Coolant Loss

[Steve]

Gentlemen,

We have a single 2008 Cummins QSB 5.9 425hp on a Back Cove 33. It was serviced in May 2017 (740 hours) which included coolant replacement and heat exchanger removal/servicing. After about 40 hours, I noticed the coolant level had gone down around 2 inches in the reservoir. I figured it was burping after the coolant/heat exchanger replacement so I added coolant to the reservoir. I marked it to monitor and it is continuing to go down. All measurements were done 24 hours after use. No weeping or signs of leaks anywhere. The bilge is bone dry. The coolant level at the cap checks full every time.

Is it possibly still burping? Other than having the system pressure tested tomorrow, is there anything else I should be checking?

Thank You,
Steve

Topic

[Steve]

You’re right re: the heat exchanger/coolant…same with our QSB. My typing was in gear but my mind was in neutral…sorry

Anyhow If I remember right, I’d guess it took us about 5 trips out about 2-3 hours each time before it settled. I just added to the expansion tank after the engine cooled. It was always full at the engine cap. Haven’t touched it since.

Steve

[Andre Huizing]

Thanks

Thanks for your prompt response Steve. Glad to hear it all went well in the end. On our engine the only cooler where coolant is present is the Heat Exchanger, all other coolers are in the raw water circuit. Do you have an idea after how many engine hours your engine stopped dropping coolant level?
Cheers, André

[Steve]

Andre
It took a few coolant additions, but the level settled and has been fine ever since. At first I had visions of leaking coolers or heat exchanger (even though they had all just been removed and serviced). In the end it looks like it simply took a few uses (and additions) to replenish the coolant completely. The advise I recieved here was accurate…..closely monitor it but be patient just a bit more and see if it settles down. In my case it did just that. Good luck sir.
Steve

[Andre Huizing]

Was this solved in the end?

Hi Steve,
I’m new to this forum so don’t know if it’s any use trying to revive this post. I have exactly the same issue on my QSC8.3 500hp. replaced the coolant this winter. Been cruising now for around 40 engine hours. At first I suspected the “burping” but it continues to loose around 1 quart every 10 hours. Everything bone dry, I shut off the water heater circuit, no visible smoke from exhaust. When I run the engine the level in the expansion tank is hardly going up, when the engine cools down it sucks in a small amount from expansion tank through the pressure cap. Hence, I’m very curious for possible causes of this problem.

Thanks, André

[Steve]

Copy that. I’ll keep a close eye on it.
Thank You Gents,
Steve

[Rob Schepis]

Yup. Be sure to clean everything 100% and be diligent in your checks in case something is weeping when hot like Joe mentioned. Don’t forget to check around any external equipment such as a water heater, if so equipped…

[Tony Athens]

That’s what I’d do..

Tony

[Steve]

The pressure test was completed today and it held at 15 PSI with no drop at all. What’s next? Top it off again and continue to monitor?

[Joe Monaco]

It could be going out the exhaust but I don’t think it is. I had the same situation with my CATs. Had everything serviced and then noticed I needed to keep add a small amount of coolant to both expansion bottles after running 10 hours or so. This went on for a few months then it stopped. I’d keep runnng the boat and see if it stops on its own. Pressure tests will show a leaking hose but without being at operating temp hard to check anything else. As I said I’d bet alls well with your motor just need to add coolant a few more times.

[Steve]

Thanks much for the prompt reply.

Yes the belt guard seems to be holding up fine. It’s mounted on the upper right (if you’re looking at the front of the engine). Seems to be no issues there.

Roger That re: pressure test. It’s scheduled for tomorrow and I’ll post the results. I’d be shocked if it checked OK because if it’s not burping then where could the coolant possibly be going…..

[Rob Schepis]

A couple runs to thermostat-opening-temperature should be all that is needed to burp the coolant and stabilize the level. Continue with the pressure and then post a follow-up here. That plastic belt guard is holding up okay with the recovery bottle mounted on it?

[Author]

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