Hello,


Looking for a little insight into coolant loss on 5.7 1988 Crusaders FWC.

Last summer my RH engine overheat alarm went off and shut down engine. After refilling coolant, I notice a slow loss of coolant. About 2 QTs every 4 hours of running. I just kept topping off so as not to run out of coolant and really overheat the enging. At the same time I replaced the heat exchanger but coolant loss continued. Then pulled all the plugs and #6 plug was very white (steam cleaned?) compared to others. I also observed bubbles in the heat exchanger while engine was running. So I'm thinking that I have a bad head gasket around the #6 cylinder. Of course this engine is the stronger of the two engines. Unknown hours and has had at least 1 rebuild. Elbows and riser were replaced last season, but did not change exhuast manifolds. During tear down there was no signs of milk shake oil under valve covers.

Last week I did a compression check on all cylinders and thought that the engine was worthy of a new head gasket and maybe rebuilt cylinder head.

1. 174 psi 2. 183 psi
3. 176 psi 4. 180 psi
5. 175 psi 6. 185 psi
7. 183 psi 8. 175 psi

After tearing down the engine I was hoping for the smoking gun of hole in the head gasket around #6 Cylinder but did not find it. I did not observe a hole in either head gasket (LH/RH cylinder heads). While also looking at intake manifold gasket I did not observe any hole or tell tale water stain trails.

1. #6 Cylinder has highest compression, (is this related to water not compressing?)
2. Should I see tell tale trails of water stains?
3. #8 Cylinder wall has staining similiar to water stains (not rusty, but discoloring of cylinder wall)
4.Could gasket be faulty without a noticable hole?
5. Some intake and exhaust valves bottoms are soot covered. Some are not and look pitted. Both LH/RH cylinder valves have this condition. Could both manifolds been bad?

Stumped,

Timmy

Your leak was at the intake gasket. Was the intake gasket a plastic unit with silicon rings on it? These were used on the vortec style 4 bolt intake systems, and are a very common problem. When reinstalling, they only tighten to 9 ft. lbs. or so.

A head gasket leak to a water passage will blow all the water out of the cooling system in short order. You only have maybe 14# pressure in a closed cooling system, and 2000# of compression pressure in the cylinder. Water doesn't leak into the cylinder except when the engine is shut off.

Bill,

The intake gasket was plastic with blue silicon rings surrounding the intake ports. Is this a vortec gasket? Being a pre vortec motor the intake manifold is a 12 bolt version. The motor also has center bolt valve covers vice the earlier motors that had the bolts on the edge of the valve cover.

With the coolant in the heat exchanger bubbling/burping and #6 spark plug very white, would this be caused by the faulty/incorrect intake gasket?


Timmy

That's the same style intake gasket that causes problems on the true vortec engines. They did use a non-vortec cylinder head that used the center hold-down screws on the valve cover.

I'd first suspect this intake gasket because they are known to be problems. Next, I'd CAREFULLY inspect the head for cracks around the valve seats and pockets. As you found, a head gasket problem is unlikely. Cranking compression of 180# won't show up a possible leak, but 2000# of pressure when the plug fires will. However, you appear to have water at maybe 15# leaking INTO the cylinder. This can only come from water entering on the intake section of the engine. A white valve can also be caused by running lean.

The "bubbling" is an interesting aspect. I really suspect it is unrelated to an engine compression leak, though. They make test kits to determine the presence of CO (carbon monoxide) in the coolant. Since CO only comes from a by-product of combustion, this is a good test.

Keep me posted............

It's early and I just had a thought, not all that familiar with the SBC but I heard somewhere that you had to put sealant on (one?) of the head bolts on these motors? Just tossing this one on the table, not sure it really has any relevance to this issue. I understand how the intake could be leaking some coolant, but don't understand how it could be creating leakage into the closed cooling system causing bubbles.

Tom

I was wondering about the sealant on the head bolts myself. All the bolts should get RTV. The best thing would have been to put an radiator pressure tester, STANT or similar, on the heat exchanger and run the engine, if combustion pressure is escaping into a cooling jacket the gauge will build pressure. Of course the engine is apart now so magnufluxing the heads is your best angle. The manifolds could be rusted through causing the cylinder wall staining, etc. Is this boat in salt or fresh water? When you put it back together you can't beat FELPRO marine gaskets.

Greg

Water wouldn't enter the combustion chamber by leaking past the head bolt threads. They are surrounded by the head gasket. @ of the 3 rows are under the valve cover..water would get into the crankcase.

