crazyd

My car (350 GM crate ZZ430 w/ '92 TPI) has been down for about four years during a long-term project to upgrade to headers. Once I got it back up and running in February, I noticed my oil temp gage was running high. It would start out normal for the first few minutes, but then would start climbing rapidly all the way to the peg at what I guess is about 320 degrees F by about 10-15 minutes from start. I couldn't rationalize this because coolant temp is running perfectly normal at 190 or so. I figured maybe it's the headers since the sensor is right underneath them, and I need to think about making a heat shield for it or something. But I also looked back at my maintenance logs and discovered I hadn't changed the oil on this car since '07, but haven't put even 1,000 miles on it since then either. Nevertheless, new filter and new synthetic 10W-30. Been driving it to work every day and checking the oil on the stick. Crankcase isn't smoking, smells normal, all seems fine. 20-minute drive to work every day, mainly been driving this car. Not sure what to think, but the drive is short enough that I don't think I need to worry.

Then today I noticed, about 1,000 miles from the last oil change about 2 months ago, that my oil pressure had dropped to the very top of the red zone, about 1/4 of the gage, what I assume is about 20psi. It usually runs around 40-50psi. Thinking that it might be the oil thinning out too much from the temps, I changed it tonight to Mobil 1 10W-30. It's still just barely above the red, maybe 25psi cold.

Total miles on the motor 23k. Running perfectly otherwise. I'm suspecting rod bearings. Any other diagnostics I should try or things to check before tearing down the bottom end, or is it not quite time to freak out yet?

DARKmj16

iTrader: (6)

wrong bearings. if it was rods you would hear them knocking. I would suggest checking the oil pressure switch, bc well its a hell of a lot cheaper then cam bearing. most of the time low oil pressure is a spun (or more) cam bearing... and if its only 23k miles I would be calling for warrenty swap, assume the time limit hasn't passed (or mile limit)

fun fact, if you switch the oil to say 20w-50 or just a 20w or 30w you wont have low oil pressure anymore. but you'll still have a spun cam bearing.

crazyd

Oh. That's... an ugly possibility. It could probably also explain the high oil temperature, maybe a cam bearing was somehow overworked and finally let go. Can't imagine there'd still be a GMPP warranty after 12 years and 23k miles.

Damon

Double check your oil pressure. The factory gague (and ESPECIALLY the sender) are notorious for going flaky on these cars. OP sender is screwed into the block just above the oil filter boss (3-wire plug). If in doubt, replace it. When they go bad, 9 times out of 10, the oil pressure shows lower... and lower... and lower until you're running around with the thing barely ever coming much off of zero.

crazyd

Thanks Damon, it's definitely worth checking. I'll call the local parts store and see if they have a loaner I can check it with. I really doubt I have had something major fail, though that definitely wouldn't be my usual luck with these things.

DARKmj16

iTrader: (6)

if the engine was sitting for 12 years... or more then I say one year, where do you think all the oil that normally stays on the cam bearings would go? chances are IF there is a spun cam bearing it would of happened when you started it up after sitting for so long (lack of oil there at 1st)

hope its the sender though, cheap and easy.

crazyd

Good point, and yeah even though it has been sitting for the last 4 years, I have still started it up and run it every so often to keep things lubed.

I was going to replace the OP sender but the parts guy at Autozone couldn't figure out what it was. It has the standard-for-the-era GM 3-prong oval connector and black barrel a-la '92 F-body, but it has a small snout with a 7/8" SAE thread that goes to an adapter mounted next to the distributor, apparently at the distributor drive. You can see it in this pic.

http://zz430fiero.com/mvc-174f.jpg

I'll have to call S&P on Monday to find out what the hell they used.

crazyd

Good news, I found metal chunks in the oilpan when I drained it.








It's UPGRADE TIME!

Damon

Awesome! Congratulations on the metal chunks! You must be..... thrilled. Or perhaps not.

I was just stopping by to post about that OP sender.... it's the original type, just screwed in up top with adapters because it's normal attachment point is obviously occupied by something else just above the oil filter boss. What is that?? (I'd hate to find out that's for an oil cooler, because I can't imagine where they ran the return.)

I'm guessing this install is a bit jacked up because it's going in a Fiero (transverse)?

Hats off to you if it is. I love hot-rod Fieros. My brother did one with a 3.4L TDC Lumina Z34 enigine for autocross and road racing. Now he's got another 3.4L TDC in an 88 with a turbo that's been in the works for a few years.

crazyd

Yes, the configuration would look a bit jacked due to being transverse for a Fiero. What I think you're seeing is the oil filter relocation adapter, because that's where the starter has to go in a Fiero. And I have 2 of these '88 GTs, the other one has that same 3.4 TDC in it.

This happens at a somewhat disappointing time because I just got the bastard running right with the new headers after 4 years, but I am psyched because I just found a local builder who specializes in short-stroke SBCs who has an extra .060-over 400 shortblock he wants to unload. So this just became my new 6.8-liter ZZ430 project. And it's hard not to be a little excited about the prospect of a 413 cube SBC that turns nine thousand RPM in a badass little Fiero, even if it was borne of a chunk-spewing bearing failure.

crazyd

Wanted to update on this. The first thing was that once I removed the chunks I found in the oil and let the oil drain off of them for a day, they didn't look like bearing material at all. It was metal, but it was so fragile it crumbled in my fingers. Must have been random stuff that fell in the pan while I checked out other things, because none of it was shiny and there weren't any flakes in the oil.

Next, I have continued to drive the car and I noticed some strange behavior from the oil pressure gage. At startup it was showing 60psi at one point, then about 30 seconds later as I watched it suddenly, instantly jumped down to 20psi - making me almost certain this points to a gage or sender problem and not a real engine failure.

Then it turns out I have not one but two oil pressure senders. One runs the fuel pump through the ECM, the other runs the gage. The one I showed in the pic above near the distributor runs the fuel pump, not the gage. So I'm checking the wiring and replacing the other sender later today.