JW89225

Hi Rennlister,

Recently caught intermixing in the 3.4L. Noticed the oil level dropping suddenly last week, decided to top up and monitor. Noticed the oil filler cap was sucked shut. Found the milkshake inside the tube and cap when I eventually got it to open. Checked the coolant tank and sure enough, milk shake. Mechanic determined indeed oil in coolant and some coolant in oil?

-No smoke, no CEL, no misfire
-Oil cap is tight (vacuumed shut)
-No leaks
-Temperature has been stable, always at 180 mark: short drive, long drive. Low & high rev.

I'm thinking head cracked and/or oil cooler failure.

The plan is to flush, clean out the gunk, drop the engine and determine which of the two. Am I missing anything here?

Car is a 1999 Carrera 131,000 miles.

yelcab

A third possibility is a cracked cylinder. Time to disassemble and investigate.

Charles Navarro

It's unlikely to be a bad oil cooler. Only seen one failure in all these years.

Did the engine have a water pump failure and subsequent failure that you are aware of? Usually the heads will crack 6-9 months after a water pump fails. Like Yelcab mentioned, cracked cylinder is likely the cause of the intermix if the water pump hasn't failed previously. If the water pump happens to be original to the car, I'd recommend pulling it to see if the impeller has come apart.

JW89225

It was last changed 4 years ago along with thermostat. What are the symptoms of failed water pump? I just recall temperature always sits at 180 over the zero.

I don't recall overheating but sounds like I should start looking for a replacement engine rather than repairing?

Charles Navarro

The impeller will start coming apart. Little bits of plastic then get embedded in the coolant passages in the heads and they crack. It's not necessary to overheat the engine to have the heads or cylinders crack.

it's quite possible it took this long for a piece of plastic to end up somewhere it shouldn't have been, but being four years since the pump was replaced, unless the car hasn't been driven much, it's probably not a cracked head caused by water pump failure debris.

It may be possible to pressurize the cooling system and inspect each cylinder with a bore scope to see if you can see coolant entering the cylinder.

Putting in a used engine is going to be a crap shoot. The best option will be to rebuild it. Cracked cylinder is no problem. Block can be sleeved and you can bump the displacement at the same time to 3.8 liters. If it is a cracked head, I would avoid any repairs with welding and just seek out a good used head that can be pressure tested and rebuilt.

JW89225

Car sat mostly for 2 years during covid, and driven daily during the past 2. In this case, how involved is rebuilding/re-sleeving back to a factory 3.4L assuming other things are ok internally ie: heads etc.

Charles Navarro

There are many other DIY guys that have tackled a rebuild of their 996 engine without any prior experience as long as they were mechanically inclined. Along with a few specialty tools, you'll want the Focus on M9X dvd series which will go over in detail every step of the rebuild process:

https://lnengineering.com/focus-on-m...embly-dvd.html

Considering the cost and effort, there is no reason to build the engine back to stock size as there is no added cost to go bigger (3.8 liters in your case). This page summarizes the process and options:

https://lnengineering.com/products/w...e-scoring.html

pdxmotorhead

If you get in to a rebuild, there is no good reason NOT to go 3.8 , the sleeving process you can see on various videos on line from Both LN engineering and Hartech.
Its a BIG process.. Not a overbore and a pressed in sleeve.. I had mine done 3.8 and love it. (I had a 3.6) More torque is always good..