artic94

hey guys I have a 94 z28 having a oil leak from the looks of it coming down back of the block could this be the intake leaking and if so what is the easiest way to remedy this problem thanks in advance

Injuneer

The rear of the intake manifold, on the passenger side, is a common location for an oil leak. However, there are other possibilities, including the oil pressure sensor (located there on most 94's, but not the ones produced very early in the model year), valve cover gasket, and even (although it's hard for me to understand how) the corner of the head gasket.

As noted, check the passenger side of the rear of the block for drips. Take a paper towel, reach back over the edge of the manifold, and wipe the block to see if there is an oil buildup. The oil pressure sensor is more toward the driver side of the block, immediately behind the edge of the manifold.

I would try and pin the location of the leak down a bit closer, before determining the required fix.

Shoebox has some great photos of the back of the manifold. As mentioned, the early 94's have the oil pressure sensor on the driver's side of the block, right above the oil filter.

4th Gen LT1 F-Body Tech Aids

http://shbox.com/1/oil_pressure_sensor.jpg

In the photo, you can see the orange RTV used to seal the manifold to the rear wall of the block.

artic94

ok ill check it out it seemed like the oil was coming down more along the passenger side judging my the few drips left on the garage floor

Injuneer

Some people speculate that heat from the corrugated EGR riser pipe cooks the RTV in that area of the manifold, and it starts to leak on the passenger side.

artic94

lets say it was the gaskets how hard is it to change them

artic94

I have heard that from a few people I was told by a friend that he had a 95 had just over 30k on it had to get the intake gaskets replaced

Injuneer

Like I said - common problem. I never had it in the 80K miles on my 94, neither the factory install, or the reinstall when we put the LT4 intake on the stroker.

The area that leaks does not have a gasket. Only the intake port areas are gasketed. The "china wall" as it is known requires a bead of high temp, sensor safe RTV to be placed on top of the block, the manifold lowered very carefully in a straight line using dowels, bolts torqued in correct sequence in two steps, then a mandatory 24-hour curing period before the engine is started.

Shoebox covers the removal and install as part of his cam swap procedures:

4th Gen LT1 F-body Cam Removal

4th Gen LT1 F-body Cam Install

artic94

ok thanks also another quick question

I went to turn on my rear defogger the light comes in on the switch but back window doesn't unfog or anything any ideas

artic94

and also with the water pump being cam driven it is normal to get warmer air from vents while cruising down the interstate rather than putting around or at an idle correct?

Injuneer

Generally best to start a new topic for each unrelated problem.

Generally means there is a problem with the 30amp circuit breaker for the rear defroster (also powers power seats if you have them). Located in the panel at the end of the dash.

The fact that the water pump is driven off the cam, instead of a belt off the crank, has little if anything to do with the water flow through the system. Water flow is proportional to engine RPM, and whether the pump is driven off a gear on the cam sprocket, or by a belt off the crank does not change that.

The LT1 cooling system constantly flows water through the heater core - there is no shutoff valve. There is a "flow control valve" which is basically a restriction orifice, to limit flow through the heater core. The flow of air through the heater core, into various ducts, is controlled by the dash panel HVAC control, using vacuum from the engine.

Sounds like the flapper doors that control flow through the vents are in the wrong position. Might want to check the vacuum line from the passenger side of the intake manifold to the vacuum check valve, then into a wire bundle that goes through the firewall. If you have a vacuum leak in that line or the check valve, the doors will move to default positions. The check valve is a common failure item:

http://shbox.com/1/vac_check_valve.jpg

http://shbox.com/1/hvac_vacuum.jpg

artic94

that would mean the seat wouldn't work correct?

Injuneer

If it's a power seat it wouldn't work.

artic94

yea its powered and it works fine I was confusaed as too why the light on the switch comes on but not working at the window

Injuneer

I would recommend you download the 94 F-Body factory shop manual. The electronics for the rear defogger are mostly contained within the switch assembly - illumination lamp, "on" lamp, relay, solid state timer and the switch. Complicating the issue is that the Camaro and Firebird systems operate differently.

You can get a free download of the 94 manual here:

LINK: 4TH GEN SERVICE MANUALS - Firebird Nation

The rear defogger section starts with the Camaro wiring diagram in Volume 2, page 8A-61-0

artic94

ok thanks a bunch