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Old 03-29-2021, 08:07 AM
Airshac Airshac is offline
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Questions about my ďnew to meĒ engine.

Just getting to know this engine. Coming over from VW buses and aircraft maintenance. The engine seems very easy to work on.
I did a compression check and had 3 cylinders at 70 and one at 65. How is that? I donít know anything about the history of the engine.

Secondly, I think the thermostat is stuck. I guess by default, if it malfunctions it will stay in the open position. I ran the engine for twenty minutes and water was coming out the exhaust but the water temp gauge never moved. I was concerned to run it longer because I donít know if there is a way a bad thermostat could cause water to by pass circulating through the engine? Where is a good source for a new thermostat?
Thanks for the help!

Last edited by Airshac; 03-30-2021 at 05:14 PM. Reason: Fat finger in title.
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Old 03-29-2021, 10:08 AM
Hawkeye54 Hawkeye54 is offline
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Welcome to the site ! There is a lot of help / expertise on the A4 available here. If you check the 'home page' and the 'online catalog' , a lot of your questions will start to be answered . . . Hope that helps !






Rick
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Old 03-29-2021, 10:32 AM
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Welcome!
Most if not all parts available at our sponsor Moyer marine.
Strongly recommend to get the Manual, a mine of information on maintenance troubleshooting etc..

https://www.moyermarineforum.com/for...&postcount=159

you will find a lot of help here!
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Old 03-29-2021, 01:34 PM
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Welcome and back to your original questions. Your compression is OK, not great but OK. Also, if the engine hasn't been ran regularly, you will likely see that compression increase a bit with regular use. there are techniques of putting Marvel Mystery Oil in the cylinders after use to let is help clean any deposits on the rings, etc.

How do the spark plugs look? That's a great indication on how the engine is running.

Regarding cooling, are you fresh water or raw water cooled?
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Old 03-29-2021, 03:23 PM
JOHN COOKSON JOHN COOKSON is online now
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I would be sure the temp gauge, wiring and sending unit are working.
Is there a valve on the bypass after the tee fitting between the engine and thermostat housing?

ex TRUE GRIT
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Old 03-29-2021, 06:52 PM
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If you're raw water cooled and located anywhere other than the tropics, your engine takes forever to warm up even with a thermostat. When I was raw water cooled I rarely saw temps greater than 120į (late model cooling system, Southern California water and original Holley 3 spring dual action thermostat).
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Airshac (03-29-2021)
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Old 03-29-2021, 07:34 PM
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Quote:
Originally Posted by ndutton View Post
If you're raw water cooled and located anywhere other than the tropics, your engine takes forever to warm up even with a thermostat. When I was raw water cooled I rarely saw temps greater than 120į (late model cooling system, Southern California water and original Holley 3 spring dual action thermostat).
On the coast of North Carolina sitting at the slip running for that time at about 1500-2000rpm. Next weekend Iím moving the boat about 6 miles, probably motoring most of that so Iíll keep an eye on it. There wouldnít be away for water to by pass circulating through the engine if the thermostat malfunctioned would there? I donít think so. It is raw water cooled.
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Old 03-29-2021, 07:36 PM
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Quote:
Originally Posted by ronstory View Post
Welcome and back to your original questions. Your compression is OK, not great but OK. Also, if the engine hasn't been ran regularly, you will likely see that compression increase a bit with regular use. there are techniques of putting Marvel Mystery Oil in the cylinders after use to let is help clean any deposits on the rings, etc.

How do the spark plugs look? That's a great indication on how the engine is running.

Regarding cooling, are you fresh water or raw water cooled?
Raw water cooled and itís been sitting for almost two months. The plugs had black soot on them but the tips looked to be in good shape.
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Old 03-29-2021, 08:10 PM
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Quote:
Originally Posted by Airshac View Post
There wouldn’t be a way for water to by pass circulating through the engine if the thermostat malfunctioned would there? I don’t think so. It is raw water cooled.
If I understand the question correctly, that's exactly what the bypass does when the thermostat is closed, bypasses the engine and sends water directly to the manifold. Without testing (stove top pan test?) I wouldn't get fixated on a thermostat malfunction. For that matter, John Cookson's thoughts are equally viable, perhaps a gauge/sender/associated wiring problem. It needs to be checked.

Do you have an infrared temperature gun? It could provide a wealth of information. His question about a bypass valve is important too.

Another thought: are you sure it even has a thermostat? Have you removed the stat housing and had a look inside?
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Last edited by ndutton; 03-29-2021 at 08:16 PM.
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Old 03-30-2021, 12:59 AM
JOHN COOKSON JOHN COOKSON is online now
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Quote:
Originally Posted by Airshac View Post
. I was concerned to run it longer because I donít know if there is a way a bad thermostat could cause water to by pass circulating through the engine?
Are you familiar with a two stage thermostat? The original two stage thermostat in the A4 balances water going through the engine and water going around the engine (the "bypass").

As advised, I would hold off on ordering a new thermostat until you confirm (1) you have a thermostat and (2) if you do have a thermostat that it is working incorrectly.

ex TRUE GRIT
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Old 03-30-2021, 08:19 AM
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Quote:
Originally Posted by JOHN COOKSON View Post
Are you familiar with a two stage thermostat? The original two stage thermostat in the A4 balances water going through the engine and water going around the engine (the "bypass").

