Low oil pressure after rebuild,what could be wrong?

[sil80drifter]

Hi,I've rebuilt my 240SX KA24E recently. I honed the block myself to the new pistons, and fitted the rings and all new bearings to spec and within (stock) limits. The only gasket I did not replace is that little one on the block oil feed hole on top (on the pic, it's between cylidners 2 and 3, on top). But I doubt it could cause the problems I'm having (descrived below). My oil pump is brand new from a 280Z and has worked before the disassembly for abotu 2 weeks. I assembled everything with engien asembly lube on all rotating surfaces, like main and rod bearings and camshaft and rocker arms.

I knew my valve train was a littler loud before the disassembly, but it was just one or two rocker arms that kind of tapped because I th ink they were clogged. When reasembling the head I cleaned the heck out of the cam and rocker arm shatfs and all the rocker arms and made sure no air entered them.

So here is the deal: I tried to start it yesterday and it did (timing was a little off, had to take off the pump and re-align the distributor), but it runs kind of rough, smokes a decent amount of oil from the exhaust, and worst of all the oil pressure is REALLY low. Idle pressure is about 4-5 psi, and at 3000 rpm it doesn't go over 30psi. I know that it should be at least 11psi at idle and around 60psi at 3000 rpm (even in neutral it shoudl be at least 45psi at 3000rpm). I am clueless as to what the caue is. I doubt my bearing clearances are SO big as to cause a drop in pressure THIS big, and I don't know what else can cause this. I am thinking of shimming the oil pump pressure regulator to see if that helps but... that just seems liek a desperate move. The head/rocker arms are really loud because of the low presure.

Also take a look at the pics of the oil I just drained after yesterdays 20-30 minute idle and half a block of driving (then the engine started overheating and I turned it off and rolled it back home). It's not dirty the way oil usually is, it's clean but with particles in it. I'm really worried.

What do you think?

sil80

Oil hole in block, that's the one gasket I didn't replaceDirty Oil 1Dirty Oil 2

p.s.: the numbes on the block/pistons were for my own reference, please don't think I assembled the wrong pistons into the wrong cylnders.

[sil80drifter]

Well, I shimmed the pressure regulator on the oil pump and the oil pressure is back up (weird, the pump is new, I don't get it really).

The car still overheats like crazy though, one side of the radiator is cold and the other steaming hot. Those are usually signs of a bad thermostat, but mine is brand new Nippon Denso. Going by the same "ghetto it" fixing technique, I may just have to gut the thermostat and see if that helps. Anyone have any suggestions?

sil80

[InsanityInc]

Well, I shimmed the pressure regulator on the oil pump and the oil pressure is back up (weird, the pump is new, I don't get it really).

The car still overheats like crazy though, one side of the radiator is cold and the other steaming hot. Those are usually signs of a bad thermostat, but mine is brand new Nippon Denso. Going by the same "ghetto it" fixing technique, I may just have to gut the thermostat and see if that helps. Anyone have any suggestions?

sil80

Replace it, don't gut it. My bet is you may have installed it wrong, or just got a bad one.

[180fan]

Yes, check to make sure the opening is pointing up on the thermo.

Did you make sure everything was where it should be for the oil pressure to be up before you shimmed your pump? I had forgotten the front timing chain oil jet before and that caused low pressure, check for stuff like that.

[sil80drifter]

I don't think the SOHC has a front timing chain oil jet, there are no parts to attach to the front of the block except the tensioner and the two guides.

As for the thermo, this is not my first time replacing one, and the FSM is pretty clear on how to do it, (opening up etc) so I think I got it in right.

I am wondering if there is such a thing as directional flow in a radiator, because I have an aftermarket one, and it was not made for the KA but for a Ford. It has a top right opening and a bottom left opening, and maybe I hooked the wrong hose into the wrong opening? I'm not sure if that makes sense, because I am not very sure about direction of flow mattering in a radiator but... who knows?

sil80

[Chezedik]

You have air in the coolant. I am assuming you did not boil-check your thermostat, but that is the general problem people have.

[Chezedik]

If this is the case you will find that the coolant temp gets high for a while and then shoots down. Given your modified case, I would suggest finding the highest point on the motor, drilling a hole and tapping it. Then run a bolt in. You will be able to add coolant, and then when the coolant comes out of the hole, you will know air is removed from the system.

[180fan]

The SOHC does indeed have a oil jet. I remember trying to pull it off so I could use it in my SR but the bugger wouldn't budge.

With the thermo, in the FSM it doesn't say explicitly to have the jiggle valve up. It doesn't have to be pointing up, but it'll be murder to bleed the system.

Radiators last time I checked didn't have direction. I just remember that the upper hose went to the intake manifold and the lower hose went to the thermo housing. Keep at trying to pack in coolant in there too.

[Chezedik]

Are the jets interchangable like that? The DE uses a bleed system like I discribed, does the E not? And no, most (Cross flow) radiators do not have a flow pattern, but if it is down flow like an older ford may be, it might. Just check to see what way the radiator core tubes run up and down, or side to side.

[180fan]

Yes, they are swappable. If you check em, they've got the punch mark in the same spot, and have the holes for the oil jets in the same spots.

There is the air bleeder hole on the intake manifold assembly as well.

