1997 Mercruiser 5.7 Overheat / Coolant Coverflow Issue

[jackalu]

would a head gasket really lead to that drastically low compression on one cylinder only? How do the other numbers look to everyone? and the plugs? I noticed oil on several of the plugs (both banks)....

 

[Grub54891]

I think a keakdown test would verify if the rings are bad or just the valves. Pull the heads,check the deck.If its just the valves,and headgaskets,easy enough to have the heads redone. No pulling the motor.

 

[jackalu]

I suppose first thing to do would be a wet test to determine if it is a bottom or top end issue? I don't have access to air where I am so a leak down test isn't possible. What is the possibility that it is a cracked block that is causing the original issue of coolant over pressurizing? How often do you see cracked blocks on these engines?

I am pretty new to working on V type motors; have worked almost exclusively on 4 cyl VWs and have pulled heads before. Pulling the heads on this thing looks pretty simple, is there anything I need to do from a timing perspective when I pull the heads and reinstall?

As always your guys help is greatly appreciated.

 

[tpenfield]

would a head gasket really lead to that drastically low compression on one cylinder only? How do the other numbers look to everyone? and the plugs? I noticed oil on several of the plugs (both banks)....

Yes, if the head gasket void is at the #6 cylinder and leads to a water channel, it would explain both the coolant overflow and the low compression on #6. The more testing you do, the better off you will be in determining the issue and proper fix. Time to focus . . .

 

[Ostsideend]

You should find water in #6 if this is the cylinder causing the problem.
Compare the spark plug to the others. It should show smaller pearls on it.



Good luck!
Oliver

EDIT: The view right onto the front of the spark plug will give hopefully some ideas. From side view it looks unremakable to me.

 

[jackalu]

I couldn't noticeably see any water on the sparkplug, but definitely some oil. I am going to do a wet compression test on the motor (all cylinders) and see if I am looking at top end issues or bottom end. I will report back here; if it looks like top end I will pull both heads and inspect block/pistons for damage, as well as headgasket (specifically for failure around a water jacket as this would confirm the coolant overflow issue). If all looks good with the bottom end I will take the heads in to be rebuilt and pressure tested, purchase a gasket kit and reassemble.

Any other suggestions/comments on my approach here?

Also, with regards to removing heads, can someone confirm basic procedure:

1. Drain engine of coolant and oil
2. Remove intake manifold
3. Remove exhaust manifolds
4. Remove valve covers
5. Loosen off rocker arms (can I leave assembled? Just loosened?)
6. Remove head bolts
7. Remove head

***Nothing needs to be done timing wise with the heads prior to pulling them, correct?***

 

[tpenfield]

You could do a leak test on #6 if you have a source for compressed air. You could do it at TDC to see if you have a top-end leak and then you could do it at BTC and loosen the rocker arms to see if possibly you have a cylinder wall crack, as was suggested.

After that, you would be at a stage to tear the heads off. Your procedure looks about right, but you will probably want to have the maintenance manual handy for reference, etc. Your valve timing is from the camshaft . . . if you only touch the top-end, then you will only need to worry about getting the distributor timing back correctly (distributor will come out before the intake manifold can come out)

As a general rule, you need to post pictures once you start to take things apart

 

[alldodge]

I couldn't noticeably see any water on the sparkplug, but definitely some oil. I am going to do a wet compression test on the motor (all cylinders) and see if I am looking at top end issues or bottom end. I will report back here; if it looks like top end I will pull both heads and inspect block/pistons for damage, as well as headgasket (specifically for failure around a water jacket as this would confirm the coolant overflow issue). If all looks good with the bottom end I will take the heads in to be rebuilt and pressure tested, purchase a gasket kit and reassemble.

Any other suggestions/comments on my approach here?

Also, with regards to removing heads, can someone confirm basic procedure:

1. Drain engine of coolant and oil
2. Remove intake manifold
3. Remove exhaust manifolds
4. Remove valve covers
5. Loosen off rocker arms (can I leave assembled? Just loosened?)
6. Remove head bolts
7. Remove head

***Nothing needs to be done timing wise with the heads prior to pulling them, correct?***

Need to remove your distributer to get the intake off. Put engine on No 1 TDC and mark distributer location before pulling distributer,

Just loosen rockers is fine no need to remove them

Will need to reset timing when put back together.

