Losing engine coolant

[Jweymiller]

I have a Cummins ISL 400 in a Dutch Star with 60,000 miles.
Runs fine but I loose 1/2 gallon of coolant in about 2,000 miles.
No leaks, never any on the ground. No sign of anti-freeze in the oil.
I am looking for some suggestions where it may be going.

[Dtwallace]

Are you topping off your recovery tank? If so you may be over filling by 1/2 gallon or so.

Sometimes the system will look low in the tank because it draws coolant back into the engine water jackets as it cools down.

If you are looking at you overflow catch bottle when your coach has cooled down, it may appear low but is at it's cold check level.

If you are topping off in this condition, it will blow out the excess out through the over flow onto the road, and you will never see a leak.

Please forgive me if you already know this, I would not try to insult your intelligence. This is a commonly over look occurrence.

Now, a real problem could be your cap ether not seated due to not tighten to the lock, or the cap is bad allowing the same overflow to happen each time you use your coach, not holding proper pressure and blowing your coolant onto the road.

Two: A hose is leaking from a lose clamp just enough to lose a small amount of fluid onto the hot engine. Because the fluid is under pressure, it can push past in very minute amounts and evaporate before it's location is detected.

Lets try a pressure check of your cooling system while it is cold. The engine metal will have contracted, and a leak should appear before your eyes at one of the aforementioned locations.

No Leak found: replace the cap, they are cheap, also check all the hose clamps.

Hot Check: With an assistant starting the first cool, then recheck hot engine, stand at the rear close to the exhaust outlet and watch for a white smoke when the engine is started. Also notice the smell.

A heavy white smoke sometimes indicate an internal leak into the combustion chamber.
A small leak as you described may not degrade the engine performance as the antifreeze will burn in the combustion process along with the fuel.

Ok, I hope this drawn out post will help you find the issue. I'm almost sure it's not a serious problem, but the last check could easily help you identify it on you own.

Good luck and please keep us informed

DTW

[Dutch Star Don]

"Dtwallace".....gave you great information. Remember to use your nose. You may not see a leak, but you can often smell it when warm. Don't forget to check the front of the coach. Those heater hoses run the length of the coach, all the way to the firewall and heater core.

[Jager]

I had this same problem when I first bought my coach. I would lose a quart every 600 miles or so. Everything ran perfect but still loosing coolant. I park it in my garage as well and there was NO SIGN of any leaks anywhere. I crawled around under it and couldn't see a thing either. All at the same time there was no sign of coolant in my oil either.

Took it to a Cummin's certified repair center . . . turned out to be a leak that you could never see. It would only build up enough pressure to leak when the engine was up to temperature and the leak was very small and dripped on something pretty hot . . . so nothing ever made it to the ground. I also have a pretty sensitive nose and I never smelled it either.

Simple fix but finding it . . . that took a little work.

[Jweymiller]

Thanks for all the replies. Lots of good suggestions.

[Ron Postma]

if you have an Aqua Hot heating system check the engine pre-heat loop. They put the wrong clamps on the aqua hot end and it would leak there.

[DAJO]

My loss of coolant was only found by pressure testing the system with compressed air. The small coolant hoses going to the turbo were leaking at the turbo under pressure. Just drove 4,000 miles and no loss now. The leak had me very worried that the egr had an internal leak.

[Jweymiller]

Good idea. I think a pressure test is my next move.

[Jager]

Pressure testing is the only way to go honestly. You need to do that. However be aware that on my coach the radiator cap is NOT a standard size. It required some special size for buses or large trucks. Your average shop won't have the required cap.

[Lug_Nut]

Well, there are other strange events that can result in lost coolant. My Essex experienced a major leak that stopped as soon as the engine started warming.

I was in Frankenmuth Michigan years ago in the winter. I was headed home after a short holiday in the south and stopped for the night. It was very cold that winter night, near 0 F. I had kept the block heater turned on all night as I was in Jelly Bear Park It started fine the next morning. Doing a quick walk around I saw coolant pouring out just behind and forward of the radiator. Now when I say pouring, it was running onto the pavement at about a quart a minute.

Being Sunday, there were not many service stations open, but I hoped to find one fast. Nope! Could not find one. So I stopped in a rest stop just a few miles from the park I had just left. I left the engine running and crawler under to check it out. No leak! Everything was pretty dry too. I travelled the rest of the way home, about 350 miles. It never leaked again. I did, however tighten all the clamps on any lines under there latter that week.

As I learned sometime later, I had experienced a thermal leak. The front heater is suppied with hot glycol via a metal pipe. One to supply the front heater and one for the returning fluid. The cold frigid air has thermally shrunk the metallic pipe and allowed glycol to pass at the hose joint. Once it was warmer, even not real cold, it stopped. Wow! Easy fix!

Hopefully yours is something as simple and cheap.

Peter

[Dtwallace]

Originally Posted by Lug_Nut

Well, there are other strange events that can result in lost coolant. My Essex experienced a major leak that stopped as soon as the engine started warming.

I was in Frankenmuth Michigan years ago in the winter. I was headed home after a short holiday in the south and stopped for the night. It was very cold that winter night, near 0 F. I had kept the block heater turned on all night as I was in Jelly Bear Park It started fine the next morning. Doing a quick walk around I saw coolant pouring out just behind and forward of the radiator. Now when I say pouring, it was running onto the pavement at about a quart a minute.

Being Sunday, there were not many service stations open, but I hoped to find one fast. Nope! Could not find one. So I stopped in a rest stop just a few miles from the park I had just left. I left the engine running and crawler under to check it out. No leak! Everything was pretty dry too. I travelled the rest of the way home, about 350 miles. It never leaked again. I did, however tighten all the clamps on any lines under there latter that week.

As I learned sometime later, I had experienced a thermal leak. The front heater is suppied with hot glycol via a metal pipe. One to supply the front heater and one for the returning fluid. The cold frigid air has thermally shrunk the metallic pipe and allowed glycol to pass at the hose joint. Once it was warmer, even not real cold, it stopped. Wow! Easy fix!

Hopefully yours is something as simple and cheap.

Peter

Lug_Nut,

You would be surprised at how often that happens with Diesel engines, different metals comprising the cooling system expand and contract at different rates.

DTW

[SMertens]

You said you were adding coolant, but was your temperature rising? I agree with getting a pressure check. If you are truly loosing coolant and not seeing any on the ground, might also be a EGR cooler.