What are some symptoms of a cracked engine block? It is a '94 Nissan xe kingcab, 4cyl ka24e engine. 2wd. It was running warm one evening, so after it cooled down I checked the water level and added a little water. After that it ran fine (we drove it around for about 40 minutes to get up to temp). On the way home from work the next day it started to overheat about a quarter way on a 20 mile commute, I added approximately a quart of water to the radiator after it cooled down, but then it wouldn’t start. I checked the oil, and the level was a 1/2 inch or so over the full mark, and there was water in it. I have pulled the cylinder head off, but do not know what to look for to determine if it is a blown gasket, cracked or warped head or cracked block. I did not see any oil floating on the water in the radiator filler cap. About 2 weeks prior to this, it was in the shop and had to have the air intake sensor replaced. The mechanic said that after putting it back together, he had to drain and replace the oil because there was gasoline in it. Apparently it had gotten there from all the cranking over I had put it through trying to diagnose the problem. He added some slik 50 or something similar to it when he added the oil.
Please help me keep from having to replace the engine/vehicle.
A cylinder head and/or gasket I can handle. I don’t have the $$$ for anything more.
First off, I would run away screaming from any ‘mechanic’ who uses Slick 50. It is complete crap.
Overheating a 4 cylinder, aluminum head engine is very, very likely to have blown the head gasket. And I can’t think of any way overheating would crack the block, so I’d say its the head gasket. You can (and should) take the head to a machine shop. They can tell you if its warped and machine it flat.
I’m pretty sure it’s the head gasket. I’ve seen those blow with little or no indication that they had been damaged.
Usually, if the cylinder head is cracked, you’d have noticed it. The cylinder head should be checked for being warped with a very good straightedge - a local machine shop will have no trouble testing it and it shouldn’t cost that much.
A diagnostic tip: Take off the OIL cap and look at the inside of it. If it has anything resembling fluorescent green antifreeze on it, your engine is fckd. If it does, get yourself to a used car lot ASAP and trade it in.
Sounds like a blown head gasket to me. Have the head surfaced, install a new head gasket and while your at it, change the timing belt too. If the head is cracked it will show up while being surfaced.
It wasn’t actually slik 50, it was that stuff that they display on the parts counter in the rear of Discount Auto Parts… the stuff in the plastic case with the gears you turn to show how it keeps the gears coated.
Anyway, the guy is a friend of the family and he’s always done good work for us so I know that he’s not a hack.
Thanks for all the great responses, I’ll have it surfaced and see what they say. I’ll keep you posted
The presence H20/coolant in the oil is not necessarily indicative of a cracked block, it probably got there by leaking past the blown head gasket into the cylinder(s).
You should be able to look at the top of the block, with the head off, and see where the gasket has failed.
A couple tips…
Your head probably uses ‘stretch’ bolts, which actually stretch as you torque down on them. If this is the case, you cannot re-use your old bolts. When you get the new gasket, get new cylinder head bolts and use them, or you’ll be replacing the head gasket again real soon.
You must torque the cylinder head bolts to manufacturer’s specification, following the prescribed sequence (including loosing and re-tightening), or you’ll be replacing the head gasket again.
The head itself can be machined and pressure tested to ensure its integrity. Take it to a decent auto machine shop and have them do it.
When removing the old gasket, use a gasket scraper (taking care not to scratch the mating surface), and finish the job with acetone. Also, avoid at all costs getting gunk in the cylinders. Stuff them with clean lint-free cloth if you must.
Use a moly-based grease on the ends of the pushrods and the rocker-arm fulcrum to avoid damage before the oil pressure builds.
Check your water pump, thermostat, and have your radiator cap pressure-tested while you are at it.
Cracked blocks are rare, talked about much more than experienced. I’ve seen 2 in a 30-year career in auto repair. In both cases, the cracking was visible. Drain the coolant completely from the block to see more of the coolant passages, check inside each cylinder with its piston all the way down. If you see a crack, you know you have one. If you don’t see one, it’s very unlikely, though I wouldn’t say impossible. If you want to be certain, talk to a good machine shop about testing it (I’m not sure it’s feasible without completely disassembling the block, but the machinist should know.)
Cracked heads are seen more often. In some engines they’re common enough to be expected, in others they’re rare. I don’t know how common they are on that engine, but it’s always a possibility. Not all cracks are obvious to the naked eye. The wise thing to do is have the head pressure-checked at a good machine shop. Otherwise, you’re taking a significant gamble if you re-use the head. (I’m not a machinist, but I wouldn’t count on cracks always showing up during resurfacing–ask the machinist to be sure). If it does not show cracking, have it checked for flatness and resurfaced. I assume it’s an aluminum head, which makes it a virtual certainty that it’s warped.
If WATER has gotten into the oil, that’s not really a concern. If ANTIFREEZE has gotten into the oil, that’s a HUGE concern. Antifreeze destroys crankshaft bearings in short order. How much antifreeze and how long it’s been in there are significant factors. I’d investigate this aspect before spending any money on the head.
Head gaskets do not need to be scraped off. I have removed oh, 3 or 4 hundred and not once did I need a gasket scraper. The old gasket should easily lift off. There may be some residue left, lightly clean with scotchbrite and carb cleaner. You risk scratching the mating surface, this would ruin the block and of course, the engine.
You should be able to reuse the head bolts on your Nissan. If the unthreaded portion of the bolts is smooth, clean them up and reuse them. Interference fit (or stretch bolts) have a wavey look in the unthreaded part. These kind must be replaced. But Chilton’s manual says Nissan did not use these kind of head bolts. The only thing you have to do prior to torquing the head is but a light layer of oil or anti-seize between the bold head and the cylinder head mating surface. And always tighten the bolts by the manufacturers suggested order.
Do not loosen and retighten the head bolts!!!. Modern head gaskets will fail if you do this. That is something that was done with the old solid copper head gaskets (not used since the 50’s). If for any reason any one head bolt must be loosened, take them all back out and install a new gasket.
Uhhh, Nissan engines have not had pushrods since the days of the early Z cars. All modern Nissan engines are overhead cams and do not have push rods.
