3gm30f heat exchanger stuck!

[PGIJon]

My engine began overheating this weekend. This morning as part of my detective work I decided to begin with the heat exchange. A couple of weeks ago I replaced the impeller, so I decided for the moment, I would leave that alone.... for the moment. After draining enough coolant, I removed the end caps of the heat exchanger housing. Low and behold a piece of rubber was caught in the tube of the housing partially blocking the raw water flow. This did not completely block the water since I checked that water was being expelled while the engine was running.... Looking back it flow did seem smaller than usual. That should have been a sign! I also noticed that the raw water hose leading from pump to the exchanger was also a bit twisted. Next time I'll double check the hoses for twists!

Anyway I decided that while I had the exchanger open I would remove it and have it cleaned. It's stuck..... I tried to gently tap it out with a block of wood and a hammer...to no avail.

Before I do any damage, I was looking for suggestions on how to remove the exchanger.

This overheating problem did not cause us to miss out on some great sailing this weekend. We did take this opportunity to practice sailing up the channel and into our canal and docking under sail. We're going to do this more often. I suppose I've been spoiled by our Iron Genny! This brought back found memories of weaving between moored boats and praying I did smash into any of them when I first learned how to sail on a motor-less 23' day sailor.

Thanks
Jon

 

[Allan12210]

Hi Jon,

I've attached a schematic of the heat exchanger for your review. The big O-ring is probably stuck from years of heat.My first thought would be to leave it alone until other avenues are exhausted. As you probably know the face of the exhanger is divided into thirds. The water flows through only one third of the holes from front to back, then towards the front in the next third of holes and finally back and out with the final third. So, it doesn't take much of a chunk of material to significantly decrease the flow rate. The next area to trap junk is the fitting that screws into your mixing elbow. I've had mine completely obstructed with what feels like concrete. I've discovered that after taking the fitting off (mine's a street elbow, some are straight male connectors). It took reaming with a screwdriver to clear it. Also ream out through the hole into the mixing elbow as best you can.

Back to your original issue of cleaning out the heat exchanger. The area most susceptible to blockage is the interior of the tubes. I found that the diameter of them is just slightly larger than a 1/4" drill bit (probably because its metric). I bought a 16" long 1/4" drill bit and use it to clean each tube every 2-3 years. Chuck it in your drill and only remove the front cap (I know, too late). Run it slow, back and forth, only advancing about 2 inches at a time. If there are a lot of deposits in there it will quickly clog the flutes of the drill, hence the need to only do a little bit at a time, then extract and knock the crud out of the bit. After the reaming, put it back together and check operation. After running for a bit, check that flitting again on the mixing elbow as there may be residual loose stuff flushing out that may clog it. I know this from experience. The exchanger will be more efficient at this point as evidenced by a thermometer I installed and you may see an increase in flow. Only if this doesn't work would you want to consider further dis-assembly. At that point you may want to remove the entire heat exchanger tank if it won't budge. If you can get away with it, try and leave it be.

Good luck.

Allan

 

[kloudie1]

Ditto, Allan.. the outside of the tubes are covered with a guard so you really can't get at them much anyway. The clean coolant is on the outside of the tubes so not likely to have fouling there unless that has not been maintained. .If the big O-rings are not leaking or cracked, it would not be necessary to remove the tube bundle. I use a brass rifle barrel cleaning brush to clean the tubes. but as Allan says, you can (Very Carefully) use a drill bit too..
Once the end caps are both off, the bundle should slide out.. it could be that someone in the past used a gasket material around the big O-rings.. Definitely replace the end cap gaskets and if you do tap the bundle out, use new O-rings. As I recall, the bundle can slide out either way and is not "shouldered" into the housing. The O-rings are the only thing holding it.

 

[PGIJon]

As always thank you Allan and Claude for your help, advice and PDF's! Yesterday, before I saw these responses, I ordered an engine cleaning brush set and a .22 gauge rife cleaning kit. Hopefully that will clean it out... If it doesn't I'll order the drill bit Allan mentioned. Wish I had the hands of a surgeon.

I ordered both the cover "Peace" o-rings, the cylinder o-rings plus the pin Part # 124790-44470... which I'm not quite sure where that goes... I should have all this later today and will begin to go to work on it all.... lots of build up on the inside of the covers as well. While I have this off.. I'm going to try and pull the mixing elbow. There's a lot of rust on the elbow's flange bolts....

Thanks for the help! I'll update and may have a few additional questions! Have a great day guys!

-Jon

 

[PGIJon]

I've also found that my impeller was torn apart! The attached picture explains how I will prevent this from happening again in the future! -Jon

 

[kloudie1]

Bummer about the seacock, Jon.. but ya probably found the overheat problem in that shredded impeller .
The little pin holds the tube bundle exactly where it is supposed to be. It locates the bundle such that the openings in the bundle cover are in the correct position for coolant circulation. One end of the pin goes into the cover and the other goes into the end plate (tube sheet) of the bundle.