Excellent, Bill,

Thanks for the critical analysis. I remembered something about the head bolts on the SBC but since I'm a Ford guy and don't have much experience, and precious little RECENT experince with the SBC, I appreciate your setting the record straight. I would hate to contribute to bad info that someone would take to heart.

Tom

Timmy,

You stated the manifolds had not been replaced but the risers have been. Your engine is probably plumbed to cool the manifolds with the closed loop antifreeze/water. The risers are cooled with raw water. There should be a SS block off plate and gaskets blocking the water passages between the riser and the manifold. A leak here can cause part of your problem, or the bubbles in the heat exchanger could be combustion pressure leaking into water jacket, ie crack, or what if there is a rust hole in the exhaust manifold between the exhaust passage and a closed cooling passage. Exhaust could push into the cooling system/heat exchanger with the cap off, causing the air bubbles. Inspect those manifolds and riser gaskets!

Greg

Latest update:

1. Took cylinder heads and head gaskets to machine shop and the professional machinist (unlike me) looked at them and very quickly pointed out 3 areas the gaskets were leaking at.

2. On both LH/RH sides between cylinders 4/6 and 3/5 (middle cylinders). He also pointed out an area that was close to a cooling jacket hole and a cylinder. When I was looking for a leaky gasket I assumed (yes I know) that I would have a big hole and the areas that showed leakage were shinny as apposed to brass colored coating that had not been worn away. The gasket was physically intact but with shinng spots around the bronze/bronze colored areas. I will try and post pictures later on.

3. The shop was going to go over both heads and should let me know this week the overall status by Friday.


Thx for all the reply's and I will keep you updated,

Timmy

The signs can often be very subtle. If it was leaking, the question is why?? Was this engine severely overheated? If it was the head gasket leaking in numerous places, a very careful check of the mating surfaces should be performed.

My experience is..SBC head gaskets are pretty much bulletproof.

Don't assume (y'know..wink wink) that you've found the problem yet.

No all head bolts should get sealant none of them should get RTV. All bolts get thread sealant head bolts go through water jackets so the first half inch of threads get sealant. In particular use ARP thread sealant or Loctite they are the best there is. I did not use RTV silicone I used Loctite and I like it, it doesn't impede your torque readings and it is made for the job at hand. I would think the ARP stuff is better but I couldn't find it at the time I have since learned where to buy it. RTV is not the stuff you want to use when reassembling an engine I like to use the actual gaskets and/or recommended sealants it is the only way to go if possible and it usually is possible call Robert Henkel at http://www.chris-craft-parts.com or Dan Cook he ran the old Chris Craft engine shop in Gallipolis Ohio or Bruce at lakeland marine and auto in Port Clinton Ohio they can find the gaskets parts etc that you need.

What is wrong with using RTV to seal the head bolts that go into the water jacket? Is permatex Gasket sealant suitable? (#2 Form.a.Gasket/sealant) I already have a set of Felpro marine gaskets from the machine shop that worked on the heads. Just waiting for a couple hours of free time to start reassembling the engine.


Timmy

I've been using RTV or #2 Perm for 30 years. That is news to me. I guess we can't use vaseline on the rods and mains anymore either. We have to go BUY something more expensive.

"Before installation, put some sealer on the head bolt threads to stop water coming up at this point".

Photo shows sealer being applied to the first 5 threads at the end of the bolt.



Another page says "coat the first 1/4 inch of thread with silicone sealer to stop water coming up the threads"

The book is "HOW TO REBUILD YOUR SMALL BLOCK CHEVY", by David Vizard.

Roy

That is right Roy, that book and many other shop manuals prescribe RTV silicone (room temperature vulcanizing) for sealing head bolts at the first few threads. Don't get carried away with the sealer. Clean and thread chase the holes and it works just fine.

Greg

So what was the final verdict? What caused the head gaskets to leak, if that was the problem? Were they original gaskets or a cheap replacement?

My underlying concern is..head gaskets simply don't leak or fail anymore.

I do not know why the head gasket leaked. The machine shop had nothing specific besides blaming the enthaol gas. I guess if there was bad gas, the heads might of lifted up a bit during detonation and then started leaking. (That's what I was told, don't flame the messenger). The heads were machined down and magnafluxed. Just awaiting some free time to start the putting back together.

Alcohol actually has a relatively high effective octane rating.............

Make sure the block is flat..check it with a straightedge. Are the headbolts reuseable? Are they the type that tighten by a certain amount of twist AFTER an initial torque setting? It almost looks like the bolts weren't tight.