Thread Tools Search this Thread Display Modes
Old 09-25-2018, 10:09 AM   #1
Max Simmons's Avatar
City: Everett, WA
Vessel Model: Ocean Alexander 38'
Join Date: Oct 2007
Posts: 692
Onan Coolant Leak

I have been pulling my hair out trying to find a coolant leak in my 8kw Onan genset. Recently, I pulled the heat exchanger and had it cleaned out at the local radiator shop. Replace a bunch of hoses at re-install, ran it for hours and all was good. Put sound shield back on and proceeded to use as normal for the remainder of the season. On our last trip, I opened it up to check oil and noticed some coolant in the bottom tray. I mopped it up and added some more, fired it up and checked for any obvious leaks, found none. I chalked it up to maybe I filled it too much and the coolant was from expansion. Left it and all was dry. 2 weeks later, was down at the boat and decided it was time to change the impeller, opened the sound shield and there was at least a quart or more of coolant in the tray. So, it's leaking from somewhere while not running. Checked all the hoses, connections, water pump, etc. and nothing.
I'm thinking that I need to pressurize the closed side of the system and check for leaks, just like a radiator in a car. Any suggestions, comments, advice?

Max Simmons is offline   Reply With Quote
Old 09-25-2018, 12:22 PM   #2
Senior Member
NightCrawler's Avatar
City: Beaufort, NC
Vessel Name: Shangri-La
Vessel Model: Grand Banks 42 Classic
Join Date: Feb 2016
Posts: 203
Probably a wrong answer, have the same genset. Thought I was leaking coolant, but no color. The pipe under the rear of the engine that moves sea water had rubbed through on the floor of the case. JB Weld to the rescue.

Possibly water pump? Most have a weep hole that begins leaking when the seals start to go.

Jan & Lee
Lying Beaufort, NC
NightCrawler is offline   Reply With Quote
Old 09-25-2018, 12:39 PM   #3
Lepke's Avatar
City: Between Oregon and Alaska
Vessel Name: Charlie Harper
Vessel Model: Wheeler Shipyard 83'
Join Date: Jun 2016
Posts: 2,328
Yes, Pressurize it. I also vote for the weep hole in the coolant pump. Usually it means the bushing behind the seal is getting worn and the wobble wears the seal.
Lepke is offline   Reply With Quote
Old 09-30-2018, 04:38 PM   #4
Alaskan Sea-Duction's Avatar
City: Inside Passage Summer/Columbia River Winter
Vessel Name: Alaskan Sea-Duction
Vessel Model: 1988 M/Y Camargue YachtFisher
Join Date: Jul 2012
Posts: 7,082
Place some absorbent rag under the genset. run it, then look at the rag and see where on the engine it is leaking.

You do have a recovery tank correct?
Alaskan Sea-Duction is offline   Reply With Quote
Old 09-30-2018, 05:44 PM   #5
TF Site Team
koliver's Avatar
City: Saltspring Island
Vessel Name: Retreat
Vessel Model: C&L 44
Join Date: Nov 2007
Posts: 4,192
Also check the heat exchanger end caps. They can drip some.
Don't let any fluids remain on the floor of the enclosure. If they get blown into the windings of the generator, it can cause a total loss.
You don't want first hand knowledge of this, as I have.
koliver is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

» Trawler Port Captains
Port Captains are TF volunteers who can serve as local guides or assist with local arrangements and information. Search below to locate Port Captains near your destination. To learn more about this program read here: TF Port Captain Program

All times are GMT -5. The time now is 07:42 AM.

Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012