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Head gasket and knocking!

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mylillooker

mylillooker

Senior Member
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yes, I know the two don't really go together.

First, I'm going to be replacing the head gasket. Moss has two, one for $49 that it list as "Payen" brand and another for $28 that just say aftermarket both are what they call sets. There is also just a gasket for $16. Which one do I REALLY need? Also, how much time should I expect to spend doing this... first time and not extremely mechanical. I know I'll need to have it looked at when I get it off and possibly machined. But minus that, how much time?

Second, there is also a horrible knocking when under load. I'd like to call it bad, but I think it really leans toward horrible. I haven't started it since. What should I be looking for? Where should I start?

I have a Haynes manual that has served me well for simple fixes. Should I invest in something else for the new task at hand?

Help I'm falling apart!
/ubbthreads/images/graemlins/cryin.gifMario
 
I'd get the Payen brand. I had mine fail, and the Payen is reputed to be superior. The generic gasket is probably of lower quality, and it's not like it's really that expensive when you consider how long it should last.

As to the knocking, knocking under load could mean detonation (bad, but possibly easily cured -- may be a carburetion or spark issue) or (more likely, especially if you say it's borderline horrible) a connecting rod knock. Did it develop over time or occur suddenly? Does it occur on startup? If it happens on startup, it's likely a bearing failure of some kind, but more likely a rod bearing. In that case, I'd say pull the engine and have it looked at (or if you're not inclined to pull it yourself, any mechanic's shop should be able to do it fairly quickly).

Hope things go well ...

P.S. Why are you changing the head gasket? It may be that you should wait until the bottom end is checked out before bothering with the top half. Also, it may be time for a stock rebuild. These can be done fairly cheaply if you find a reputable shop and provide all the parts (they generally don't like to find them themselves). Moss usually offers decent rates, but some of the parts, like valves and guides, are available through 'the usual channels' for engine shops. My engine guy can also source bearings and custom pistons as required, but I generally provide the oil pump, gasket set, etc.
 
There is a distinct difference between spark knocking (pre-detonation) and a rod knock. Spark knocking occurs when the air fuel mixture in the cylinder ignites before the piston has travelled up far enough. The force of the explosion kinda "jerks" the piston and puts a huge load on it as it travels through it's stroke. This is usually caused by excessive residual heat in the cylinder or poor quality fuel. The excessive heat is most often caused by over advanced timing but may also be caused by carbon build up on in the combustion chamber. Plugs that are too hot will also cause this some times. A spark knock usually only occurs when the engine in loaded (like trying to climb a hill in high gear) and is more of a pinging sound than a knock. A rod knock occurs when a rod bearing has either worn out completely or has spun in the cap resulting in both halves of the bearing being on one side of the rod with the other half of the rod riding on the crank directly. This is very dangerous and usually results in the need for a new rod and a new crankshaft. A rod knock will happen at idle and at speed. Plus it is a deeper more gutteral knock. It is usually accompanied by a drastic change in oil pressure as well. If your oil pressure is normal and the knock only happens when you load the engine then it is probably a spark knock and simply lowering your timing a bit might help this. Hope this helps some, I'm sure someone will be along to provide more pieces to this puzzle for you soon.
JC
 
jcatnite said it all and in words that were very understandable. salute.
 
I'm changing the head gasket because of the gray foamy stuff in the engine. I believe it's water in my oil. The engine has never overheated.

As for the knocking, I was driving it home and was on the expressway and all of the sudden it started knocking something terrible. It didn't seem to knock as I coasted or in first gear. I went back the next day to check it out and have it towed. I started it up and there was no knocking ...revved up the engine, still no knocking. I drove it back to my apartment and almost there, it started knocking after turning a corner in third, but not so much in first or second.

Please feel free to ask any questions that might help diagnose the problems.

Thanks,
Mario
 
You've bit-by-bit provided new information that makes me think you've got some problems...lemme see if I understand:

you were driving down road & heard engine knocking under load...when oil checked, it was milky like water had gotten into oil...there was no smoke from exhaust at any time...engine doesn't knock until it gets warm

is that about right?

"knocking something terrible" under load is probably rod/piston knock caused by lack of lubrication

If so, you might want to look for a cracked head while you've got it off.....you might also want to look at your bearings/rods/pistons to see if any damage was done.
 
What has happened to your oil pressure (before and after)? FWIW, I had a pressure plate problem that sounded like a bottom end knock, but upon investigation I could tell it was in the bell housing area and not the bottom end.
 
Hmm, water does not compress like an air fuel mix. I think if he solves the water leak problem he will solve the knock problem as well. Must be head, or gasket or both. Anyway I would pull head and take to my favorate machine shop and let em check it out, ie valve seats, head level, cracks and if all checks ok grind valves while out.

Reassumble with new bipass rubber as well if you have.
 
Ok, didn't know about the water in the oil thing. Should have guessed when you were talking about replacing the head gasket. Water in the oil will look like a tannish almost whiteish milky goo that will collect on the non moving parts of the engine internals (Diptick, valve cover, etc.) A little water in the might not hurt as it could be caused by the engine "breathing" as it heats up and cools down on particularly humid days. A lot of water will emulsify the oil in your engine reducing its viscosity dramatically. Also, I've always heard but never personally confirmed that antifreeze is pure heck on your engine bearings. Something about the glycol preventing the oil from forming the lubricating oil wedge that we depend on to keep things from rubbing (think fluid friction instead of rubbing of the shaft directly on the bearings.) I guess my advice to you would be to drain the pan. Oil floats on top of water so you might get a little water out first. See what is going on in your engine. If you pull your head your going to have to do this anyway. When you pull your head, look for obvious breaks in the old gasket. If you can't find any, then you need to follow Tony's advice and have the head checked for cracks. You won't know for sure what is going on in there till you drain the fluids and see for yourself. Also, if you find any metal in the oil when you drain it this is a really bad sign. Bearing lining (babbitt) isn't magnetic so if there is a big question about bearing damage you can strain the oil through a cotton cloth and you can disect the oil filter to see what it has trapped. I've done it in the past. You are looking for slivers of silver material that has a hardness similar to lead (the primary component in bearing linings.)
 
Am I right in assuming that the head gasket definitely needs to be changed? While the head is off, is there anything I can do or that may need to be checked regarding the knocking?
 
check my post above for a start. By all means check and change oil.
 
[ QUOTE ]
While the head is off, is there anything I can do or that may need to be checked regarding the knocking?

[/ QUOTE ]
A quick and dirty check would be to rotate the crank and see if there is any noticeable lag, or slop, in one of the pistons traveling in the bore. This would be a sure indication of a spun bearing.
Personally, I'd just yank the engine now, and be done with it. It's much easier to work on while it's sitting on the engine stand.
Jeff
 
Pulling the engine is a piece of cake. I've done it several times in the past two weeks & you need no more than an hour tops. For me it helps to the have the head in place for pulling it out.
 
I have also found it easier to pull with the head in place.
 
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