Exhaust leak in cooling system, power loss?

[fvigeant]

Hi,

Here is my story...

I have a late model A4 that is raw ater cooled, the season prior (2008) we developed an overheating problem which I thought was due to a plugged raw water strainer as it was late in the season... this came to light in an initial event that was a bit scary becuase the engine severely overhead to the point of burning off excess fogging oil 200+ degrees (causing us to shut off the engine ASAP and briefly freak out at the possability of fire--- very unsettleing--- not to mention at the high temp the engine did not want to turn off even with teh key out.... why is that?). As I went about the engine compartment I found a fairly full strainer dumped it... let the engine cool for a couple hours and sailed slowly back to our mooring. After the night of cooling and the cleared strainer the engine got up and running no problem. Seemed like problm solved... I bought the MMI oil and temp alarm kit... needed some piece of mind...

Last season (2009), as I was opening up the engine with the usual MMO in teh cylinders etc. I got her to turn over but she ran real rough for about 15 seconds... scratchy metal sound... then a crazy bang... and I immediatly shut the engine off. Thinking i had just snapped a valve or something I petitioned the devine and we went at it one last time... started up and sounded fine. Odd.

Throughout the 2009 season I noticed an oil drip from where the circular plate attached to the prop shaft enters the reverse gear housinig box. I believe I have a direct drive 1:1... if it matters. Wast this teh cource of my bang???

Well this post is about cooling... all the above is connected to this issue... maybe...

So on my way to pull out the boat ending the 2009 season we got caught by the tide and wind and had to motor some 4 hours. About 1-2 hours in the heat alarm went off... thinking of the strainer i said easy fix... there was some crud so I dumped it... the boat started, temp dropped, along we went. As we approached the drawbridge with a 3kt exiting tide coming straight at us we needed to throttle up, again the alarm goes off... so we circle around... I dump the strainier and blow through the lines, check seacock for ample waterflow. Again start the engine, temp dropped and through the bridge we go... just through the bridge the alarm sounds... explatives as the temp rises and the current is trying to push us back into the now closed bridge. Our only hope is fighting the tide to an open slip at a marina up ahead, engine required current now 4kts. Thankfully we make it to the slip under power. Shut down engine and furiously thumb through my MMI rebiuld manual on board... we figure out we have a gummed up thermostat, cool... but no spare... after fiddeling around we decide to let the engine cool a bit and just remove the thermostat entirely for the last leg of our journey... this way water will just dump through the header and I can replace over the winter.

Everything appears fine, we start up and head up river... feels like a victory and an answer to the previous year's over heating... junk thermostat... maybe, maybe not...

We go about 1-2 miles up river and suddenly this steam engine sound emerges from the engine compartment and there appears to be somewhat a loss of power. I open the door to find a rythmic exhaust smelling steam powering out from an area beneath the thermostat cover (remember I removed my thermostat and did my best to crank down the housing with a pair of pliers to get us home). We had no choice but to keep on... was this the result of a missing thermostat like a bad gasket or an actual crack in the header?

My boat under power typically does 5.5 kts under full power with no wind. We we headed into 5 ft seas and 30 MPH winds. Under full power we had barely 1 kt on the GPS. After a few hours me had made enought progress to get out of the wind and the tide had become slack. We made it home but now my big question is...

Why do I have exhaust pressuring out of a space between my thermostat housing and the header, and why does this result ina loss of power? Did the crash bang at the begining of the season indicate somthing that woudl cause the oil leak or somthing that would cause exhaust to leak into the coolant chamber? HELP!

Just FYI at the begining of 2008 I tested pressure on all cylinders and they were up over 90psi and shes never had a rebiuld, I haven't tested since the crash bang but there was no detectable power loss until I removed the thermostat.

Thanks for any and all ideas!

[hanleyclifford]

if you have not already done so, check the impeller on your water pump. a thermostat is seldom solely responsible for overheating.

[fvigeant]

The impeller is fine, I replace it every season... the pump is an upgraded MMI unit. Water flow out is great but its hard to say where it goes in the engine. I don't use a bypass valve but if I clamp down to force water through side jacket there is no problem. In 2008 I did an acid flush also. Exhaust is newer (5-8 yrs old). I do get a little steam in the exhaust at times also tends to run rich (plugs get sooty) if that matters.

