Cat 3208 NA heat exchanger reassembly and questions

I've got the core bundles cleaned up and ready to reassemble.


1 - Should I use any sealant on the gaskets? The last person seems to have assembled them dry. There was some leaking. However I´m concerned that if I use sealant the bundle core will be near impossible to get out in future.

2 - What lube for the O-rings?

3 - Core bundle alignment. When removing the end cap with the O-ring I noticed on both engines the end of the bundle was not concentric with the tube. There is no play in the assembly when the bundle is all the way in. I can think of a couple of work-arounds. Remove some material on the bundle´s (for lack of a better term) internal brackets. Or. Carefully fit the end cap and O-ring then force the end cap holes to line up with the tube holes. The reason for the concern in alignment is two fold. On one engine the previous installer had just pushed the end cap over the bundle slicing the O-ring.

4 - Corrosion, pitting. On the engine with the damaged O-ring there is some pitting at the bottom of the tube. Because that should only see coolant it concerns me the damaged O-ring was allowing coolant and sea water to mix causing the pitting. Unknown, and just speculation. These engines are 1983 vintage with about 4000 hrs on them


Some 3208s have plastic end caps on the heat exchanger. These engines have cast metal caps. Probably bronze.

I’ve had good luck installing the gaskets dry, but of course that’s going to depend on the surfaces after this many years. Start dry and see if it works. I’ve had mine off a number of times and don’t recall the concentric issues you note, but it’s been awhile. Use o-ring lube or I always have a tube of superlube on hand I use for a ton of things. Use extra lube where the pieces come together and just try to work it and be as gentle as you can until things slide where they are supposed to.

Bronze end caps are the best IMO. If steel triple check the integrity of the split side, where that thin strip of metal runs.

Thank you for the reply. I'm not sure gentle is possible. To get the cores out I had resort to a block of wood and a 2 lb hammer until they were about half way out. It's going to be interesting.....

following this... also have 3208's... TA version, but I think the HX are the same, lol, right???

Scottwb96 said:

following this... also have 3208's... TA version, but I think the HX are the same, lol, right???

Click to expand...

I think they're very similar but not the same. You likely have plastic end caps and more zincs. It's worth digging through boatdiesel.com.

I definitely don't have plastic endcaps... lol, excuse the mess in the middle of an engine room camera install...

Yours look quite similar. I'm guessing the core bundle, tube the bundle slides into and the expansion tank are the same. I do see what looks like more zincs in yours. I would expect some differences in connections due to yours having after coolers.

I've solved the misalignment, the core not concentric with the barrel. A budd who is a real mechanic suggested putting the stbd core in the port. It worked a charm and the cores no longer need to be forced in and out with a 2 lb hammer.

It's not perfect and the shadows make it look worse than it is. I think it's within the tolerance of the holes in the caps and the ability of the core to flex a bit.

For the pitting on the barrel flanges I'll use RTV between the flange and gasket. Other gasket surfaces will go together dry so that I can take it apart in future.

Scottwb96 said:

I definitely don't have plastic endcaps... lol, excuse the mess in the middle of an engine room camera install...

Click to expand...

Not the clearest photo, but those look like the generation 2 plastic end caps to me. The generation 1 plastic end caps had thinner flanges and could warp easily.

3208 Heat Exchanger Bundle gaskets

I recently had to replace my heat exchanger bundle core on a Cat 3208 T, I have plastic bonnet end caps, I noticed the parts book has 2 O rings for one cap the cap away from the raw water pump. and 1 O ring for the cap closest to the raw water pump. I have those but have a single large gasket that has gasket material through the center which means it goes on the outside of the lip of the core bundle. According to the parts manual there is just 1 gasket at this end but if I follow that suggestion that leaves bare metal of the core bundle against the tank. My old bundle core had a single gasket between the bundle lip and the tank. Should there be 2 gaskets? One between bundle core and tank and another between plastic cap and bundle core?
The photos provided show my old gasket with no gasket material in the middle and the new one that has gasket material that mirrors the end of the bundle.
See photos and thanks

Wade Cordy
M/V Synergy

It's been just long enough I can't remember for sure. My suggestion is to look at the images in the parts book. Mine made it pretty clear what goes where.

You must use a gasket (4W6950 on my TA engines) between the core flange and the HE body. You also must use an o-ring (6V5504 on my TA engines) on the end of the core that does not have a flange.



If you have the newer style bonnets with groves for o-rings, you do not need any more gaskets, just an o-ring in the groove in each plastic bonnet. I don't have that 0-ring part number handy.



If you have the older bonnets, you need the same gasket that you used between the core flange and the HE body (4W6950 on my TA engines) at the opposite end, and the gasket you showed with the dividing line in it (4W6949 on my TA engines) at the core flange end.


The gaskets or o-ring-gasket-combo that go against the HE body are there to keep the coolant in. The o-ring on the core and the o-ring or gasket against the outside of the core flange is there to keep the sea water in. Hope this makes sense.

Thank You