reuse oil cooler after a rod bearing failure?

alniki · 06:00 PM

Have read in Wayne's book and Excellence about replacing the oil cooler and probably oil pump after a rod bearing failure as 'the metal shavings can go everywhere'! But isn't all oil in the crankcase go to the oil filter first before recirculation to the oil cooler and pump? Unless with a bad oil filter or bypass there should be no metal contamination in the oil going to the oil cooler/pump. Have I missed anything?

dad911 · 06-21-2009, 05:57 PM

No, filter is on the tank, except for 3.6 993. Oil from engine goes through scavenge side of pump, then lines, thermostat, cooler, then filter/tank.

alniki · 06-21-2009, 06:03 PM

But according to the oil circulation diagram of the Bentley manual for Carrera 3.2, the scavenged oil goes to the oil filter.

Mo_Gearhead · 06-21-2009, 06:04 PM

You have to consider that the 'scavenge' side of the oil pump is in danger of damage when a main or rod bearing fails ... metal can/will fall into the 'sump area' and immediately be picked up.

Street car?
Track car?

(You apparently have the engine apart (to conclude the bearing failed)

Some will say trash/replace the cooler, others might opine to sonic-clean it and re-use.

You may get several opinions on this.

dad911 · 06-21-2009, 06:26 PM

Scavenge, 'stat, external cooler, then back to tank.

Oil filter (except 993) is just before tank.

alniki · 06-21-2009, 06:35 PM

Thanks! It's a weekend street car but always run at high rpm, even on lower gears when high speed is not allowed. Engine alread disassembled to a short block, case was broken, crankshaft stuck, big end of one rod disrupted and crashed.
I also think the scavenge side of the oil pump have a higher probability of damage than the oil cooler. Is there any way to test the oil cooler for damage/malfunction?

dad911 · 06-21-2009, 06:42 PM

Problem isn't necessarily damage, it is getting all of the oiling sytem perfectly clean.

I bought an engine that was a 'supposed rebuild' from a local mechanic. After a year of trouble-shooting , I found out that the top end was done, then it spun a bearing, and he just did the bottom end, and sold it to me. Cylinders were scored due to the debris left from the bearing. I was so pi$$ed I ended up selling it as a core.

You don't want to go through the expense of a rebuilt, if remaining metal bits are going to trash the new engine.

alniki · 06-21-2009, 06:42 PM

dad911, thanks! So you are talking about the 'external' oil cooler, yes, it should be cleaned together with the thermostat and oil line.
The internal oil cooler seems to be safe as the oil filter stands before it. I'd add an oil filter after the tank if possible, or is that what the 993 got? It looks so easy to kill an engine if some tiny metal or silicon particles find their way into the oil tank!!

alniki · 06-21-2009, 06:49 PM

dad911, I'm in a similar situation. The swap engine I got runs noisy, probably due to a spun bearing or damaged IMS gears, so I'm wondering if it's damaged after being connected to the dirty oil circulation ines of my car. BTW, I didn't do the swap myself though I did mention about cleaning the oil circulation system to the wrench, who thought it's not necessary...

Hugh R · 06-21-2009, 06:59 PM

Don't know the cars all that well, but couldn't you take the oil lines and the oil cooler and flush them several times with solvent? An oil cooler is just a bunch of tubing going back and forth with fins on the exterior, isn't it?

burgermeister · burgermeister's Garage

According to the diagram, it would be safe to re-use either cooler.

If it's the engine mounted cooler, the oil would have been filtered before getting to it, so no debris in there.

If it's the external cooler, whatever particulate is left in it will end up in the oil tank and then will get trapped in the filter before making it back to the engine, or drained out with the next oil change.

Superman · 06-22-2009, 02:27 PM

I've been told, several times, by several guys who should know, that when an engine fails, you throw the cooler away. The engine-mounted cooler. Sure, you can try to clean it. And then, most likely, it will release bits into your new main and rod bearings. You'd think it could be properly cleaned up, but it doesn't work that way. So I have been told. FWIW. These same people always seem to ask, when an oil cooler becomes available, whether it was in an engine that had a bearing failure. If the answer is yes, they consider it a junk cooler.

docrodg · 06-22-2009, 02:31 PM

Remember... there is a bypass valve for the filter. plus, I would not trust that on the price of a whole engine.

My 1 cent: replace the cooler. not worth the risk. Then again, this sucks because new coolers are very expensive.

BAllen · 06-22-2009, 03:29 PM

Have the cooler hydro sonically cleaned. Ask cleaner to filter any shavings and let you know what if anything came out. If you race the car at all. Replace it. To much high RPM's How long did you run engine after the great big knocking sound from the back of the car. For a street car if the cooler came back with a clean bill of health, use it. Think about how many back yard mechanics just washed it out and put it back in service, then sold car. If there was a great failure why would anybody buy a used cooler ever.

alniki · 06-22-2009, 06:24 PM

Quote:

Originally Posted by Mo_Gearhead

You may get several opinions on this.

Mo-Gearhead was right!

Guess one should decide what to do based on his pocket and gambling instinct.

It limped about 0.4 miles, including a steep uphill, back to home, and finally died, could not be started again. Definitely a catastrophic failure but you see how enduring it was and how stupid I was, even tried to restart it. No other better choice anyway

s_morrison57 · 06-22-2009, 07:35 PM

I wound not chance it, evan if it delays the finish of a build I would wait for the budget to catch up with the new coolers, haven't heard of that sonic thing , might be worth checking out