported to have low hours for what it's worth. The motor overheats only at idle (approx 650 rpm factory set). If I bump it up just a bit to 800+ rpm the motor cools right down to 160-170 on the gauge. To date I have chased the problem by doing the following:
- Rebuilding the raw water pump. New cam, new impeller, new seal. It does not leak and the bearing appear to be fine when tested by feel. Neither the inside of the pump nor the cover are worn.
- Flushing the engine and raw water circuit entirely. I've back-flushed all areas of the motor and cooling system that I am aware of. I am able to put a full-power garden hose into the the elbows w/o any back flow, the same is true for the exhaust manifolds. The heat exchanger tubes are clear. The U-cooler is clear. I pulled the drain plugs on the block and flushed the engine completely with fresh water. By putting water into the hose directly at the u-cooler I get full, clear flow at both elbows.
- I changed out all of the closed system cooling hoses. The original ones did have a "crunch" to the them and I did flush a lot of grit out of them when I flushed it.
- Installed a new water pump.
- Checked the thermostat and it is operating properly. I also tried it w/o it installed. It's a 170 degree thermostat.
- Completely drained the closed system and flushed it as well. Filled the system with new coolant.
- Bought a Lisle spill-free coolant "burping" funnel and have removed all of the air from the system as as far as I can tell. Although the engine still appears to need two or three quarts approximately of coolant to meet the 23 qts listed in the manual.
- Replaced the heat exchanger cap.
During operation- even when the temp is rising/hot, the exhaust elbows are cool to the touch as are all of the raw water hoses.
*The one issue I do seem to have is that the exhaust manifolds are hot. Should they be cool to the touch as the elbows are? If so, is it possible they need to be replaced even if I can flush water through them without any seeming obstruction?
Would a faulty temp gauge read like this only at idle? This is the one thing I have not changed out yet.
I did check the engine over with a IR temp gun and found no hot spots except for the exhaust manifold, however, I don't think they matched the 200 and rising temp. I always shut it down when it hits 200 degrees. I will double-check this tomorrow and report my findings.
I'm at a loss and would be grateful for any advice.
Thanks,
Christian
I have a 2001 Crusader 5.7L TBI. Motor has a closed cooling system cooled by a raw water pump/heat exchanger. I have been working on the engine using a garden hose, however, it overheats when we tried to take the boat out on a fresh water lake.
I bought it used, history reported to have low hours for what it's worth. The motor overheats only at idle (approx 650 rpm factory set). If I bump it up just a bit to 800+ rpm the motor cools right down to 160-170 on the gauge. To date I have chased the problem by doing the following:
- Rebuilding the raw water pump. New cam, new impeller, new seal. It does not leak and the bearing appear to be fine when tested by feel. Neither the inside of the pump nor the cover are worn.
- Flushing the engine and raw water circuit entirely. I've back-flushed all areas of the motor and cooling system that I am aware of. I am able to put a full-power garden hose into the the elbows w/o any back flow, the same is true for the exhaust manifolds. The heat exchanger tubes are clear. The U-cooler is clear. I pulled the drain plugs on the block and flushed the engine completely with fresh water. By putting water into the hose directly at the u-cooler I get full, clear flow at both elbows.
- I changed out all of the closed system cooling hoses. The original ones did have a "crunch" to the them and I did flush a lot of grit out of them when I flushed it.
- Installed a new water pump.
- Checked the thermostat and it is operating properly. I also tried it w/o it installed. It's a 170 degree thermostat.
- Completely drained the closed system and flushed it as well. Filled the system with new coolant.
- Bought a Lisle spill-free coolant "burping" funnel and have removed all of the air from the system as as far as I can tell. Although the engine still appears to need two or three quarts approximately of coolant to meet the 23 qts listed in the manual.
- Replaced the heat exchanger cap.
During operation- even when the temp is rising/hot, the exhaust elbows are cool to the touch as are all of the raw water hoses.
*The one issue I do seem to have is that the exhaust manifolds are hot. Should they be cool to the touch as the elbows are? If so, is it possible they need to be replaced even if I can flush water through them without any seeming obstruction?
Would a faulty temp gauge read like this only at idle? This is the one thing I have not changed out yet.
I did check the engine over with a IR temp gun and found no hot spots except for the exhaust manifold, however, I don't think they matched the 200 and rising temp. I always shut it down when it hits 200 degrees. I will double-check this tomorrow and report my findings.
I'm at a loss and would be grateful for any advice.
Thanks,
Christian