1998 400 SD Cooling Question

[hd2002hd]

So, I’ve lost a hose on the seawater pump before and I know the engine temp rises quickly. So my question is, if you lose coolant out of the internal cooling system will the engine temp rise quickly as well. I lost coolant in the bulge and found a leaking cap On the internal cooling system. The reservoir was low but not empty and there was no change in engine temp. Just curious. I would assume the answer is yes but wanted some experienced opinions.

 

[Sublimetime]

It depends how fast you lose the coolant (how big is the leak, burst hose or loose clamp?) and how fast is the motor spinning, (faster rpm usually means more heat and faster buildup of heat). So if it is a small coolant leak you might not see a gauge temp difference until a lot of coolant has left the motor.

 

[hd2002hd]

Thanks, so eventually the temp will rise most likely?

 

[Espos4]

Thanks, so eventually the temp will rise most likely?

It really shouldn’t rise at all, because you’ve discovered an issue ,you’ll repair it (or have the mechanic do it) then be back out boating!

 

[hd2002hd]

Well, my concern was having it get low (leak gets worse) under way. It was small leak, but depending on cause it might have gotten worse. Was wondering g if a rise in temp would be a first indication. There was really nothing I could see visibly (at least initially) except a little coolant in the bilge area. Further investigation led me to more coolant under the engine but only around the drain into the forward bilge and a few drops running toward the aft bilge. I ran the engine until the thermostat opened and the. Shut it down to go look more. All hoses and the pump looked good. As I was setting aft of the engine looking everything over, out of the corner of my eye I say a drip hit the separation piece between the engine side and bilge side. As I looked above I saw some very faint “wet” areas. I traced it up and found that it appeared to be coming from the pressure cap on the reservoir. After I removed the cap it was wet all the way around. I replaced the cap, topped off the coolant and went for a test run. All went well. After it cooled down I checked the coolant and it was at normal level. Since then I have ran about 30 miles on each of 2 days. The first day was slow run all the way just enjoying the scenery. The 2nd day I ran my normal cruise speed of about 3400 rpm’s. Level held both times so I’m calling this a win.

 

[hd2002hd]

The starboard engine (7.4) seems to be leaking a small amount of coolant. Maybe a cup or so after a 1-2 hour run. I assume it is the starboard because the plastic coolant reservoir was low at one point. I thought I discovered a leak around the pressure cap on the aft metal coolant reservoir so I. Hanged it out. However, I still have a leak. What I find after a run is a small amount of coolant in the very center between the engines and between and aft on the plastic reservoirs. I have also noted the starboard plastic reservoir is set on top of the cap. I look over the pump, hoses, etc. and find nothing wet. Nothing wet on the motor, it always a little coolant sateen the engines. Any ideas or suggestions for further troubleshooting to locate this issue?