So i recently swapped from X-Fire to TBI and was taking it for a test drive. I started her up and everything was normal. Cold idle with 67ish PSI. Then i started driving. Now at some point during this drive, the oil heated up to 300* F at which point a red light came on and flashed the temp at me (I had it on Oil Pressure). I immediately pulled off into a parking lot. I realized that I had blown the lower radiator hose loose and was leaking coolant. I also realized that my TPS was malfunctioning causing my engine to run very lean which caused my oil to heat up so hot in combination with the coolant leak. Right before the oil had gotten so hot though, i had noticed my idle PSI was at 10, and my load PSI was 20. I later attributed this to the hot oil, until I had fixed the coolant leak and started it up again and my oil pressure was now anywhere from 5 to 22 PSI. This morning I went out and cold started it and got a PSI of 45 (obviously because the oil is more viscous). I was wondering if I could have stuck the relief valve open by dropping some dirt or anything into the engine while I was changing the intake. What do you guys think?

 

What does the oil look like? Real dark, real thin, milky? Any loud noises coming from the engine? If the oil temp was 300, the coolent temp was probably higher. It doesn't sound good.

 

I looked at it yesterday and it was dark brown, maybe a little thin. But it looked like it normally does. Coolant temperature never registered over 200* on my gauges. Even when it's full on coolant, i could sit there and watch the oil temp slowly raise up to 270*. Assuming the engine is running lean, could the excessive cylinder heat cause this? And if the engine weren't running lean, could the low pressure cause this?

I should also note that when I say "blow off" it didn't literally blow off and drain out all the coolant. it just loosened it up under high pressure and i had a small steady stream of coolant flowing out. Maybe 1 Gallon per 15 minutes.

 

Is it making any knocking noise? I suppect you spun rod or main bearing and that is why the oil hit 300 degrees.

 

Nope. No knocking. My dad was a mechanic for 15 years, and he thinks it doesn't have a spun rod bearing.

 

Id pull the oil filter. Cut the housing off with a pair of tin snips. Good Luck

 

I would at the minimum do an oil change and replace the filter and keep an eye on things - temps up that high probably caused some of the viscosity stabilizers to break down... Then get the lean condition fixed before taking it out for another run.

 

Pull the filter and cut it apart and look for metal flakes, I do not believe a lean condition will cause enough heat at light throttle to get the oil to 300 degrees. I could be wrong, but I have doubts.

 

Certainly change the oil and filter, look for signs of a trashed bearing. I also would lay hand on a known accurate oil temp sender. Oil temp at 270 and coolant temp in the 200 range isn't right.

 

No metal in the filter that I can tell. Oil is black and milky.

 

Milky not good

 

Well maybe milky is a bad description. It was really black and looking at it, I can see small lines of lighter discolorations. I've never seen oil this black but then again, I'm pretty sure The car sat for a while and built up some sludge. Could also be a small amount of antifreeze from changing the intake.

 

 

When a modern Multi viscosity engine such as 10w30 oil gets real hot like to 300 degrees F or higher, the oil gets as thin as water.

Most oils start to or will break down at those temps very quickly.

Only a few premium dino oils or synthetics will take that kind of heat without breaking down.

Oil pressure will drop alot at those very high oil temps too.


Change the oil and filter, run the engine and closely check it over before driving again.

BR

 

The coolant will not go much over 200 with no water in the engine as that is the temperature of the steam in the cooling passages. If you have oil temps that go to 270 you either have a bad oil temp sensor or a very hurt engine. It does not need to make bad sounds to be broken. I would change oil and filter and check oil pressure with a mechanical gauge. If the pressures are what you say they are with a mechanical guage stop driving and pull the pan and check the bearings before you really hurt it.
Dave

 

Okay. I changed the oil, and while cold, the pressure was around 55 PSI. When it heated up to 200*, it was 9 PSI @ idle, 19-25 PSI @ Cruising, and 29-35 PSI @ Step on it. I noticed I had a MAP error on the ECM and realized the problem was a vacuum routing, so I corrected it and it began running tons better. So I'm putting my bets on the MAP sensor was causing the engine to lean out and run hot, plus the loss of coolant, overheated my oil. I'm also thinking, the dirty oil may have deposited something into the oil sender, and that's why i'm reading low pressure. I'm waiting on a mechanical gauge now so I can check it. As to the oil temp, it was at 200* after a 6 mile run. As for the engine itself, it wasn't running so great... still seemed to be starving for fuel.. i'll have to check the TPS.

Here's a video of it running and you can see the oil pressure and temp.
http://www.youtube.com/watch?v=nYPJdDLs_IE

 

Hookup a mechanical oil pressure gauge as Dave suggested.

A good oil pressure gauge that you can trust. Like AUTOMETER.

Not a cheap China unit like at Autozone or elsewhere.

A Snap On hand held oil pressure gauge can be trusted 100 % also.

9psi is just low oil pressure at idle when hot.

If you get the same readings with a good mechanical oil pressure gauge, remove the oil pan.

Check every Main and connecting rod bearing. Not just 1 or 2 as many guys do.

Brian

 

Well the problem finally showed up. I've got a main bearing out. It started knocking today.

 

Don't start the engine today. Or any more till you get the oil pan off.

Unless you want to blow the engine up sky high in your C4.

Get the oil pan off.

Remove all 8 spark plugs. This makes it much easier to roll the engine over by hand with a breaker bar or ratchet.

Also remove the serpentine belt too. Also makes it much easier to check all the main and rod bearings.

If You are lucky, you can roll new main and rod bearings in.

I have "ROLLED Main and rod bearings" into engines into with motor installed in the car a thousand times.

Large Diesel Trucks like Mack, Kenworth, Peterbuilt, Caterpillar, Deroit Diesel I also have replaced bearings in too.

Very common practice yet to Roll Bearings in diesel engines. You dont want have to pull the engine out of large trucks unless you have to, much heavier engines.

I am also a Diesel mechanic besides a Former GM Master Mechanic.

Crankshaft journals must be in good shape 1st.

Must also know the size or undersize of the bearings installed right now.

Micrometer check the Rod journals if necessary.

There is a special tool for MIKE-ING the Main Journals with crankshaft installed in the engine block.

That tool is hard to come by now. A Vintage tool. Made by Federal Mogel in the past. I have them.

But plastic Gauge will work too. More readily available.

A small block Chevy on the street........Like to see .0015-.002" Main and rod oil clearance.

Thats running 10w30 oil.

Takes skill and dexterity to roll main and rod bearings in by hand with the engine in the car yet. But can be done with precision and accuracy if you work slowly and work carefully.

Brian

 

Bummer Josh sorry to hear about the bearings. In frame bottom end is not fun but the cheapest route I see. Journal condition is critical. Checking clearance is a B!%$H. Keep in mind that the crank is not laying in the bearings, there are seals clutch ect. Can you afford a rebuild? Do you have the time and the room? Let us know what your recourses are we well be happy to help.

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