Tweet
At launch last year, while still on the slip and prior to heading to my mooring, I heard a clicking from my late model A4 while at idle. I could not identify the source, and I was preoccupied with my time on the slip with flushing, back flushing and acid flushing the engine. The previous (and my first) season with the boat, I had repeated overheating issues from obstructions in the cooling system and I was trying to avoid any repeats there.
Under load, the engine lacked power and after about 5 minutes, the RPMs would begin to cycle for another ten minutes and then the engine would shutdown. And I could not get it started again.
I would (much) later discover that the plugs were fouled.
With the assistance of a dedicated friend, quite savvy with auto engines, we pulled the valve cover and identified that the #2 intake valve was sticking. We bathed it in MMO, checked and re-checked the valve springs and their settings. Then we observed the valves operating as they should while manually turning the fly wheel. And with the valve cover still removed (which is likely not recommended and rather messy), I ran the engine and observed the valves operating as they should for a minute or so before the #2 intake would again hang up, RPMs begin to cycle and would eventually shut down due to fouled plugs.
From this forum, I learned that historically, intake valves on the A4 stick due to elevated back pressure. I ran the engine with the exhaust flange removed. In addition to being noisy, also very dirty and smelly, so do so only with caution and plenty of ventilation. With exhaust flange disconnected from the manifold, engine runs much stronger. Symptom = elevated back pressure in the exhaust. SO, I pulled apart the exhaust system and could not discover any reason obstructions or any other reason why there might be elevated back pressure. No, I do not have Moyer’s gauge on the exhaust flange for measuring back pressure (in hindsight, it would have come in handy).
Somewhere in here, I learned from this invaluable forum that if the A4 has fuel, spark and compression, that is HAS to run. So, I chase my tail for a while to verify that I have both good fuel and good spark (I have a unique talent for turning a diagnostic test that should take an hour into an all-day event).
That leaves compression. I did not know how to run a compression test, which is not hard just that I am not very bright . My buddy shows up and runs the test in all of 5 minutes.
Here were my numbers:
Dry Wet
1. 35 50
2. 30 45
3. 115 didn’t record it
4. 120 didn’t record it
OK – so poor compression numbers for #1 and #2. Well, that seems logical, because I know I have a sticky intake on #2, so maybe that is affecting my compression numbers for #1 and #2. Also, when I pull my plugs, it is clear that #3 and #4 are fouled with excess carbon and #1 and #2 looked like they are just along for the ride (which basically they are – and I had checked this by pulling the plug wires on #1 and #2 without any noticeable change in engine performance).
So, many of you are likely saying – “Pull the head!” Well, I did not know how to do that and the prospect was too intimidating. I was certain I would break studs or do something else to make a bad situation even worse.
So, I start looking for a local marine mechanic to assist me - I was feeling guilty because I had already imposed far too much on my buddy, but now he was getting frustrated as well. This is what I heard from the few marine mechanics I could find in the area to even return my calls:
1. “Never heard of anyone actually running the A4 anymore. You need to re-power…”
2. “I have never actually worked on one. I will take a look at it but first we need to pull it from your boat…”
3. The local yard had already burned me once by giving me an “official” estimate for work that was twice the value of their previous “unofficial” estimate, so I had no way of knowing what that would eventually cost me – likely more than I had to spend.
Repowering was not a financially viable option - the fate of my boat rested in our ability to solve this problem and my buddy and I were not going to get any help locally.
Moyer to the rescue!
Knowing that I was intimidated by pulling the head, Don advised me that it was time to do some pressure testing of the block and manifold. And to my “disappointment” and continued frustration, they both passed the pressure test. At this point, I just wanted to diagnose some cause for my problem and then transition into solution mode. While $350 for a new manifold might not sound very appealing, it was far preferable to a rebuild or repowering.
