'97 motor in '98 car -- oil pump plug
 

My '98 Spec Boxster's motor died at the track last year, and I bought a good used '97 motor from a friend while I have the old one diagnosed. Moving accessory parts from the old to the new.

There are a few interesting differences in the '97 and '98 engine blocks. The oil cooler interface is one, and I've used the Porsche adapter plate to put a new '98+/ S/996 taller oil cooler on the '97 block, which does not expect the flat-bottomed plate of the '98+ oil coolers (it expects two of the feeds protruding and extending into holes in the '97 block -- the adapter plate provides these). The '98+ oil coolers also have a vent line nipple and a hose leading to the coolant tank. The '97 block instead has a hard line coming off the oil pump housing that I believe is for the same purpose, to vent air bubbles from the water lines at the highest point on the engine -- which it turned out is actually the oil cooler, so they changed it post-'97.

My understanding is that these serve the same purpose. I supposed I could "Y" the lines together. Or, perhaps better, there is a Porsche part 99610711900 "stopper" that would appear to block off the vent line opening on the '97 vent line opening on the oil pump housing. This seems like the best option -- but I can't tell how to remove the line there in order to replace it with the stopper plug. Any ideas?

Attached photo -- red arrow points to the '97 vent line location top front of oil pump housing, yellow arrow points to the vent hose coming off the oil cooler. The first one does not exist on '98+ engine blocks -- the oil pump housing has no opening there, it's just flat. Removing and plugging that line is the idea here.

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When I put a newer oil cooler on a '97, I put a hose on the bleeder outlet of the cooler and plugged it with an appropriate sized bolt and hose clamp. I connected the tube from the oil pump housing to the tube on the tank.

In your case, if you want to eliminate the connection on the oil pump housing all together, why don't you take the housing off the bad '98 engine and put it on the '97 engine?

...meanwhile, I'll pull the oil pump housing off my dead '97 engine and get a look at that tube. It shouldn't take long and I'm curious.

The tube from the oil pump housing is bolted in two places; vacuum reservoir and the face of the housing by the tube. I thought it would come off with the standard 'push the plastic ring in and pull the tube out' method, but mine didn't. It did come off with moderate pulling force while rocking it back and forth on top of the engine - and the plastic piece broke or was already broken.

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Thanks, that's great info.

I had considered swapping the oil pump housing from the 98 to the 97. Might still do. But it's an entire assembly -- unfortunately that little cover panel of interest is not a separate thing!

If you don't see another way to get the line out other than force, maybe I'll try that, see if the plastic clip breaks, and see if the plug would go in and seal it or not. Worst case: swap the whole oil pump housing as mentioned. Some else said to me "just weld it closed". Maybe...

In my web search results, I found your post where you had removed a 98+ oil pump / housing -- sounds like that was not hard to do. Do you still have that item to sell, if it's worth considering for this job?

I've had one in sitting a box for a few years. I'll find it tomorrow and make sure it looks good. I pulled it off a 2001 2.7L engine, but pretty sure it fits the same.

Aha! After many minutes of searching the technical manual I found where the "coolant guide housing" contraption is discussed. The line *should* come off with the standard "push the plastic ring in and pull the line out" procedure that you mention. (Step 1 in the diagram.) Sounds similar to detaching the power steering line coming off the back of the PS unit, which I have done twice recently. I'll give it a try. This should allow me to simply insert the stopper plug in place of the vent line.

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Awesome. Hopefully the plug comes with a new plastic unlocking ring. ... just in case.

coolant vent plug installed
 

The coolant vent plug part arrived and I was able to remove the hard line and install the plug.

- removed two 10mm bolts that fastened the hard line to the engine block; one on top and one next to the hole
- pushed the black plastic ring in, wiggled and rotated the hard line, hoped nothing would break, and eventually it moved and slid out; nothing broke, yay!
- pushed the ($20!) plug into place

Hopefully we'll get the engine installed tomorrow or the following weekend, and all will work as normal.

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