pricebill Posted January 2, 2015 Share Posted January 2, 2015 (edited) Happy New Year everyone. I'm a complete newbie at diagnosing engine failure and thought I'd see if forum members might be able to help. Our 280Z has been racing in the 24 Hours of Lemons and appears to eat bad made-in-China water pumps. During our last race we replaced failed pumps twice and then found water in the oil. Thinking the head gasket was blown we pulled the head a few weeks after the race and found excessive water/rust in cylinder 1. The engine started and amazingly ran before we pulled the head. The head gasket itself appears to be in good shape; do we have a cracked block? Pictures attached and opinions desired. Thanks in advance. Cylinder #1 as it looked when we pulled the head. Here's the head showing rust just on cylinder #1. Here's cylinder #1 cleaned up and rotated down to check for cracks. Edited January 2, 2015 by pricebill Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 2, 2015 Share Posted January 2, 2015 More likely a cracked head. Or a porting job has busted in to a water passage. These issues and pressure-testing to find them are described in the How to Modify..., and How to Rebuild, books. A picture of the head gasket would probably show more about whether or not it is the problem. The rusty water indicates that you ran without the corrosion inhibitors that come with coolant. That's not good. Quote Link to comment Share on other sites More sharing options...
pricebill Posted January 2, 2015 Author Share Posted January 2, 2015 Agreed on the rusty water and lack of corrosion inhibitors. Lemons race rules allow only water on the track, no coolant. Here's a full pic of the head gasket. Close examination of it doesn't reveal any tears or missing pieces. Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 2, 2015 Share Posted January 2, 2015 Can you add corrosion inhibitor? You can buy it separate from the glycols. Anyway, I'm way out here on the internet and I think I see signs. I'd pop the gasket off carefully and examine it closely, with a magnifying glass too, to be sure. Don't forget that a single overheat can warp the aluminum heads. You've had several with what might have been a bad water pump. Check the head for straightness. You might have had an initial overheat from a pump, then leakage due to head warpage. It's a downward spiral. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted January 2, 2015 Share Posted January 2, 2015 Cylinder number 6 no? Do you have compression numbers prior to when you pulled it? Understandable, most tracks don't allow the use of coolant, but maybe you should flush the water out between race dates and add some evaporust or coolant. That seems to be quite the accumulation. A crack is going to be pretty hard to find if it is hairline. You can try filling the block and see if any water spills into the cylinders overnight. Have you taken a straight edge to see if the mating surfaces have warped? I agree with new zed, a picture of the head gasket by itself might help. Ideally the head gasket should blow before the engine cracks. Quote Link to comment Share on other sites More sharing options...
pricebill Posted January 3, 2015 Author Share Posted January 3, 2015 @seattlejester yes, I suppose it is cylinder number 6 that is featured here. Good advice on the flushing of engine after racing. Quite frankly we're complete mechanical amateurs and surprised in our attempt to get this engine back in shape for a THIRD attempt at a Lemons finish. Gluttons for punishment. Sorry to say that I don't have compression numbers before head removal. Amateur mechanics at work. The day before we pulled ithe head I purchased a leakdown kit from Harbor Freight and didn't even bother when I saw how much water was mixed with oil in our poor engine. A trusty Sears compression kit was also standing by but in our naivety we just didn't even bother. Next time. LA Machine Shop is two blocks from my house and I'll take the head there on Monday morning for a professional eval. We'll see if NewZed correctly diagnosed a warped head/blown gasket on the other side of the internet. Thanks to both of you for offering sage advice to a bunch of idiots. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted January 3, 2015 Share Posted January 3, 2015 No worries, quite a bit of an amateur myself. The books NewZed mentions are very good books to read/browse. Not a bad call on being hesitant on the compression test due to fluid. Although next time, if you are in a similar situation, drain the coolant, pop out the spark plugs and crank it over without fuel or spark to force the fluid out of the cylinders, then put the spark plugs back in and run a compression test, it would really help isolate where to look for a problem, granted we have a pretty strong grasp on the problem cylinder, it might have shown some other weak cylinders. As you said, next time. From the picture of the head it looks like cylinder 4 was not happy either. The circumference around cylinder 6 also seems to be real unhappy, although there isn't a visible mark at least from the pictures that leads me to think the leak is from the head gasket, granted that style of head gasket can crack if you bend it out of plane a bit. Hopefully the shop has some news, I want to lean towards punctured water jacket via intake/exhaust stud personally given the quantity of fluid, followed by cracked head gasket, then cracked block. Quote Link to comment Share on other sites More sharing options...
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