Yanmar heat exchanger inspection

[CrispyCringle]

I have a Yanmar 4JH2 series motor and I seems like a smaller that’s normal amount of water is coming out of the exhaust. I’ve checked the strainer and the sea water pump. I’d like to look inside the heat exchanger, but I have never done it and have a few questions.

-Do I need to drain both the fresh water and the sea water from the exchanger before I take the end covers off?

-Do I need to pull the exchanger tubes assembly out, or can I just run a cleaning brush through it?

-Any thing else I should be looking at?

Thanks!

[SY Harmony]

Drain both cooling systems.
The holes in the heat exchanger are about 1/4” dia. The best way to clean it is to pull it and have it rodded at a radiator shop. You’ll want to new ori g to reseal the ends. Also pay attention to the orientation of the core on removal.
It’s possible you have impeller bits in the inlet end as well as build up.

[JimsCAL]

Could also be blockage in the exhaust elbow.

[Tin Tin]

Before doing all that you could run barnacle buster through the raw water system that will likely remove a lot of calcium build up in the heat exchanger. Plenty of videos on you tube for how to do this. for example only

https://www.youtube.com/watch?v=u4bGiv2MD74

[Russ]

Pulling the exchanger off my 110 turbo is hard and complicated. I regularly use Barnacle Buster'
Beware Yanmar recommends ONLY Barnacle Buster as it is an aluminum block. Muriatic acid will kill it.
I run it through the engine with a bucket of BB diluted and a small pond-type pump for about 2-3 hours and then rinse it with clean water the same way.
I had the occasion to clean it before the mechanic replaced all my seals and got to look at my cleaning job the exchanger was PRISTINE. Don't waste your money on taking it off (it isn't simple)
On my prior Isuzu, the end cap for the heat exchanger was a simple unbolt deal and i used brass or wood dowles but the BB is much to be pe-referred,

[CrispyCringle]

Thanks for all the suggestions so far. Ill probably get to it next weekend. Ill post how it goes.

[GreenWave]

I am about to take on this same task on my 4jH3-TE... as for how hard it is - well that depends on your configuration. There are two bolts on each end to come out. On the front you likely will need to take of or move the Alternator and the hose that feeds the front. I plan to have new gaskets and that one hose ready for replacement. Oh and soak the bolts a bit with PB blaster for a day or two before you take them off.


You just need to pull the cylinder shaped tube part out - don't need to remove the whole assembly, which would be much more difficult.

[CrispyCringle]

Originally Posted by GreenWave

I am about to take on this same task on my 4jH3-TE... as for how hard it is - well that depends on your configuration. There are two bolts on each end to come out. On the front you likely will need to take of or move the Alternator and the hose that feeds the front. I plan to have new gaskets and that one hose ready for replacement. Oh and soak the bolts a bit with PB blaster for a day or two before you take them off.


You just need to pull the cylinder shaped tube part out - don't need to remove the whole assembly, which would be much more difficult.

Thanks. Yes that’s what I think I’m going to do. I have new end gaskets on order. Looks like pretty decent access. The worst access looks to be the drain cocks for the coolant and sea water. Both difficult to get to and both will drain all over electrical if the drain hose pops off.

[skipperpete]

There’s something about Yanmar JH heat exchangers (and other types) that hasn’t yet been mentioned. The tube stack has a fixed position rotationally in the housing because the raw water flow doesn’t simply go in one end and out the other. The flow path does a U turn on naturally aspirated engines and 2 U turns on higher output turbocharged engines. A thin rubber spider gasket blocks the end cap to core join at a gap across the tubestack and it’s good practice to renew those end gaskets as well as the two end cap oring’s. It’s actually possible to build in an overheating problem where none previously existed even though the raw water flow is substantial into the mixer elbow if your engine runs near full load in warm sea temps.

[wsmurdoch]

I have done exactly what Russ suggested... bucket, a little 125V pond pump from Lowes, some extra hose, and Barnacle Buster in water circulated through the whole raw water system overnight. It works like a charm. I also carry a .222 rifle cleaning kit on the boat not for a firearm but for cleaning the heat exchanger when we are cruising. Its brass brush also works like a charm.

Like JimsCAL said, low water flow can be caused by a partially plugged exhaust elbow. We have had that problem twice. Google "yanmar exhaust elbow clogged" then click images to see a palace of horrors.

Our shop manual shows 1700 liters/hour at 3400 rpm for our engine (Yanmar 3HM35F). Ratioed down to 2000 rpm that is just under 3 quarts/10 seconds. We check it by holding a bucket under the exhaust elbow. There is a little splashing, so we are happy catching two and a half quarts. It is a good way to quantify a raw water flow that seems low.

[CrispyCringle]

Thanks, good point. I saw that mentioned in a video. There is a small nub on the exchanger core that aligns with the end cap for the sea water in/out side. Looked like it was in the "3 o'clock" position.

