Return now to the junction of the walkways and drop down to the walkway below - mind the SkaarjWarrior on patrol here. Read the information panel nearby.
"WARNING: ENGINE COOLANT LEAK ON LOWERMOST FLOOR OF THIS AREA."
Well, the engine coolant leak is probably worth investigating. So, you need to go back and get that Toxin Suit you left all the way back in cooling system control. Argh.
So, climb the ramp and follow the corridor towards the blue zappy generator. Walk beneath the zappy bit - you'll be fine as long as you don't jump - and go through to the lift shaft at the far end. Collect the two ASMD Cores here, then press the button to call the lift. Ride it all the way to the top and open the doors.
You can find your own way from here; cross the ship and enter cooling systems control. Enter the room on the left and collect the Toxin Suit from behind the far pillar. When you're done, return to the coolant leak in the containment field generator area.
Drop into the gunge and go through the opening in the wall to a low-ceilinged area. A SkaarjScout guards some corpses here; kill the Skaarj then read the information panel nearby.
"CONTAINMENT ENERGY CORES EXTREMELY VOLATILE: ALL WEAPONS MUST BE PLACED ON SAFETY."
There's a lift at the far side of this area; ride it up and collect the Assault Vest in the ducting at the top, then turn left on to the uppermost level of the lower generator area. While the area above the core to the left is empty, the area above the other cores has 4 Health Packs for your attention.
Anyway, you've cleared this area, so where now? Main engineering should be accessible now, so use your knowledge of the ship to return to the main corridors. Turn right in the corridors to so that you arrive at the main engineering lift. Go up the lift, and you will see that the force field has gone and the information panel has changed.
"MAIN ENGINEERING: INTRUDERS DETECTED PROCEED WITH CAUTION."
At this juncture you will probably be seen by a SkaarjGunner armed with a Dispersion Pistol operating the consoles within. Kill it, then enter engineering yourself.