Water on top of Intake Manifold

[Rivergator]

After several years of restoring my 1988 Sylvan bow rider, Saturday finally came the big moment of truth. After some earlier preliminary quick dry starts to see if the 4.3 ltr engine actually fires up, which it did, Saturday was the day to see if it actually runs normally for at least 1/2 hour. I hooked up the water supply (see picture 1) and started her up. I expected it not to be perfect and some touch ups needed to be done, but that 1/2 hour gave me enough time to set the timing, adjust the idle mixture screw and check all of its vital signs of being alive and hopefully well. It all actually came out pretty darn good, I must say. Some smaller shortcomings need to be taken care of but that's beside the point for right now. But to my disappointment, about 20 minutes in to the run I discovered about a teaspoon worth of water on top of the intake manifold where bolt #7 is (see picture 2). Now that was not good. I stopped the water, turned off the engine and took a deep breath. A few minutes later I checked the oil to see if I had water in the oil or if it was milky. Oil was clean and pure. I called it a day, I need to do some thinking. This Sunday morning I pulled the plugs on cylinder #3 and 5 wondering if water also dripped into the cylinder and would cause a hydro-lock. I cranked the engine and it cranked just fine expecting to see moisture coming from either one or both cylinders, but nothing. They were nice and dry. I put a piece of paper in front of the spark plug holes to catch any squirts, but the paper was dry. Can anybody tell me what has happened here? I looked in the manual to recheck if I did something wrong when I put the engine back together, but I didn't see anything I might have overlooked. Now, I have seen some engines maybe even the GM 4.3 ltr engine (I think one of the studs holding the water pump) where a stud will actually go through the wall in to the water passage and must be installed with a sealant. The manual doesn't say anything that the intake manifold bolts must be embedded in sealant. Does anybody have an idea what is going on here. Should the intake manifold bolts have sealant on them?

 

[Lou C]

That appears to be right by the water passage part of the gasket. Even though the only place the water flows thru the intake from the heads is in the front, those passages are there in the heads because the head is really just one casting the same for the port & starboard sides. That passage is blocked off at the rear of the intake manifold. Try carefully re-torquing the bolts to 30-35 ft lbs; (yours looks like a pre Vortec) the gasket may have takes a set & not sealed 100%. You can use sealer on those bolts not for water because the gasket takes care of that but for oil, sometimes oil will come up those bolts and appear on the intake.

 

[flashback]

I had water dripping out of the lower shift cable at the shift plate. Water was getting past the o ring in the drive and forced into the cable when running..

 

[QBhoy]

Not sure..but if you pressurised the system with too much pressure off the hose…with the engine not running…no exhaust pressure is present. Can rarely allow water ingress. Perhaps not the issue though. Any sign of water that might have came or dripped from the underside of the engine cover or hatch ?

 

[stresspoint]

it could be a cracked intake manifold.

 

[Bondo]

where a stud will actually go through the wall in to the water passage and must be installed with a sealant.

Ayuh,..... Take that bolt out, 'n see if it's a blind hole, or through hole,....
If it is a through hole, slather some perfect seal on it, 'n put it back in,....

 

[Rivergator]

Alright, all good pointers and suggestions. I will get to it asap and report back

 

[Lou C]

Those manifold bolts thread right into the cyl head but not sure of any thread into a water passage. Thinking back I had the same issue…I had to remove that engine lift bracket that some OMCs and Volvos had using the last 2 Intake bolts on the port side. I had tried a Holley carb instead of the old QJet & had to fab up a custom bracket for the throttle linkage. When I removed those bolts a bit of water did seep out. However it stopped as soon as I installed the bolts & torqued em up.

 

[stresspoint]

from memory ?? , the only ways water can get to the manifold bolt is bypassing the gasket, usually can be sorted by tightening the bolts again after warm up.
i have seen this when a manifold cracked ,replacement manifold is the only fix there.
also when there has been excessive rust around the water ports they can seep water across , iv fixed this successfully many times over the years on SB chev and Holden V8 alloy manifolds with belzona .