As advised, I would hold off on ordering a new thermostat until you confirm (1) you have a thermostat and (2) if you do have a thermostat that it is working incorrectly.

ex TRUE GRIT
Thanks for the input! I need to dig in to it a little deeper but for the time being Iím going to remove the thermostat just so I can move the boat a few miles knowing that water is circulating through the engine. I realize this wonít allow the engine to operate at optimal temperature but itís better than having no water circulating. Is there a problem with this line of thinking for this engine?
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Old 03-30-2021, 09:26 AM
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Removing the thermostat will not force water through the engine, quite the opposite. To achieve your temporary goal you must have a restriction in the bypass hose, typically a valve in the bypass loop that can be closed partially or even completely.
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Old 03-30-2021, 03:08 PM
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Quote:
Originally Posted by ndutton View Post
Removing the thermostat will not force water through the engine, quite the opposite. To achieve your temporary goal you must have a restriction in the bypass hose, typically a valve in the bypass loop that can be closed partially or even completely.
Neil--

That pic is likely the prettiest bypass valve install I've ever seen.
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Old 03-30-2021, 08:12 PM
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So this is a picture of my engine. The raw water comes in at the orange handle on the right hand side. What can I check with the engine running to make sure water is circulating through the engine? I verified that water was being pushed by the pump and discharging from both hoses on the left. Water leaves the engine in the black hose on the left goes to the water heater then to the exhaust via the black/green hose Name:  B1F0FE82-58A2-4D91-9C7D-8A7220EDA55E.jpg
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Old 03-30-2021, 09:50 PM
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You always have full flow through the manifold regardless of thermostat position, even if you have no thermostat. As I offered earlier, an infrared temp gun measuring head temperatures would be an excellent diagnostic tool. Also, you can guaranty water flowing through the block if you obstruct the bypass hose, thermostat installed or not. If there's any uncertainty, the bypass hose is the one right next to the starter. Even a pair of vice grips will do in a pinch. It's a temporary measure if you need it until you try the many other suggestions that have been posted.

Here is a link to a flow diagram that should help. The late model diagram applies to you.

https://www.moyermarineforum.com/for...36&postcount=1
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Old 03-30-2021, 10:15 PM
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Thanks for the diagram! I know there have been a lot of good suggestions here. Iím not at the boat during the weeks days so just trying to gather as much info as I can before I head back down there this coming weekend.
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Old 03-31-2021, 11:13 AM
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Quote:
Originally Posted by ndutton View Post
You always have full flow through the manifold regardless of thermostat position, even if you have no thermostat. As I offered earlier, an infrared temp gun measuring head temperatures would be an excellent diagnostic tool. Also, you can guaranty water flowing through the block if you obstruct the bypass hose, thermostat installed or not. If there's any uncertainty, the bypass hose is the one right next to the starter. Even a pair of vice grips will do in a pinch.
I'll second Neil's advice to acquire an infrared gun to be certain what the engine temps are.
From there, you can get a permanent temp gauge working and you'll know that it's working properly.
While you're verifying temps, try using the vise grips on the bypass (use a cloth to protect the hose) and observe the temp changing.

Those simple tests will give you some confidence in your engine cooling for your upcoming trip.

Finally, here is a very good read related to your current questions.
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Old 03-31-2021, 05:47 PM
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Wow...A-4 in the bilge!!
Not too many boats did that.
Hughes 38 is the only one I know of!??!!

Welcome!
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She is even happier with fresh paint on the topsides!

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Old 03-31-2021, 06:58 PM
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A-4 in the bilge on my E35MkII, almost completely below the water line right on the keel. Only finger clearance in some spots along the pan as she sat down in the turn of the bilge. The dinette seat was above the engine.

They sit pretty deep in a Cat 30 as well.

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Old 04-01-2021, 09:54 AM
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What has helped me understanding cooling...and bypass valve..

Context. I considered myself a redshirt freshman last year owning my first A4 since August. Never did much mechanical, though always loved when I did. I am something like a A4 freshman this year.

The greatest help besides studying and reading threads here especially search on running with or without thermometer and all of the great debates on running colder or running hotter:

1) The Moyer publications.
2) Slow experimentation with infrared thermometer
3) Studying rebuild threads here and noting hot spot and water jacket references and Raw Water vs. Fresh Water Cooling.

My PO happened to post here under SMosher. That was one hell of a discovery.

In a way the bypass valve is simply a manual thermostat without any temperature sensitivity. It can augment your thermostats water blocking or flow function or it can be serve the block to manifold water directing function exclusively in the absence of a thermometer. The valve can provide some benefits when winterizing because you can force flow through the block and manifold, knowing that you have a well pickled engine. Good luck.
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Old 04-01-2021, 01:24 PM
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Quote:
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Context. I considered myself a redshirt freshman last year owning my first A4 since August.
*Much* better than being a redshirted ensign. (for the Trekkies out there )
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Old 04-01-2021, 03:36 PM
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Smile Yes...I am still alive and my A4 is too....

Very soon to unpickle my engine and reconnect batteries that I have been conditioning all winter like a mother hen watching her eggs.
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