3888/twin 351 gas - coolant leak/how to diagnose heat exchanger?-gctid818483

[Guest]

Coolant expansion reservoir on the starboard motor was empty a week ago. I refilled it and it went another week of steady 4-6 hr/day cruising before it went dry, but it does seem to be using coolant significantly more than before (we've been cruising at this pace since March).

I have white absorbent pads under the motors and don't see any signs of visible leakage

I've checked the transmission oil dipstick and the oil seems clean (I did an oil change 3 weeks ago). No obvious signs of "milkyness" or smell of coolant.

I have noticed the exhaust on that side has a faint white smoke look more than the port side

I'm thinking maybe the heat exchanger is leaking and the coolant is being blown out the exhaust risers?

Any support or other ideas?

Any idea how to diagnose this other than taking it off and pressure testing/fixing/replacing?

How hard are these to find?

Thanks

[Pcpete]

I'm sorry to tell you that it's time for a pressure test. You can rent a test kit from most of the auto supply chains. I would remove the end caps from the heat exchanger, have a mirror and a flashlight ready. I did emergency repairs on a set (twin engines) that were failing while on vacation by identifying the tube, cleaning it up a bit then plugging it off with marinetex. Plugging one or two tubes off is usually not an issue but it does mean it's time to go shopping for a replacement.

[Guest]

so with the "symptoms"/observations reported, is there any other reason to think it's not the heat exchanger?

I've found replacment parts at manifold warehouse in vancouver and waiting on a reply from Orca Marine in seattle.

Thanks!!!

[Guest]

I had a coolant leak on my port engine a year ago...couldn't spot where it was coming from. Turned out it was the hose from the port heat exchanger to the water heater...replaced that, hasn't lost of drop since then. (These are the Hino diesels, but same conceptual problem.) Do you have a cabin heater that's attached to the starboard heat exchanger, if so check those hoses.

Harbor Freight sells a radiator pressure test kit that has a bunch of different radiator cap sizes...one fits the Hino heat exchangers, and I'd imagine one will fit your heat exchangers. If I recall, it's about $150 (less than the cost for a couple hours of mechanic time)...grab one of those, pump it up to a few PSI with the engines off, and see if you can find liquid squirting or dripping from anywhere. https://www.harborfreight.com/radiat...kit-63862.html

HTH,

Dave

[Guest]

Thanks!!!

Checked and don't have any other hose/connections.

Unfortunately we're cruising in the wilds of the Rideau in Ontario. Hoping to limp in to Kingston, Ont on the port motor (just using the starboard for locking/docking) in a couple days.

Following up on pressure testing and replacement heat exchangers.

Thanks!!!!

[Pcpete]

You can rig a tester for the heat exchanger using a hose T, a garden hose end and some radiator hose. Connect the T in the middle of the radiator hose and the other ends to the closed cooling side of the heat exchanger. Then the open end of the T to the garden hose segment. Connect the hose end to a spigot and turn it on slowly. If it leaks, you'll know it right away. Then you can plug it and be on your way.

[Guest]

another great idea!

Thanks

latest is that I've found a place Manifold Warehouse on the west coast that can get a replacement to the tune of $900 plus expedited shipping in a week. Also found the next marina down the Rideau that is ready to do a "proper" pressure test tomorrow. We'll open the ends of the heat exchanger so we can also see the leak, if it is.

Then, moving slow on one motor and arranging for the next place to get the new unit shipped (also assuming that that's the problem).

Thanks again for all the help and good ideas.

[builderdude]

Be careful pressurizing your cooling system from a hose bib, the closed system runs at about 14 psi and a max of 20 psi for testing only. Hose bib pressure will usually be at least double that, up to 50 psi where I live.

[Guest]

yup another good point to consider. We're planning on doing a pressure test tomorrow when we get to a bigger marina and will definitely be watching that.

[iceclimber]

Pull the exchanger, take it to a radiator shop. Those gents tend to be passionate on the subject and will tell you if your checkbook is going to survive.

Don't ask me how I know this.

[Pcpete]

Yes, any time I did the hose bib test it was with the heat exchanger out of the boat and the end caps off. It never took more than a trickle to find the bad tube. I usually had my oldest so (10 at the time) turning on the hose and I had I'd double kinked to control how much got to the exchanger. They were 3" mercruiser 470's and not the best of anything in my experience. Anytime a guy has to have a 4 x 4 with eye bolts mounted for turnbuckles to lift the front of the engine always aboard be able to finish a two week vacation.....one finally committed suicide, ruining another vacation, whereupon I stripped the engine room and installed a pair of 4.3 kits. End of issues.

[Guest]

So we got to a marina and did the pressure test hooking the pump/gauge to the "radiator" fill cap on the motor. Pumped and tested to 10 psi and held steady. Pumped to 15 psi and still no loss.

Glad I didn't jump the gun and preorder the heat exchanger.

Now I'm flummoxed.

Per my first email, still no visible signs of any external leakage at hoses, water pump, heat exchanger. White pads on engine room floor show no drips. No sign of "Milky ness" in transmission oil. No white smoke in exhaust.

Heat exchanger vendor also offered up sometimes leakage occurs at the SS gasket between exhaust riser and 90 fitting, but mine are one piece.

Bought a bottle of the standard car radiator stop leak and gonna continue to watch coolant levels, but at a loss to explain this one.

??????????

[GearGuts]

I have the same boat same engines, yeah the coolant goes somewhere..... Only a tiny amount once in a while, I havn't been able to figure it out and my system holds 15 psi steady all day long. I would continue to monitor the coolant but I would not add a clogging agent to the system just yet.

[Sportscar]

Do NOT use any type of sealer in your cooling system or you will be dealing with a lot more trouble than a leak.

[Pcpete]

You probably have a leak that opens at some temperature and conditions. These can drive anybody nuts. I suggest keeping a log of how you accelerated and time at given rpms. You probably will not see any difference on your gauges, but a pattern may develop. It can be any number of things. There is a product for checking exhaust gasses in the coolant. This could help because where there is a failure it's often a two way street, as it were. The kit is about $40 and is good for gas and diesels. I'd give you the name, but my youngest son and wife have the boat right now in the San Jaun Islands. It's a fairly new product so I don't know that it's gotten to the wilds of Ontario.

NO sealing goop!