[sil80drifter]

I gutted the thermo, refilled the coolant (which probably got rid of my air pocket problem) and the car was doing just fine. The radiator is side to side btw, so it's not directional ( I researched it yesterday). Interesting fact about the oil jet, where exactly is it at?

Here is my problem now:I was driving (test driving) the car up and down the street, and it was fine for about 7 miles, then I filled the gas tank up (full), it drove 2 more miles and just died. No noises, nothing out of the ordinary no "blow up" or anything. It was driving along, then the gas pedal stopped responding (I press it, but revs don't go up), then the lights went dim and it died. I "clutch started" it as it was still rolling, it started and died again, and again after I did it again. Gas pedal does absolutely nothing it seems. And it will crank but not start. I checked all fuses (all intact), checked for vacum leaks (non that I could see, the hoses are on pretty tight), checked if there is pressure in the fuel lines (there is), and checked my battery connections. The car gets power, the lights will go on, the fuel pump will prime, and everythign else seems to be in normal condition. WTF! The only thing I didn't check is spark but I will today. I have no idea what could be the cause for such a sudden loss of response of the gas pedal. I checked the MAFS and Throttle Position connectors, they are on tight. Anyone have any ideas? It's like if it's not one thing it's another.

My car has vey stiff engine mounts so it vibrates pretty harsh, which is why I double checked all my connectors, but they all seem to be on fine.

Any ideas, guys?

sil80

[Touchdown038]

Bad gas maybe?

[deviousKA]

Hey Sil80drifter,

Where is your aftermarket oil pressure gauge tapping in? I assume you have a tee off original location, or just removed oem, or?

So you shimmed your oil pump spring a bit and pressure is back up within range? How much did you shim it? Not all 280 pumps are the same, but im sure you ordered the turbo version.

Dont worry about the oil sprayer post/jet for the timing chain. This is not causing an excess bleed of oil. Even damage (chain drag) will do nothing except make this sprayer smaller or even plug it.

Have your lifters cleared up after you upped the pressure? It is all to common for these to rattle for extended periods of time even with minute damage. What are you setting your oil level at? Set it to mid range, and dont overfill.

What was your base timing before it started to overheat the first couple times, and what was it when your car died? Was it running fairly decent up till then, or was it still smoking and running rough a bit?

Id check that spark first, then ecu (codes), and then get a noid light or similar tool to monitor the injector firing. If your unsure if the injectors are firing, you can just keep turning it over untill you can smell rich/gas or spray a couple shots of starting fluid into your intake to see if it pops.

If it was performing correctly (all things considered, new engine) before it died, id be looking electrical/efi. If it was sputtering and still smoking a bit for those 7 miles you have more to look over.

BTW, nice pistons , from the looks of your cylinders you didnt get to heavy with the honing, be sure to take extra care when breaking those rings in.

[sil80drifter]

Devious, I was doing everything you mentioned, checked the ECU, smelled the fuel, and finally did a compression test, just for the heck of it.This was when I figured out the problem.Cylinders 2 and 3 had 0 compression, while 1 and 4 had about 30.This was way too weird, because I know piston rings don't just go without a fight (especially all four), so I thought I'd open the valve cover to see if some valves were stuck open.

I took off the valve cover, firstly noticing that there was suspiciously too little oil on top of the head.

Secondly, I noticed that the cam sprocked was lying inside that littlle gap, all by itself, with a ripped piece of timing chain on top of it. The cam bolt must have come loose during operation (stiff engine mounts, and I may have forgotten to tighten it extra hard and use locktite) and it all went to hell from there. I wonder how many valves got bent. I didn't hear any cracking or other odd sounds, so maybe they didn't. But the KA is an interference engine, and I've tried to start it about 20 times after it "died." *sigh*

Well, I wish there was a way to check for bent valves without taking the head off. But I guess there isn't. So I'll take it off, and see how much damage there is. The timing chain guides are totally busted and look ripped, laying on the sides of the timing cover. At least they were new timing guides, with metal insiide so they didn't let the chain rip into it.

*sigh*.

poopies.

I'll take sympathetic or "you retard how could you not have tightened the damn cam bolt" remarks now.

The thing is that I've put the head on and the engine in in June, then left for vacation, came back two weeks ago and forgot about double checking it for tightness.

*sigh*

I hope someone (besides me) learns from this. ALWAYS TIGHTEN ALL BOLTS AND DOUBLE CHECK THEM TOO.

sil80
Modified by sil80drifter at 10:55 AM 8/29/2005

[180fan]

Oh damn, sucks to hear. Hopefully the damage won't be as bad as you fear it is.

[sil80drifter]

Well, here are some pics of the disaster:Me holding the ripped chainCam bolt and the gang chillin in the head.

I took off the turbo manifold and the valves didn't look out of the ordinary or anything, I wonder whether I can tell by looking at them like that, and from the intake ports, if the valves are ok or not. I really don't wanna take the head off, but I will if I have to.

Has anyone tried checking the valves by just looking at them from the intake/exhaust ports?I'll take pics tomorrow and post them.

Oh I JUST figured it out (well looked up online, really)! To see if the valves are bent, I'll loosen the rocker arm shafts (so all the valves would close) and test compression again. If a cylinder leaks, then the valves are bent, if not then not. Updates tomorrow!

sil80

08/30/2005: This thread is continuted here:zerothread?id=133450
Modified by sil80drifter at 10:49 PM 8/30/2005

[Chezedik]

that sucks, I am sorry.