No further diagnostics left to do, it was time to pull the head. And the season had slipped away, so we were going to undertake this while back in the yard on the hard. We had been hitting the studs on the head with penetrant for weeks, so the head nuts came off without incident. But I still could not remove the head from the block – it was stuck on there and I did not know how much to force it. We eventually got it off, but in the process, we basically destroyed the head gasket beyond any ability to evaluate its integrity prior to removal of the head. I had hoped to find a cracked intake valve on #2, maybe even #1 as well. Nope – valves were covered with carbon but otherwise seemed fully intact. I was despondent that there were no obvious issues (not obvious to me anyway) but I took some photos and sent them to Don.
Don immediately identified my problem from my photos. He could identify the old “paper” head gasket from my photos and stated that he had not seen one in more than a decade, as he had presumed they had all since failed. Don explained that back in the 90s, these gaskets were failing throughout the A4 fleet and subsequently causing widespread doubt about the long-term viability of the A4. Then, the new steel reinforced graphite head gaskets came along and squelched the panic.
Well, I knew none of this, but Don told me to install the new head gaskets (comes in a set of 2, so install both of them). I followed the steps in the Moyer Marine manual which explains everything in simple, cookbook style – if I can do it, then anyone can. So, with the new head gaskets installed, it was the dead of winter and so we bathe the cylinders, valves, and springs in MMO and then I cross my fingers and wait for Spring to see if we have solved the problem.
Upon launch this season, here are my new compression numbers:
Dry Wet
1. 90 100
2. 95 100
3. 95 100
4. 95 105
I have about 3 hours on the engine thus far. I have Raw Water Cooling aboard, and Lake Champlain is still very cold (low 50s) so she has not yet warmed up much, even at cruising speed. While I am reluctant to declare victory here, she has been strong under load and I have yet to foul a set of plugs. I am now hopeful.
Apologies for the long post – but I needed to express my appreciation to Don and this forum. Likely another boat saved from the scrap heap. For all the newbies (and I will likely always be a newbie when it comes to my A4), get the Moyer Manual and crawl around, over and under your engine. Everything you need to know is either in that manual or on this forum - and you will soon know at least as much and likely more than the so-called “experts” in your area.
Fair winds and following seas!
Under load, the engine lacked power and after about 5 minutes, the RPMs would begin to cycle for another ten minutes and then the engine would shutdown. And I could not get it started again.
I would (much) later discover that the plugs were fouled.
With the assistance of a dedicated friend, quite savvy with auto engines, we pulled the valve cover and identified that the #2 intake valve was sticking. We bathed it in MMO, checked and re-checked the valve springs and their settings. Then we observed the valves operating as they should while manually turning the fly wheel. And with the valve cover still removed (which is likely not recommended and rather messy), I ran the engine and observed the valves operating as they should for a minute or so before the #2 intake would again hang up, RPMs begin to cycle and would eventually shut down due to fouled plugs.
From this forum, I learned that historically, intake valves on the A4 stick due to elevated back pressure. I ran the engine with the exhaust flange removed. In addition to being noisy, also very dirty and smelly, so do so only with caution and plenty of ventilation. With exhaust flange disconnected from the manifold, engine runs much stronger. Symptom = elevated back pressure in the exhaust. SO, I pulled apart the exhaust system and could not discover any reason obstructions or any other reason why there might be elevated back pressure. No, I do not have Moyer’s gauge on the exhaust flange for measuring back pressure (in hindsight, it would have come in handy).
Somewhere in here, I learned from this invaluable forum that if the A4 has fuel, spark and compression, that is HAS to run. So, I chase my tail for a while to verify that I have both good fuel and good spark (I have a unique talent for turning a diagnostic test that should take an hour into an all-day event).
That leaves compression. I did not know how to run a compression test, which is not hard just that I am not very bright . My buddy shows up and runs the test in all of 5 minutes.