 

[tank1949]

After several years of restoring my 1988 Sylvan bow rider, Saturday finally came the big moment of truth. After some earlier preliminary quick dry starts to see if the 4.3 ltr engine actually fires up, which it did, Saturday was the day to see if it actually runs normally for at least 1/2 hour. I hooked up the water supply (see picture 1) and started her up. I expected it not to be perfect and some touch ups needed to be done, but that 1/2 hour gave me enough time to set the timing, adjust the idle mixture screw and check all of its vital signs of being alive and hopefully well. It all actually came out pretty darn good, I must say. Some smaller shortcomings need to be taken care of but that's beside the point for right now. But to my disappointment, about 20 minutes in to the run I discovered about a teaspoon worth of water on top of the intake manifold where bolt #7 is (see picture 2). Now that was not good. I stopped the water, turned off the engine and took a deep breath. A few minutes later I checked the oil to see if I had water in the oil or if it was milky. Oil was clean and pure. I called it a day, I need to do some thinking. This Sunday morning I pulled the plugs on cylinder #3 and 5 wondering if water also dripped into the cylinder and would cause a hydro-lock. I cranked the engine and it cranked just fine expecting to see moisture coming from either one or both cylinders, but nothing. They were nice and dry. I put a piece of paper in front of the spark plug holes to catch any squirts, but the paper was dry. Can anybody tell me what has happened here? I looked in the manual to recheck if I did something wrong when I put the engine back together, but I didn't see anything I might have overlooked. Now, I have seen some engines maybe even the GM 4.3 ltr engine (I think one of the studs holding the water pump) where a stud will actually go through the wall in to the water passage and must be installed with a sealant. The manual doesn't say anything that the intake manifold bolts must be embedded in sealant. Does anybody have an idea what is going on here. Should the intake manifold bolts have sealant on them?

NOt real sure!!! I had an engine compartment deck leak where two MC were mounted in boat. Water dripped down carb into block. I almost pulled motor, but then noticed a small amount of rust on carb..

 

[Lou C]

While water can drip down from the engine cover on to any part of the engine; if the gasket doesn’t seal or the bolts not torqued 100% you will see a leak on one of the 4 corners of the intake. Remember the rear ones are closed in the intake but open on the cyl heads. Front is open on both, water flows thru the block up thru the heads & out the front water passages in the intake to the thermostat housing.

 

[Scott06]

Alright, all good pointers and suggestions. I will get to it asap and report back

check the oil for water if you think the intake gaskets are leaking.

Possible it came down from the hatch cover depending on design .

 

[Bt Doctur]

And if a vortec 8 bolt manifold the torque is 13-14 lbs

 

[Rivergator]

I am noting all of these good tips here and I will get back to the boat on the weekend to do some testing and follow your suggestions. But I have some answers already. It's not a Vortec, no water in oil, no hatch or cover or other external source where water could come from, waterhose was turned on 1/2 turn to prevent pressurizing, I think it was rather underpressured judged by the temp of the headers, engine didn't even get to 150 F yet, but with all your good suggestions I will have my work cut out and I will report back. Thank's y'all

 

[Rivergator]

I went about it systematically to see what was going on. Since I am restoring the boat and everything connected to it, I looked up my documentation to see what I did when I did it and all the intake manifold bolts were treated with sealant at the time as well as the manifold gasket and torqued to 40 lb/ft. So I figured I am not going to mess with the bolt right now but run the engine again and watch to see if I can see where the water comes from. Then I noticed a tiny spot of water closer to the carburetor which was strange because we haven't had any rain in over a week. The morning dew is there and the boat is under a tent, so I started the engine and ran it for a good 45 minutes and I am happy and relieved to say that there were no leaks anywhere. I will leave it at that. Probably some water leaked through the tarp/canvas like many of you suggested. Thanks again for all your help