 

[jackalu]

Quick update here for everyone, to hopefully close the loop for those with similar issues.:

- pulled both heads visually blown head gasket between middle cylinders on both sides (should bring up compression there to an acceptable level), but couldn't obviously see a leak a cooling jacket... fingers crossed surrounding that.
- took heads in for resurfacing and pressure checks. Found that it was a bent valve in the cylinder with 0 compression! Replaced valve although couldn't really find the reason for the bent valve (it was suggested it was probably just due to an overheat and it getting stuck in a guide?). I did check the lifters for damage (cam lobe issue etc) and could see anything. Pushrods look fine to me, but I am no expert.
- took the time to visually inspect all the risers and manifolds - risers looked bad, found a set of stainless risers for $300 and they are mint!... manifolds I think are OK will post some pics of mating surfaces soon.

so I have it mostly together, just putting finishing touches on everything then I will sea trial and let you guys know. Hoping that between the valve and the headgasket I should have everything all sorted.

Keep you guys posted, thanks for your wisdom through this whole ordeal.

BJ

 

[jackalu]

As promised here are some pictures of the manifold mating surfaces (freshly sandblasted and painted!):

MANIFOLDS: https://drive.google.com/file/d/0B1Q9WJpTJdJlQ1pfdl85M0ZfT2M/view?usp=sharing
SURFACE 1: https://drive.google.com/file/d/0B1Q9WJpTJdJlUWtnOFVXdW5JR1k/view?usp=sharing
SURFACE 2: https://drive.google.com/file/d/0B1Q9WJpTJdJlT1ZwbjRZb3NmOWs/view?usp=sharing

And, for fun, one of my sandblasted and painted HE: https://drive.google.com/file/d/0B1Q9WJpTJdJlOXRFcFVQNnJ5WkU/view?usp=sharing

Let me know your guys thoughts on the manifolds. Also, I bought some high temperature permatex, was thinking of adding to the riser to manifold gasket, thoughts?

BJ

 

[alldodge]

A fresh coat of paint can hind a whole bunch of stuff. Did you acetone test after they were sand blasted?

Need to smooth out the surfaces on the manifold mating surfaces. Those pits can cause some issues Using sealant to fill in the pits will work but smooth is better. Could pull the plugs a use a large flat file.

 

[Bondo]

Let me know your guys thoughts on the manifolds. Also, I bought some high temperature permatex, was thinking of adding to the riser to manifold gasket, thoughts?

Ayuh,.... I'm with AllDodge,.... File 'em good 'n Flat, no glue should be necessary,....

I use the Merc carbon/ graphite gaskets, dry,....

 

[jackalu]

Thanks guys, I filled them up with water and let them sit overnight.... no drop in level/no leaks. I will test with acetone prior to running them and will file the mating surfaces down. They look pretty meaty still to me.... rule of thumb is it should be 1/4" between jacket and exhaust outlet at flange correct? Presuming so, should be alright I think.

 

[jackalu]

Another update here, motor has been reassembled and I started it and set base timing. Deffniitely running smoother now, haven't done compression check but pretty certain all will be well. No coolant pressure build up obvious on the muffs, but the real test will be dropping it in and running under load. Here are some pics of the transformation from old and rusted to new and shiny:

OLD - https://drive.google.com/file/d/0B1Q9WJpTJdJlLVFlbWNHdFZWeDA/view?usp=sharing

NEW - https://drive.google.com/file/d/0B1Q9WJpTJdJlQUM3ZEtTaWk5ZWc/view?usp=sharing

Hopefully I will have one last post confirming all is well with the sea test this upcoming weekend and thread can be closed.

 

[Speakrdude]

What? You cant test tonight??? Come on man!

 

[tpenfield]

Sure looks a bit different and much improved. :thumb: Hopefully it will test out well.

 

[jackalu]

Great news! Tested the boat in the water, runs fantastic, no coolant pressurization and temperature is rock solid at 175 (still need to hit it with my IR gun to make sure its accurate but should be fine).

To summarize, the issue was a bent valve and a blown head gasket. To my surprise, all of the work wasn't particularly difficult just time consuming...

I have a few other completely unrelated issues that I am chasing down on the boat as well, but I will start new threads for those issues to keep things cleaner for the site.

Thanks everyone for the help, BJ