It turns out that the crack is bigger than expected and I have to replace it myself, which manifold do I have to buy right or left (front manifold is cracked) and what is the other gasket I need to get besides the manifold gasket?

Left side = front of engine (toward front of vehicle)
right side = back of engine (toward back of vehicle)

There is a round exhaust gasket that connects between this piece shown below in the photo to the pipe that holds the front precat.

I believe in this diagram it would be piece 13, http://www.trademotion.com/partlocat...layCatalogid=0

alright, thank you. from what i can see all the work can be done from the hood and jacking the car up is not required, right?

Look at the picture and note the oil filter. If you have changed the filter, you would know the issue of clearance(s). The exhaust nut/bolts tend to bind and at times have to be chiseled off (just be prepared).

With the radiator in place, and my large hands, I would think twice before embarking on it as DIY.

Just think it through.

Salim

I'll second that. Sometimes those exhaust bolts can be a major PITA to get off and one sometimes needs some help. I figure if one bolt starts to become a problem, might be easier for an exhaust place to try to get it out. Same would go for an A/F sensor bung.

exhaust shops around here will charge a couple hundred just for labor... i do have a jack and stands, so i could lift the car if clearances become an issue.

There are times that mechanics fleece the customer but at there can be legit reasons to charge based on hours of labor. Check with couple of shops and ask them to break-down the charge, instead of a lump sum.

The rule of DIY is to know your limits (based on tools and accessibility). <= lesson learned over time.

Salim

In the life of my 1999 RX300 I had the Y pipe replaced under warranty and both manifolds replaced on my dime due to cracks. Common problem.

I do have an air compressor and air powered tools, I am going to soak the bolts with a 50/50 ATF - acetone mix. If it fails then I guess I have no choice but to have a mechanic do it.

woooooo.. success, took two people, a couple of hours, and some PB Blast, but the new manifold is in.

Nice, it took me and my in-law the similiar amount of time to get the manifold header replaced on the Acura. Just patience and loosening and tighting bolts...

So my Lexus cats were clogged. Recently got the cats hollowed. Check engine light is on(to be expected) but car is still lacking in throttle response like there's no back pressure. I'm going to reset the Ecu, but I can smell how rich the gas flow is, and Milage is horrible. Could the exhaust manifold be cracked or is it lacking in performance because the cats are hollow? What could this be and what should I check?

Welcome to the Club.

I'm not going to get into the legalities of this, just the mechanics.

Lacking in performance because the cats are hollow is the answer and that light is due to lack of a main cat underneath, likely a P0420 and possibly with a P0171 with it.

Realistically, the only way it's going to work with hollow cats is if you get something like forced induction or at least the bare minimum a ram air system like I have with my RX300. Not enough input = not enough output.

Basically, gas is just passing through the system without being burned and sucked out the back. If you hear any popping noise, that's a symptom of that.

For example, the 5 speed first edition Toyota Solara has a 1MZFE engine similar to the RX300 with federal spec emissions with just a main cat underneath and neither of the two precats you have on your RX300, and does just fine for power even if you have a free flow exhaust on the end, something very common with our friends over at Solaraguy.