You may recall a few posts ago that I was having issues with coolant leaks on the MR2 Spyder. I had previously replaced several leaky rubber plugs along the side of the head and the thermostat bypass pipe. While they certainly weren’t easy to get to, they were still accessible from the engine compartment. Unfortunately, I had traced this latest leak from up under the intake manifold, impossible to get to with the engine in the car. I was left with two options; either remove the engine or cut an access hole in the firewall. I’ve removed this engine numerous times, and it wasn’t something I looked forward to doing again. While I didn’t really relish the idea of cutting through the firewall, the benefits swayed my opinion. It would provide access, not only for this current issue, but any future work I would need to accomplish on the cold side of the engine. Through the firewall I can now reach the alternator, thermostat, starter motor, intake manifold, throttle body, and several sensors such as the knock sensor.

First things first, estimating how large the hole needed to be and removing the sound deadening mat.

Firewall Access 1 Firewall Access 2

Now for the first in a series of cuts. I used a pneumatic cutoff wheel and air sabre saw, which cut right trough the thin sheet metal with ease.

Firewall Access 3 Firewall Access 4

I cut away a small bit at a time, realizing that the hole must be much larger to completely remove the intake manifold.  I also used a 1″ hole saw to drill an access hole for the large bolt that secures the lower end of the intake manifold to the block.

Firewall Access 5 Intake Manifold Lower Bolt

With the hole large enough, I was able to mark the various vacuum lines for removal, as well as the TPS and IACV plugs and the throttle cable.

IMG_7011 Intake Manifold Removed

Now to get to that leak.  Even with the manifold removed it was difficult to access.  I had to use several extensions and u-joints to remove the bypass pipe, then a pry bar to squeeze it out from behind the crank-case vent tube.  Finally with the tube out you can see how deteriorated the rubber plug is.

Spotting the Leak Leaking Plug

While removing the intake manifold, the VVT solenoid was accidentally stripped from its wires.  Fortunately I kept all the old plugs with pigtails from a couple of old engine harnesses, so I had the exact plug needed.  The wire colors were different, but a quick check with the wiring diagrams confirmed the positive and negative leads.  I soldered the new plug and covered it with heat shrink and electrical tape.  The extra length of wire will hopefully prevent it from getting pulled out again.  Also, don’t forget to replace the bypass pipe gasket before reinstalling.  By the book it’s considered a one-time use part.

VVT Solenoid Plug New Bypass Pipe Gasket

It was a good thing I removed the intake manifold, because I discovered another completely deteriorated plug on the intake manifold. This one isn’t for coolant, but it would have definitely leaked boost and caused the engine to run poorly.  Finally everything back together.

Cracked Intake Plug Intake Manifold Installed

After reassembling everything I bled the coolant system again, then fired up the engine to check for leaks. I ran the engine until the thermostat was fully open, then let it cool over night and checked the coolant level the following day. So far no leaks, so I decided to run it again and stress it as much as possible (difficult to do without a load on the engine.) I ran the AC on full, covered the radiator with a towel, and kept the revs up to 6k with my hand on the throttle body, watching the oil and water temps the whole time. The car ran cool and no leaks, even with no air circulating over the radiators. So far so good, but the real test remains; taking it to the track.

Now I’m left with a gaping hole in the firewall, so the next step will be building a removable patch panel. More on that later.


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