ISC Coolant Leak FYI

[TSM35]

A lesson learned that I hope may help others as I couldn't find anything posted anywhere about this problem.

My 2000 ISC 350 had a coolant leak under the water pump which was diagnosed as a water pump seal failure which made sense since the coolant was leaking just under the tell tale. Two water pumps later and multiple re-installation's of the pumps the leak still existed and was getting worse but only when the engine was hot enough to build pressure (900 miles from home). After significant troubleshooting with multiple shops over 3 days all to no avail I limped it home. Once home I found that an expansion plug (freeze plug) just under the pump was leaking. It's a nightmare to replace because it's half covered by the timing gear cover which is a monumental job to remove. I was able to use a round carbide die grinder to remove enough material from the timing cover to wedge the new plug in and seat it properly. Mind you this sounds easy but has been a 3 month issue with multiple trips to Cummins and Indy truck centers as well as a nightmare 900 mile drive home with 3 and 5 year old girls and an angry wife. Additionally until I actually replaced it I had no idea if I would have to remove the timing gear cover which I was dreading.

The problem is that sediment gets trapped between the timing gear cover and the freeze plug and just sits there corroding the plug until it finally leaks. It's impossible to see with the water pump on and was so covered in road grime it was hard to see even with the pump off. It only leaked under pressure making it doubly hard to find. I only found the problem by poking around with a screwdriver and rag while cleaning coolant and actually poked a hole through it.

I had asked Cummins initially if there was a freeze plug anywhere near there that might be leaking but was told multiple times that there weren't any. Once I was certain a plug existed I had to go to Cummins and show them on the computer as the parts man insisted none existed. Actually there are two and they cost $3 each.

I have lots of photos if anyone is interested. Hope this helps someone in the future as it's been a nightmare for me this summer.

[dons2346]

TSM, I'd be interested in seeing your pix. Please post, thanks

[CountryFit]

thank you for your sharing. i am interested in seeing the photos, too.

[John Jones]

Love to see those photo's, thanks for sharing

[HeapBigEngin]

Very interesting. BTW, what is the mileage on your coach? Also, do you know if the coolant filter has been changed regularly? If not, is it possible IYO that that could have contributed to the crud build up problem?

Thanks....

[H. Miller]

Originally Posted by HeapBigEngin

V do you know if the coolant filter has been changed regularly? If not, is it possible IYO that that could have contributed to the crud build up problem?

Thanks....

As I read it, the "crud" buildup was on the outside of the engine having nothing to do with the water filter..

[hillboy]

pictures would be great. Sounds like getting the new plug in would be a job. How did you get the remainder of the plug out? Part number or page location on the plugs ?Thanks

[KEH]

Thanks for providing helpful information. I too would like to see your pics.

[HeapBigEngin]

Originally Posted by H. Miller

As I read it, the "crud" buildup was on the outside of the engine having nothing to do with the water filter..

My error in interpretation. I've replaced my share of leaking freeze plugs over the years and have yet to see one corrode/leak from elements on the outside. They corrode/leak usually from what's going on in the inside, hence my misdirected suggestion. Unusual for sure....

[TSM35]

Originally Posted by HeapBigEngin

My error in interpretation. I've replaced my share of leaking freeze plugs over the years and have yet to see one corrode/leak from elements on the outside. They corrode/leak usually from what's going on in the inside, hence my misdirected suggestion. Unusual for sure....

I agree, this is the first one I've seen corrode from the outside. The internal side looked like new. I change the coolant filter annually and I always use the Cummins test strips to ensure proper pH. The coach and engine have 78,000 miles on them.

Photos to come.

[TSM35]

Here you go.
The 3rd photo is after I cleaned the crud away from the plug.

The 4th photo is after I poked through the plug and dug out all the corroded rusty metal. I considered tapping it and putting a plug in as instructed by a repair shop. Glad I didn't.

The 5th photo is after the old plug was removed. Notice another freeze plug above the water pump location. It was very solid so I didn't replace it.

The 6th photo shows the new plug installed. If you look closely you can see where I ground the timing gear cover to make room for the plug. There's a metal gasket between the cover and block that gets removed as well. It can be seen in previous photos. It was still a tight fit and had to be angled then tapped in with a hammer and socket but it popped right in. Unfortunate I threw way the package the plug came in so I don't have the part number.

[TSM35]

Originally Posted by hillboy

pictures would be great. Sounds like getting the new plug in would be a job. How did you get the remainder of the plug out? Part number or page location on the plugs ?Thanks

To remove it I hit it on the outside edge with a hammer and socket extension to break it loose then used a slide hammer in the hole to pull it out.

btw... I used Permatex aviation form-a gasket around the plug to seal it. That's what I've used for 30 years on freeze plugs with great success.

[TSM35]

Originally Posted by HeapBigEngin

My error in interpretation. I've replaced my share of leaking freeze plugs over the years and have yet to see one corrode/leak from elements on the outside. They corrode/leak usually from what's going on in the inside, hence my misdirected suggestion. Unusual for sure....

Here's what the inside of the plug looked like after removal vs photo 3 above. I'm going to fill the recessed area with RTV black so it doesn't fill up with road grime again.

[HeapBigEngin]

Thanks for the pictures. That is really an unusual situation. Just when ya' think you've seen or heard just about everything, another surprise comes along. Great job, and thanks again for the pics. Going to look mine over first chance I get.....