'89 240sx, KA24E. 185,000 miles.
I'm starting to take everything apart now to rebuild what I thought was a bad headgasket. (prev. thread: http://www.nissaninfiniticlub....28282) Before I started, I did a compression test.
Results: 165-160-155-157.
I'm new to blown engines, but it follows that if the headgasket is blown, should not the compression be bad as well? Is this not close to the range compression should be, allowing for the amount of miles on the car? I'm wondering if my headgasket is actually blown, or if it could be a hole in the timing cover. There is coolant in my oil, but I've read this may also be caused by a hole in the timing cover. Thoughts?
-D
Blown engine (?), good compression?
I took another look at it and noticed something else. Along where the headgasket is there is a solid red material coming out. It is also present where some threaded holes are in the block. Pics are here:
http://www.pbase.com/peter_kuhn/engine
The texture is soft, spongy, and gummy. Is this something similar to thermalweld? I have a theory that the previous owner blew the engine, then went with the cheap fix, thus causing my decent compression results, but still not really fixing anything.
http://www.pbase.com/peter_kuhn/engine
The texture is soft, spongy, and gummy. Is this something similar to thermalweld? I have a theory that the previous owner blew the engine, then went with the cheap fix, thus causing my decent compression results, but still not really fixing anything.
That's RTV, a sealant that comes in a tube. Used to seal mating parts to keep the seams tight to fluids. Is that a bad casting, or is there a crack in the head (3rd pic) right below the rocker cover? You may have a crack in the head that is allowing coolant into the case. If it's low enough, it wouldn't necessarily affect your compression much I don't think. The engine noise might (hopefully) be due to the coolant in the oil, which is essentially a lack of lubrication. Bad for the engine, but not as bad as other things might be. Hopefully the problem is limited to the head.
I thought it was a crack too, but actually it's just mucky casting. The head seems fine, but I'll have to give it a more thorough check over tomorrow.
Since I'm unsure exactly what the problem is, I'm in the process of examining the timing cover to see if there's a hole in it.
Is RTV used in place of a head gasket, or is it applied in addition to one? Would using just RTV in place of a gasket leak easily?
Since I'm unsure exactly what the problem is, I'm in the process of examining the timing cover to see if there's a hole in it.
Is RTV used in place of a head gasket, or is it applied in addition to one? Would using just RTV in place of a gasket leak easily?
RTV is not a good substitute for a head gasket, but it could be used as a quick fix for gaps and holes, though I have no idea how long a fix like that would last. RTV is not designed to take those kinds of temps and pressures.It is more for sealing seams from fluid leakage. You'll find it pretty common where there's a coolant or oil joint without moving parts. Rocker covers, water pumps, timing covers, etc. It comes in different grades, for varying applications and in varying viscosities.
the "crack" is a seam joint in the casting. nothing wrong with it it is normal. the red rtv is nissan rtv that is only sold through nissan parts departments. this silicone is not used by the factory during initial vehicle assembly. where it is being sealed is fairly common during a front cover reseal on that engine. it is done since the cover is removed from under the head without removing the head. it is only applied where the 3 joints meet (timing cover, head, and block) and may be applied across the front between what is left of the head gasket and the timing cover depends on how much of the head gasket came off during the cover removal. the area where it is sealing experiances very little pressure since it is crank case area. you could have one of 2 problems here coolant passage under head to block leaking to an oil passage. or a front cover water pump jacket leaking into timing cover area. recommend taking valve cover off. puting coolant in and pressurize cooling system with a pressure tester. look into the timing cover and see if you can see coolant spraying in. you'll need a flash light to see well down in there.