 

[PGIJon]

Thanks Claude! This is the first time, I've let it run over 30 seconds without opening it... Now I'll remember... hopefully! After cleaning the inside of the cover, I found the pins.... I'll probably leave the original ones there since I would need to drill them out and they are still well enough in tack to do the job. Thanks again! -Jon

 

[kloudie1]

I did that same job a few years back and as I recall, the toughest part was lining up the bundle to the rear pin before installing the front cover.. I remember putting a very little bit of tacky silicone gasket stuff on the bundle ends to hold the gasket in place then inserting the bundle from the rear with gasket and pin in place and held there by hand while holding pressure from the front to keep the pin from disengaging.. then hand tight a couple of the rear end cover bolts.. and finally install the front cover kind of a tricky balancing act to get it all done while keeping everything in place. Good Luck with it.

 

[PGIJon]

Thank you for the advice Claude! I was able to remove the cylinder this morning by tapping a 2x2 piece of wood against the cylinder. It's surprisingly clear. I did us a hose to shoot water through the heater exchange earlier this year. I noticed a bunch of calcified materiel exit the exhaust when I did that. I also removed the mixing elbow and elbow this morning. I'm going to put my tiny pipe camera down it and take a look. Thanks again Claude and Allan! -Jon

 

[woodster]

I've also found that my impeller was torn apart! The attached picture explains how I will prevent this from happening again in the future! -Jon
View attachment 115793

a good way to make sure you have it in the open position would be to either rig up a micro switch on the valve to keep the solenoid circuit from activating when closed or an alarm buzzer that sounds when it is closed when you turn on the key switch ...we used to use cam actuated micro switches in the elevator business to limit the elevator from running if a landing door was ajar or open ...just something to ponder

 

[PGIJon]

Woodster... I'm pondering, contemplating, deliberating, considering... but I can't figure out an good way to attach a micro switch to the valve. Any thoughts, because I like the idea.... -Jon

 

[woodster]

I will have to do some research and shopping to make it a reality but it is do able there may be some f glass work involved as ever location in the hull is not the same as is also the sea cocks are different for now just putting the ignition key on the seasick lever is the cheapest and simplest way you always have to go to the seasick and get the key to run your engine but if when through you don't return the key to the seacock and close it it is a lost cause

 

[Claude L.-Auger]

Jon, bummer indeed about the seacock !!! I use a very simple trick when I shut the water intake to the engine: I put the key on the shut ball-valve handle. Can't start it without retrieving the key which of course also reminds me of turning seacock open. Good luck with the cleaning.

 

[eianm]

using a drill bit to clean out old tubes is fraught with DANGER! Best to use a gun barrel cleaning brush- much more gentle on the aged copper tubes- this aged copper ends up pretty thin, you don't want to risk putting a hole in a tube wall!

 

[eianm]

when i recently removed my heat exchanger core, i had to use quite a high level of force- i used a larger hard rubber mallet and a piece of wood and literally hammered it out- as i said- it needed BIG blows! Certainly a bit scary!

 

[Dan Johnson]

Hey guys! Before doing all that fancy microswitch wiring and installation, consider putting a keychain on your engine key and hanging it on the closed seacock valve handle after you shut the engine down. You'll need to retrieve it to start up, forcing you to remember to open the seacock before you do so.

Works for me!

 

[PGIJon]

Key on the sea cock seems to be the consensus! I'll start doing that but I still like the idea of a switch.... Have been putting it all back together this morning and hope to be running a very cool engine by tomorrow. Thanks everyone! -Jon

 

[PGIJon]

After, replacing the impeller, replacing the thermostat, cleaning out the heat exchanger, replacing all gaskets, pulling and inspecting the mixing elbow assembly as well as replacing the gasket that butts up against the engine block. The engine is running cooler than I've ever seen it in the past 3 years! It held 160 even with the prop engaged at full throttle.

Most surprising was that I could actually do this myself! Well.. myself with the help of all of you guys!

I was also a bit surprised at how smaller than expected volume of water that passed through the heat exchanger. I have a video of it, but I'll put that up later in a different post.

-Jon

 

[Mark48]

I always listen for the sound of exhaust discharge when I start the motor. If it doesn't sound right I do a quick visual. Internalize the sound of the exhaust so it becomes an instinct.

 

[ELMAX]

A little advice, I put a filter between the impeller is the entrance to the heat exchanger, so if you break the impeller blade rubber stops in the filter, and does not go in the heat exchanger, the filter must be put contrary, to have more residential space in the direction of water inlet, the rubber impeller route, it goes into the filter with more residential space for passing water.