[hanleyclifford]

another cause of overheating is incorrect timing. first, make sure that your centrifugal advance is free and operable thru its correct range. next make sure timing is correct. both Universal and the Moyer manual have timing instructions, but i actually do it the old fashioned automotive way with a timing light. put a little white out or paint on the arrow on the flywheel housing. make sure the pin on the crankshaft is visible. TDC will be shown just like on a car engine, pin vertical on the arrow. find TDC at the lowest possible rpm; then work the throttle with one hand while observing the pin under light in relation to the arrow. i don't like to see more than 10 degrees of crankshaft advance all of which should occur before 1200 rpm. by the way, the distributor should be locked down on TDC at that lowest possible rpm.

[fvigeant]

I have been suspecting the timing needs adjustment. I know the old strobe and flywheel marking trick... where is the pin you are talking about... do you have a picture? I have an electronic ignition I haven't installed becuase i suspected the timing was a bit off. I think the electronic install requires the timing be set mechanically before converting over. Can this be done properly on the hard or should it be done in the water. In gear or neutral. Sorry I get teh concept of timing but have never attempted to set it for fear of causing damage to the valves.

[Marian Claire]

I think this is what HC is referring to. Dan S/V Marian Claire

[hanleyclifford]

the picture by MC shows the pin clearly thru the end of tghe crank just about horizontal. they call it a spring pin. i would hold off on the electronic ignition until the distributor issue is settled. timing can be set in or out of the water, but i like it best with the engine running. you need to eliminate the possibility that your centrifugal advance has gone amuck.

[hanleyclifford]

as a further clarification, the spring pin will be vertical and pointing to the keystone shaped mark just below the "E" in the word "Universal" when the engine is at TDC. sorry about the mix up. forget the flywheel.

[ArtJ]

With regard to insufficent speed under heavy conditions. Consider going
to a indigo propeller it should solve that problem.

with regard to engine cooling, you may want to follow Don's detailed
engine flushing procedure as a start. This is in the overhaul manual and
also posted on this website.

[hanleyclifford]

removal of thermostat

After studying your original posting it occured to me that after removing the thermostat after your bridge experience, one with which I am personally familiar, you may not have tightened the nuts enough when you put the housing back on. This would account for the exhaust leak under the housing, actually a compression leak. This however is not the original problem. That bang you described strongly suggests a timing problem, maybe even a really lose rotor or a broken advance weight spring leading to "floppy" timing. Sometimes even a distributor cap can develop tiny cracks which can cause "cross firing". I suggest that you take the distributor to your shop and study it carefully.

[Jesse Delanoy]

Incorrect timing can also cause the engine to continue running after the key is turned off ("dieseling").

I learned this on my first car, a 1971 Opel GT, not so very different from a larger version of the A-4.

[fvigeant]

Sorry for asking the obvious, but, when I am lining the pin up to the keystone on the front of the motor does it matter which side of the pin for TDC?

[hanleyclifford]

crankshaft springpin line up

Good question. It doesn't matter which end of the pin we consider because we are interested in pin deviation from the vertical. As the engine rotates counterclockwise viewing from the flywhel aft, when #1 fires on TDC the pin will be perfectly vertical when the strobe flashes. As rpm increases, you will observe the pin rotating clockwise under the strobe, advancing the spark. The centrifugal advance will be an educated guess unless you take the trouble to mark out some hashmarks on the flywheel housing. Just put the light on #1, get the rpm as low as possible, look at the pin under strobe and tighten the distributor where the pin is vertical. Don't worry about which end is which. Then with light on the pin hope to see a smooth advance on the crank of about ten to twelve degrees.

[ndutton]

HC's info is spot-on if you're running the engine and using a timing light.

If you're trying to set the engine by hand at TDC it certainly does matter which end of the pin you use and TDC is on every other revolution. Assuming the distributor is out and you can't use it as an indicator, you can peer into the spark plug hole of #1 and watch the intake valve as you're turning the engine. If the valve cover on the carburetor side of the engine is off you can watch the valve that way too. After that intake valve opens, as you continue to rotate the crank the next time the #1 piston reaches the top will be TDC and you can then put a dab of paint on the flywheel pin to identify the proper end.

[fvigeant]

so timing is not the issue though i did find one of the screws on the distrib loose...overheating seems to be a combo problem between a plugged water jacket and a head cover/ head gasket issue.... the saga will continue... hope to hit the water this year