[CrispyCringle]

Originally Posted by wsmurdoch

I have done exactly what Russ suggested... bucket, a little 125V pond pump from Lowes, some extra hose, and Barnacle Buster in water circulated through the whole raw water system overnight. It works like a charm. I also carry a .222 rifle cleaning kit on the boat not for a firearm but for cleaning the heat exchanger when we are cruising. Its brass brush also works like a charm.

Like JimsCAL said, low water flow can be caused by a partially plugged exhaust elbow. We have had that problem twice. Google "yanmar exhaust elbow clogged" then click images to see a palace of horrors.

Our shop manual shows 1700 liters/hour at 3400 rpm for our engine (Yanmar 3HM35F). Ratioed down to 2000 rpm that is just under 3 quarts/10 seconds. We check it by holding a bucket under the exhaust elbow. There is a little splashing, so we are happy catching two and a half quarts. It is a good way to quantify a raw water flow that seems low.

OMG, I guess I need to check the elbow as well. May actually be the culprit. Im a little miffed because the engine has about 280 hours on it since a major, engine removed, rebuild. I have the paperwork. Cant imagine it would clog that quickly or not be looked at during a competitant rebuild. Previous owner.

Anxious to solve the mystery. Thanks for all these suggestions. Just what I was looking for.

[GreenWave]

Originally Posted by CrispyCringle

OMG, I guess I need to check the elbow as well. May actually be the culprit. Im a little miffed because the engine has about 280 hours on it since a major, engine removed, rebuild. I have the paperwork. Cant imagine it would clog that quickly or not be looked at during a competitant rebuild. Previous owner.

Anxious to solve the mystery. Thanks for all these suggestions. Just what I was looking for.

Was the exhaust cleaned during that rebuild? If not then that may be it or you really have some physical blockage in the heat exchanger.

[Russ]

A PSIn a prior post I said Yanmar approved Barnacle Buster
I was in error it's Hammerhead Marine Descaler from Bright Bay

[CrispyCringle]

So I identified what I think was the culprit for low flow out the exhaust- The sea water pump impeller was not installed correctly. Half of the vanes were flexed the wrong way in the housing. I find it hard to believe they won’t self-correct, but I guess they won’t. Also, my housing cover plate may need to be replaced. The part is on order. I’d like any opinions on the cover. Maybe just 0.01” of gap, buy my calibrated eyeball. But in the section where the vanes are compressed, I can feel the wear. The rest of it is more like just polished.

Unfortunately, I opened up the water pump last. If you want to see the process I went through, read on. I spent the last 3 days putting in the better part of an afternoon going over my entire raw water system. Good news is its fixed and I have "baselined" the sea water part of the cooling system (the boat and I have only been together for about a year).

I kind of went haphazard through the flow of the system. The boat hull cleaner guy said the thru-hull intake was clear. Strainer looked fine. Y-pipe was pristine.

The big chore is obviously the heat exchanger. It provided the correct amount of PITA. It was mainly the ability to access the many hose clamps that needed to be loosened to get all the hoses off. But first, draining the fresh and sea water. Two draincocks are located on or near the exchanger. The one for fresh water was a hex bolt and a 1/4" spigot. The sea water valve was a little 1/4 turn valve. It was super tight. I was afraid I was going to break it, but it finally turned. Then that was clogged. So I poked a wire through it and it dribbled away. I had a 1/4" ID clear hose that I used to divert the sea water to the bilge. That was enough for the first go. I left the sea water to drain open overnight and came back the next day.

Next day, with the sea water out of the exchanger, I went at the fresh water. I drained about 3/4 of a gallon of coolant into a jug, one soup can at a time. The exchanger doesn’t need to be drained completely. The level just needs to go below the end caps of the exchanger core. The clear 1/4" tubing came in handy here because I could make a U-shape and hold it up to the side of the heat exchanger and it would show the level of coolant in the exchanger. I also took apart the little 1/4 turn valve and cleaned it up. Much better now.

Once drained, and after fighting to get the hoses off of the end cap, I took the caps off. I have the "TE" turbo. The turbo did a good job of blocking access and adding an extra hose. Once the caps were off I was pleasantly surprised that the core was clean. The caps and the ends of the core had a slight amount of crystal looking growth. But the tubes were clean.

I used a bowl of Barnacle Blaster on the end caps and the ends of the core to get the crystals off. Barnacle Blaster gets a thumbs up. Worked like a charm. So, it was not the exchanger causing my low-flow issues.

A couple of notes on pulling out the exchanger core:
- You should get new O-rings for the end caps. And also the gasket for the endcap with the hoses as well.
-The core will push out of either end of the heat exchanger. Pull off the O-rings and it will be easier.
-As mentioned in an earlier post, there is an alignment dimple on the in/out side of the core. It needs to be aligned with the respective end cap, as well as the gasket, which has a cut out for the dimple.
-If you want to run a rod through the core tubes, a cheap tool is a (not sure what its called) wire rod made for holding up plants. Get it in the garden section of a place like Lowes. $2.00 as opposed to a $30 gun cleaning rod. You can improvise if your core is really dirty and you need a little abrasion effect.

So, that’s how I did that. Now on to finish my solar panel install.

NOTE: Ive got photos. How do I upload?