Blocked Manifold Coolant Passage

[Triton#335]

Pulled the manifold to re-hab a corroded hot section. The photo below shows the drain plug near the #4 exhaust port. Fully constricted with rust. Creates a small hot section on the lower aft section of the manifold (bubbles paint).



Any ideas out there on how to clear this out?

Dave

[Don Moyer]

Dave,

Those drain holes are very difficult to clean out. You can usually drill or tap your way straight in for approximately 3/4" but then you'll run out of hole. The hole takes a 90 degree turn to the left (toward the front of the
manifold) and up at approximately 45 degrees.

The best way to open this drain passageway is to remove the freeze plug so that you can dig around from the inside of the jacket in the direction of the drain hole as you are working your way in from the outside. In our shop we use a drill bit (approximately 1/8") that we ground to a rather sharp flat edge on one end - sort of like a tiny Cole chisel.

After tapping from the outside and inside of the hole as far as we can using the drill bit, we try to drive a common 12 or 14 penny nail from the outside. The nail is soft enough to conform to the shape of the hole and will usually make it through the final restriction before collapsing. If it does collapse, use a new nail. It sometimes takes 2 or 3 nails.

By the way, the hot spot isn't so much created by the clogged drain hole but by the fact that the lower part of the cooling jacket is filled up with crud. This will become clear when you remove the freeze plug.

Don

[Triton#335]

Thanks, Don. Never removed a freeze plug before. Should I drill it out or will it pry out?

Sincerely, Dave

[Don Moyer]

Dave,

Here is a tech tip we prepared on freeze plug removal and replacement sometime ago. It's more information than you asked for, but it's easier for me to send you the whole hamburger than to remove the pickle.

Don

REPAIRING AND/OR REPLACING FREEZE-OUT PLUGS:

Freeze-out plugs were originally installed over a small ridge cast into the lower part of the hole in the block, head or manifold. Here are your options for repair, starting with the least invasive and leading to the more complicated procedures:

1) If the plug has some dome shape remaining, you could take a flat punch (a 1/2" bolt will work) and flatten the plug. These plugs are designed to seal around their OD by flattening out their dome shape. Flatten the plug by pounding in a circular pattern around the center, but not directly in the center. The challenge is to flatten the plug without causing a concave dimple in the center, which would reduce the ultimate outward expansion of the plug.

2) If the plug is already flat, you may be able to seal it using epoxy of the type West Marine sells in small repair kits. Before using epoxy, be sure to clean the surface of the head and plug extremely well.

3) You can replace the plug with a new one from our online catalog (Product number: OBLK_14_125), and reseal around its circumference during installation. Old plugs can be removed by drilling a small hole in their center and then inserting a punch and prying the cup out by pounding on the side of the punch. Since the inner circumference of the hole will probably be less than perfect, we recommend the use of JB Weld to seal the new plug. Flatten the new plug as in the first option above.

4) If, after removing the old plug, you discover that the ridge in the casting is deteriorated to the point that it will not support the pounding it will take to seat a new dome shaped plug, you can ream the hole to a slightly larger size, and install a "cup" type plug. In our own rebuilding work, we routinely ream holes for the larger plugs (used in the block and head) to 1 - 1/4" and to 15/16" for the smaller plugs (two used in the manifold and one in the head).

5) For on-boat repairs where poor access prevents repairs involving reaming etc., there are rubber expansion plugs available from many automotive parts stores which may work to seal a hole (at least on a temporary basis) that is too deteriorated to accept a dome type plug, without the need to ream the hole.

Don

[Greg]

Manifold hot spot

My 40 mile trip out of the Sacramento Delta went well last week .. with my rebuilt A4 running like a watch. However, I've noticed the paint burning from the front corner of the maniflod. I'm assuming it's a blocked water passage like in this post. Any ideas ? My plan is to pull it and try Don's process & or have it boiled out. I'm also wondering if the freeze plugs are a standard type and size from a good auto parts store ?
Opinions .. comments welcomed as always

Regards, Greg

[Administrator]

Greg:

What kind of paint did you use?

Bill

[Dave Neptune]

Hot Spot?

Greg, the engine looks awfully fresh to be having such a concentrated hot spot. The hot spot does not seem to be affecting the adjacent area of the block and it appears somewhat glossy in your photo. This is a shot in the dark here but are you sure you may not have a crankcase or exhaust leak discoloring the manifold? Try wiping it down with some thinner. Usually most spray paints will peel drastically before turning black and it looks almost air-brushed black on the end. Besides this may be less work just to reseal.

Good luck
Dave Neptune Ericson 35

[Greg]

Manifold hot spot - paint

The paint is POR15 with their engine enamel over it.

Greg

http://www.por15.com/

[Greg]

Old paint job

I just remembered I had a picture of my manifold before I re-painted the engine. Same hot spot it seems. While I had the manifold off, I admittedly just cleaned out the obvious, replaced the studs, gasket and flange and put things back together. It looked pretty good .. but I did'nt dig deep or pop the freeze plugs.
I just called an engine shop who said they could bead blast or flush with a detergent if I want to go that way. But if there is a blocked passage in the area I should do a simular surgery to the one Don outlined .. I suppose

Thanks, Greg

[Greg]

picture

Sorry .. here's the old picture

[rigspelt]

I've noticed the paint burning from the front corner of the maniflod.

Here is part of a photo I took of the front of the engine prior to our refit last year. Same hot spot. I have not looked yet to see if the new paint is doing after our first summer in the water following the refit. I had flushed the block, so hopefully the passages cleared ...

[roadnsky]

I have the same discoloration in the same spot.
I have no temperature issues whatsoever and good water flow with the exhaust.
Hmmmm...

[Dave Neptune]

Hot spot

Guys, I will check my A-4 this evening as I will be going by the boat on the way home tonight. The hot spot could just be a part of the manifold that does not have water "around" where the exhaust enters the manifold. In that case it is just how it may/will look after a while. Most of us who "tinker" tend to try and increase performance and economy figures which were not a major criteria when these motors were designed. Running a bit leaner with the timing at max efficiency will raise the exhaust gas temps considerably and that could be what we are seeing as well as why.

Greg, that paint looks really good, thanx for the link. I am always trying to paint old rusted stuff and that is a new one to me. I am amazed it stayed glossy after getting hot enough to change color.

Jerry, do I detect a copper pipe fitting on your PCV hook-up? That's how I did mine.

Dave Neptune

[roadnsky]

Dave-
You read my mind on the Hot Spot!
And yes, that is indeed real copper...

[Greg]

Manifold hot spot on 3 engines

Jerry & Dave,

Thanks for taking a look at your engines. I had planned on pulling the manifold today .. but may hold off and see what comes of this. I have plenty of other projects for sure. Pretty ironic all the manifolds have high heat in the same spot.
I've been happy with the POR15 paint(s) pricey .. but gone a long way. I've painted 3 coats on the A4, my new engine beds and steering brackets with a pint of paint. It's like a flexible epoxy coating. We'll see how it holds up in a tough envioronment ?
I'll be at the boat for a few days, but try and look in on this thread before going invasive.

Regards, Greg