Diagnosing head gasket

[playairguitar]

Hi. I was hoping someone with experience in head gasket diagnosis can help me out. I have a basic know-how of automotive mechanics but my knowledge is limited by experience. I'll start from the beginning.

A friend of mine recently bought a 1989 240sx with the KA24E engine. It drove fine for about two months, when he overheated. What happened was the alternator adjuster broke (the same belt drives the water pump). I repaired this and the car drove fine for another few weeks. He called me and said that there was a ticking sound coming from his engine. I came over and surely enough, his valves were ticking. I checked the oil and the oil was a brown milkshake color. From this I knew that engine oil and coolant were mixing together with the crankshaft acting a whipper/mixer. From my knowledge, the only three things that can cause this is (1) blown head gasket (2) cracked head (3) cracked block. In order to try and verify that it was the head gasket, I ran a compression test on the engine. All four cylinders came out within spec (however, the 1st puff test was low due to the mileage on the engine).

I couldn't rule out the head gasket because if it blew between the coolant. passage and the oil passage, it wouldn't show up on the compression test. So we pulled the head off the engine to see the condition of the head gasket.To me the head gasket looks fine, indicating a cracked head or a cracked block. However, I am seeking a second opinion and if anyone here has any experience in these matters, please comment. I am posting the pics of the head gasket below. If you know what I should look for or any other way to further diagnose this issue, please let me know.

Thank you,Joe

Head gasket:

[TheOne]

compression test wouldn't have exactly shown a bad headgasket, a leakdown test would have though.

more than likely the head is not cracked, but it could have been warped due to overheating(the headgasket itself is quite durable, the head on the other hand, isn't because its aluminum), warping could make coolant leak down, and would not show on the headgasket itself, get it checked for warpage and resurface if needed(more than likely), if its too out of spec, get another head.

[ricebike]

KA24E or the SOHC engines are notorious for the timing chain-eating-thru-da-guides-&-part of the timing cover water jacket(s)

as seen on this thread:

click on me for more info;one of many threads w/ this engine

When the engine becomes excessive in high mileage over 100,000miles, the timing chain as well as the guides become weak and old. Once the chain is given too much slack. The chain then begins to grind into the front cover where the location of the coolant pump assembly is found. At any given point once the front cover has been grinded into too much, coolant from the coolant passage begins to leak into the oil pan. This is a problem that should be corrected IMMEDIATELY as it will cause hydrostatic locking withing the cylinder and can bend a rod and destroy the valve train....

there was also a recall on the early 90's about this problem of the 89-90 SOHC engine w/ plastic timing chaing guides; the newer sets will now have metal-backed plastic coated timing chain guides as their replacements

[playairguitar]

I did notice that the timing chain guide was chewed up - actually it was loose and being knocked around.

should the water pump be replaced as well?is there anything else I should replace if I plan to replace the head gasket, timing chain and guides?

thanks for your help,joe

[pmion13]

timing chain went into timing cover same thing just happened to me