Coolant leak on 3208

Sean B · Post by **Sean B** » Dec 4th, '08, 22:39

Question for any of you guys with the venerable Caterpillar 3208's: have you ever had a slow coolant leak in the front/top of the engine, such that the coolant dribbled out slowly down the right (looking forward) side of the engine, just above (and onto) the alternator?

I obviosly do have such a leak.

Access to the front of my engines on my B33 is very difficult, and at the time I found it, I lazily decided that the engine was too hot to be crawling around looking for the source.

Now I'm thinking that was a big mistake, because I might not find it again without running up the engine to operating temps, and this feels like a stupid thing to do too, knowing full well that I have a coolant leak. I was hoping there was some known weak spot in that area that maybe someone knows about.

I'm guessing that maybe it's the short little hose that comes down from the heat enchanger... the only hoses I have not replaced on the boat due to severe access problems. However I have my doubts about that too, because I don't think that a slow leak usually means a hose.

BTW I found it early and before things got hot, because while cruising along I noticed the aft bilge pump running red. Of course I immediately freaked at seeing that, thinking it was a bad fuel leak (CAT coolant is red). First time in history I was very glad that I had a coolant leak.

PaulJ · Post by **PaulJ** » Dec 5th, '08, 05:51

SeanB...
I have a similar type leak on my FWC GM 350's, but it is an easy find. My engines use a kit to convert to FWC. The thermostat housing has a 3rd party spacer block between the intake manifold and the thermostat housing cover. Spacer is used to offset the plumbing/hoses from the raw water hoses. The spacer is made of aluminum. Manifold and thermostat housing cover are cast iron. No matter what kind of gasket or sealant I have tried to use, the darn thing will seap neon grean fluid... 3-4 drops, but neon green stands out on top of the black merc paint. Difference for me is that it seaps only at startup when cold. Once the mixed metals reach temp, they heat up enough the seap stops.... I use a shop towel to wipe up the drip and were dry the whole trip.

Bruce · Post by **Bruce** » Dec 5th, '08, 06:05

Sean,
Try a cooling system pressure tester to find leak without running engine.

Behind the heat exchanger there is a fitting that is common to rust out on the 3208.

Sean B · Post by **Sean B** » Dec 5th, '08, 10:38

Bruce wrote:Sean,
Try a cooling system pressure tester to find leak without running engine.

Wow I don't know why I didn't think of that first off, my Mr. Goodwrench arm is getting rusty.

I did have a leak a few years back and tried the pressure test, but it wouldn't present itself that way. I remember thinking that maybe the 3208 was set up with a valve somewhere (or maybe the thermostat itself), such that pressurizing the freshwater coolant circuit at the coolant tank didn't pressurize everything. At that time it ended up being the two very small hoses (maybe 3/8" in diameter) that run above the intake manifold, and they wouldn't show the leaks unless the engines were at operating temperature and working hard.

PaulJ wrote:I have a similar type leak on my FWC GM 350's, but it is an easy find. My engines use a kit to convert to FWC. The thermostat housing has a 3rd party spacer block between the intake manifold and the thermostat housing cover. Spacer is used to offset the plumbing/hoses from the raw water hoses. The spacer is made of aluminum. Manifold and thermostat housing cover are cast iron. No matter what kind of gasket or sealant I have tried to use, the darn thing will seap neon grean fluid

The thermostat is a serious bitch to get at on the 3208, and maybe what you describe could very well be the problem - I've never actually laid eyes on my thermostats in the four years I've had the boat. I suppose maybe it's time to tear into that part of the engines, I knew Charlie's acid-flush-in-place methods wouldn't hold me forever.

Behind the heat exchanger there is a fitting that is common to rust out on the 3208.

I'll look for that fitting. Directly on the heat exchanger body - not the tank - I presume? A little plug fitting of some sort? I'll crack the manual and find what you mean before the contortionist act begins.

The leak isn't all that slow... once I was aware of it I saw the coolant solution dribbling down from the alternator while running at idle. It took it maybe 2 - 3 hours of very light cruising (maybe 12 knots) before it bled out about 3 of it's 4 gallons of coolant. I think I was very lucky to see it before the engine went completely dry.