Here were my numbers:
Dry Wet
1. 35 50
2. 30 45
3. 115 didn’t record it
4. 120 didn’t record it
OK – so poor compression numbers for #1 and #2. Well, that seems logical, because I know I have a sticky intake on #2, so maybe that is affecting my compression numbers for #1 and #2. Also, when I pull my plugs, it is clear that #3 and #4 are fouled with excess carbon and #1 and #2 looked like they are just along for the ride (which basically they are – and I had checked this by pulling the plug wires on #1 and #2 without any noticeable change in engine performance).
So, many of you are likely saying – “Pull the head!” Well, I did not know how to do that and the prospect was too intimidating. I was certain I would break studs or do something else to make a bad situation even worse.
So, I start looking for a local marine mechanic to assist me - I was feeling guilty because I had already imposed far too much on my buddy, but now he was getting frustrated as well. This is what I heard from the few marine mechanics I could find in the area to even return my calls:
1. “Never heard of anyone actually running the A4 anymore. You need to re-power…”
2. “I have never actually worked on one. I will take a look at it but first we need to pull it from your boat…”
3. The local yard had already burned me once by giving me an “official” estimate for work that was twice the value of their previous “unofficial” estimate, so I had no way of knowing what that would eventually cost me – likely more than I had to spend.
Repowering was not a financially viable option - the fate of my boat rested in our ability to solve this problem and my buddy and I were not going to get any help locally.
Moyer to the rescue!
Knowing that I was intimidated by pulling the head, Don advised me that it was time to do some pressure testing of the block and manifold. And to my “disappointment” and continued frustration, they both passed the pressure test. At this point, I just wanted to diagnose some cause for my problem and then transition into solution mode. While $350 for a new manifold might not sound very appealing, it was far preferable to a rebuild or repowering.
No further diagnostics left to do, it was time to pull the head. And the season had slipped away, so we were going to undertake this while back in the yard on the hard. We had been hitting the studs on the head with penetrant for weeks, so the head nuts came off without incident. But I still could not remove the head from the block – it was stuck on there and I did not know how much to force it. We eventually got it off, but in the process, we basically destroyed the head gasket beyond any ability to evaluate its integrity prior to removal of the head. I had hoped to find a cracked intake valve on #2, maybe even #1 as well. Nope – valves were covered with carbon but otherwise seemed fully intact. I was despondent that there were no obvious issues (not obvious to me anyway) but I took some photos and sent them to Don.
Don immediately identified my problem from my photos. He could identify the old “paper” head gasket from my photos and stated that he had not seen one in more than a decade, as he had presumed they had all since failed. Don explained that back in the 90s, these gaskets were failing throughout the A4 fleet and subsequently causing widespread doubt about the long-term viability of the A4. Then, the new steel reinforced graphite head gaskets came along and squelched the panic.
Well, I knew none of this, but Don told me to install the new head gaskets (comes in a set of 2, so install both of them). I followed the steps in the Moyer Marine manual which explains everything in simple, cookbook style – if I can do it, then anyone can. So, with the new head gaskets installed, it was the dead of winter and so we bathe the cylinders, valves, and springs in MMO and then I cross my fingers and wait for Spring to see if we have solved the problem.
Upon launch this season, here are my new compression numbers:
Dry Wet
1. 90 100
2. 95 100
3. 95 100
4. 95 105
I have about 3 hours on the engine thus far. I have Raw Water Cooling aboard, and Lake Champlain is still very cold (low 50s) so she has not yet warmed up much, even at cruising speed. While I am reluctant to declare victory here, she has been strong under load and I have yet to foul a set of plugs. I am now hopeful.
Apologies for the long post – but I needed to express my appreciation to Don and this forum. Likely another boat saved from the scrap heap. For all the newbies (and I will likely always be a newbie when it comes to my A4), get the Moyer Manual and crawl around, over and under your engine. Everything you need to know is either in that manual or on this forum - and you will soon know at least as much and likely more than the so-called “experts” in your area.
Fair winds and following seas!
Comment