Exhaust manifold problem re-post w/pic's

[hanleyclifford]

Well it certainly seems that water flows only along the "outside" surfaces of the manifold, so that the portion closest to the block does not have a water jacket and is instead a solid casting. So it would make sense that that side will be significantly hotter than the outside surfaces.

Exactly, and if there were a jacket blockage in that area it would only be manifested by localized overheating while water flowed elsewhere thru the block.

[67c&ccorv]

This "problem" would be easily solved if we would all use Hi-Heat BBQ paint on our exhaust mainifolds...as I have recently done.

[wmmulvey]

You might find this thread interesting.

Among other things, there's a photo of a manifold cut in half showing the L-shaped water passage that runs along the top and side of the manifold. I believe that is the only water passage.

Is that another water passage on the bottom?

[romantic comedy]

I think what you are looking at is the intake passage.

[Loki9]

Here's my interpretation:



Thanks to the original photographer for the manifold postmortem.

The UHS occurs because the water jacket doesn't completely cover the #1 exhaust port and the water flow in that corner of the jacket probably isn't very good.

[hanleyclifford]

I wonder if better cooling could be achieved around the UHS if the coolant was directed thru the forward expansion plug rather than the 1/2" NPT hole on top of the manifold.

[wmmulvey]

Exhaust manifold problem re-post w/pic's

I went out to the boat yesterday to try the "Thatch modification" (on the used manifold) that Shawn suggested.

I took off the t-stat housing to change the hose but decided to just remove the t-stat and see what happens. I did not do the "Thatch modification"

PROBLEM SOLVED.......Bad t-stat

Instead of 300 + degrees the temp went down to 220. After running for about 15 minutes the temp went down to 190 and no hot spots. Seems like the water pressure pushed out some loose gunk leftover from the mauriac acid cleaning.

Thanks for all your help. I sure learned a lot from all the discussions on this thread.

Bill

[thatch]

"Heartbroken"

Bill,
I am crushed that you decided not to convert to the "thatch" hose route.
Actually, my approach to plumbing an engine comes from several years of building cooling systems from scratch and running the hoses according to things like heat and gravity. Most of the A4s still running, are plumbed the way that they came from the factory and are doing just fine. My change on the A4 involved mainly two things. First, by running the coolant (water or coolant) into the lowest port of the manifold, you minimize the possibility of air pockets as much as possible. Secondly, by injecting the coolant coming from the block to the potentially hottest point of the manifold where the gasses from all 4 cylinders are passing, you may be able to "stabilize" the overall temperature of the manifold. In the stock configuration, the coolant is injected very close to the exhaust port of cylinder #1 and is then is being asked to cool cylinders 2,3 and 4 on it's way down the line. By reversing the flow I feel that it is possible that some minor "longevity" benefits may be gained. At this point in time, where all of our engines are over 30 years old, the most important thing is to make sure that there is still adaquate coolant flow to cool things down. I am a firm advocate of the fresh water conversion to lengthen the life span of these wonderful little engines.
Thatch

[Dave Neptune]

Heads up

Bill, if you just acid flushed I suggest that you pull the "exit" fitting where the water comes out to go to the exhaust. It is a common spot for debris to collect after flushing or digging around in the coolong system. I'd take a look after an hour or two of running to see if anything has been collected there. Worth a look if your "not sure".

Dave Neptune

[thatch]

Descaling

To expand on what Dave said, normally during a rebiuild involving an old block, I will "tap away" with a "light weight" hammer around the exterior, trying to loosten up the scale buildup in the water jackets as much as posible. Many times the pieces that break loose are big enough to plug the water fitting holes. By using screw drivers, coat hangers and other probes, it is normally possible to remove a considerable amount of "junk". Having the block as dry as possible during this process generally yields the best results.
Tom

[wmmulvey]

Thanks for the updates

Bill

[wmmulvey]

Bill,
I am crushed that you decided not to convert to the "thatch" hose route.
Actually, my approach to plumbing an engine comes from several years of building cooling systems from scratch and running the hoses according to things like heat and gravity. Most of the A4s still running, are plumbed the way that they came from the factory and are doing just fine. My change on the A4 involved mainly two things. First, by running the coolant (water or coolant) into the lowest port of the manifold, you minimize the possibility of air pockets as much as possible. Secondly, by injecting the coolant coming from the block to the potentially hottest point of the manifold where the gasses from all 4 cylinders are passing, you may be able to "stabilize" the overall temperature of the manifold. In the stock configuration, the coolant is injected very close to the exhaust port of cylinder #1 and is then is being asked to cool cylinders 2,3 and 4 on it's way down the line. By reversing the flow I feel that it is possible that some minor "longevity" benefits may be gained. At this point in time, where all of our engines are over 30 years old, the most important thing is to make sure that there is still adaquate coolant flow to cool things down. I am a firm advocate of the fresh water conversion to lengthen the life span of these wonderful little engines.
Thatch

Thatch,

I intend to do the "thatch" hose route. The thinking is very logical and I agree with it.

The temperature in my cabin was 96 - 98 degrees and I wanted to get out as fast as I could.

My priority right now is to get my mast up and get sailing. That project will be down the road for now.

Bill