Many thanks for the leads

CaptMarkB · Post by **CaptMarkB** » Dec 5th, '08, 13:12

Looking at the front of the engine, your temp regulator(s) are behind the heat exchanger all the way at the top right corner of the front of the block. There are two, both behind the cover. Depending on the arrangement you have, probably have to remove the exchanger to get to those. I also had a small trickle from the exhaust manifold, there are casting voids which sometimes will start to leak out as the engine ages, which will eventually require manifold replacement (about $800 each), but your leak sounds alot more aggressive. There ar a couple of drain fittings on my 3208's on the heat exchanger that could also be a problem, as well as your zinc plugs. I have full 360' access to mine (35 Cabo EX, sorry guys), but it might be tough to spot unless run up to temp. Good Luck.

Still love my 20 Bahia Mar.

steve miller · Post by **steve miller** » Dec 5th, '08, 15:54

A (sort of) related question. I am new to the 3208. Is there a hand pump anywhere near the injector pump that can be used to pump fuel to the injector pump in case of "sucking air"? Cummins and Yanmar both had one. I haven't found one on the Cat yet...........

CaptMarkB · Post by **CaptMarkB** » Dec 5th, '08, 16:11

Steve,

There is a hand plunger pump by the primary fuel filter on the engine. It's a knurled round knob about 1 1/2 inches in diameter at the top of the filter. Turn the knob counter clockwise and pull out the plunger to pump. You'll know when it's done. Remember to tighten the plunger back when done. This should be used to fill replacement fuel filters before restarting, and can also be used to re-prime the engine if needed. My experience has been that you should only have to "crack" 2 injectors on each side to bleed the engine for restarting. (might have been an option)

Bahia Mark

Charlie · Post by **Charlie** » Dec 5th, '08, 18:41

I will go take a look at mine tomorrow in the day light. There is a fitting called a water sleeve. Looks lkie a short piece of steel pipe with O-ring groves in each end. You need a water sleeve removal tool (big fing screwdriver) to slide it "into" the motor to remove the head. Been there done that. One of the o-rings could have $hit the bed. I will take a look tomorrow to see what else could have let go. Hopefully it is just a hose.

Capt.Frank · Post by **Capt.Frank** » Dec 5th, '08, 20:37

Sean,
My guess would be temp sender, just changed mine. Mine motors were lossing coolant small amouts at a time. Then last month found the leak water pump was leaking as fast as it was put in. But the water pump would not leak on to alt. Try using a camera and take picturs and look at them on the computer. If you can't get a good look due to space.

Frank

steve miller · Post by **steve miller** » Dec 6th, '08, 09:43

Thanks Mark, that's a help!

Charlie · Post by **Charlie** » Dec 6th, '08, 11:48

OK took a look. It could be the aforementioned water sleeve. There is a hose coming from the manifold passing right over the alt. There are two hoses high enough on the front of the motor to maybe leak or spray on the alt. One big one and one little one. If she is leaking good a pressure tester will show it up. Pump her up to 10-15 psi and it should leak if it is a hose. Most of the time a gasket leak will not show up when cold even though you are pressurized. I always carry a pressure tester on board.
Good Luck

Sean B · Post by **Sean B** » Dec 9th, '08, 00:36

Thanks Charlie - your advice has always been right on. I'm not at all familiar with this water sleeve that you speak of... but will go looking for what you're talking about with great enthusiasm, thanks again

terand_1 · Post by **terand_1** » Jan 16th, '19, 16:33

Two Cat 3208 Turbo owner here. About six months ago, noticed a small leak from about where you say. The previous owner used CAT Extended Life Coolant (ELC-Red/Rusty looking stuff) on one of the engines...never should have used it. I went to start the engines up to get them ready for the new year and the ELC coolant seeped its way through the Water Pump Shaft...coolant spraying everywhere! Now I had found the source of the leak.

New Water Pump, three coolant flushes, and new DEAC (Mobile) Purple coolant, and new belts later, all works fine.

The other engine has the green phosphate/silicate coolant...next project is to flush that and switch to the DEAC/Mobile...any thoughts?

bertram31.com

Coolant leak on 3208

Coolant leak on 3208

Re: Coolant leak on 3208

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