FORCED-INDUCTN

Hello,

Long story short: my RX7 is leaking from the rear of the intake manifold. I've taken the manifold off the car and cleaned up the area in an attempt to identify where the leak is. I have attached some picture that will hopefully help.

Long story:
I recently purchased a 1986 N/A M/T RX7. I payed a legitimately low sum of money for the car, knowing that it had some issues and was not in the best condition. My long term goal is to swap in the S5 TII engine, subframe, and trans that are sitting in my garage But I need to get the car running well enough to smog and it would be nice to drive it around as-is for now.

When I got the car home from my Craigslist rendezvous, the coolant buzzer started going off. I checked for coolant and there didn't appear to be much in the car although I could hear it bubbling around in the engine. I filled the car up and it immediately started leaking from the water pump weep hole. So I tore down the front of the engine and replaced the water pump. All was good for a week and a few drives and then the coolant buzzer went off when I was down the street at the store. I took the car back home and when I parked the car I got a little bit of steam coming from under the hood. I poked around a noticed the (new?) coolant leak around the bottom rear of the intake manifold.

I could not get a good picture of the leak when the car was together but basically the water appeared to be dripping onto the exhaust manifold from the area around the bottom rear intake manifold bolt. I assume the leak is actually more central to the manifold and the coolant was just flowing along the bottom of the manifold.

Picture of the area before cleaning:
http://twh.invadethenight.net/overview_dirty.jpg

Rear housing seam before cleaning:
http://twh.invadethenight.net/Rear_h...seam_dirty.jpg

Right housing and a plug that I assume blocks the passage used by the turbo cars?
http://twh.invadethenight.net/plug_a...seam_dirty.jpg

Not sure what this port is for but it doesn't look right:
http://twh.invadethenight.net/port_dirty.jpg

Everything when somewhat cleaned:
http://twh.invadethenight.net/clean_overview.jpg

Seams and plugs when clean:
http://twh.invadethenight.net/clean_seams_and_plug.jpg

Port thing when "clean" appears to be some kind of sealant in there:
http://twh.invadethenight.net/port_clean.jpg

Beautiful mint condition-nearly-new lower intake gasket
http://twh.invadethenight.net/manifold_gasket.jpg

Did I mention the car has a lot of miles on it? About 232,000. You're welcome to laugh at all the sand pilled up above the intake ports ...and all the gunk in the intake runners, I'll clean all that up!

So any ideas which suspicious location is my culprit? The blocked port above the intake ports looks bad for sure. Later tonight or tomorrow I'll fill it up with coolant and see if I can get any to come out but I suspect I'll need a leak test to do that.

Thanks in advance!

--Will

littlebit421

When you removed the lower intake manifold did coolant come pouring out?

Aaron Cake

iTrader: (1)

Around the rear of the intake manifold on the S4 NAs there are several coolant lines that feed a thermowax plunger which nudges the throttle open a bit on cold start. Those lines start on a nipple at the rear iron, loop around the intake connecting to the thermowax and BAC, then end at the water pump housing. Bet that one of those lines is leaking, or the thermowax itself.

FORCED-INDUCTN

Hey Guys,

Thanks for the quick responses! I fell asleep when I get home but figured I'd do some late night work

@littlebit421 Nope, no coolant poured out when I removed the manifold. Although quite a lot of coolant had already dripped out of the engine. From my basic testing the coolant doesn't appear to start leaking until I start the engine. The engine doesn't even have to warm up much before the dripping starts. Although the dripping does continue for a while after I shut off the engine, at least that's what the large puddle under the car tells me.

@Aaron Cake, I initially suspected the vertical coolant line that comes from rear iron up to the thermowax as it had a small split in the end that slipped over the thermowax nippple. I did replace this line but the leak persisted. I should also mention that I removed the thermowax (and the upper intake manifold) to test it (idle/warmup issues) just before the engine started leaking so there is a possibility when I cleaned it I caused it to leak. I did try to inspect around the thermowax and verticle coolant line while the engine was running/leaking and I don't remember seeing any coolant come form the upper manifold but maybe I just missed it. I'll pull all the thermowax/BAC coolant lines and inspect/replace them. I'll also try to get some pictures of the thermowax and look it over for signs of leakage.

(P.S. I love your YouTube channel Aaron, sorry to hear about the break in)

Thanks!

--Will

Aaron Cake

iTrader: (1)

Unless you are leaking between the iron and housing, based on the area described, it can really only be those coolant lines. What you might have to do is perform a cooling system pressure test so that the system and be pressurised with the engine cold. Will be easier to spot the leak. Hopefully not between the housing/iron.

FORCED-INDUCTN

Sorry for the super delayed response. I'm mostly posting this for anyone who runs into the same issue. After a lot of inspection (and many interruptions) my roommate and I determined that the discoloration in the water jacket plugs was actually a "water mark" where coolant was leaking out of the jacket and pooling inside the plug pocket. I mixed up some J-B Weld and applied a decent coating to the plug area. Reinstalled the intake manifolds with new gaskets and I haven't lost a drop for about two months. I recently discovered the first catalytic converter was clogged so the potentially elevated EGTs and leaking water pump probably contributed to the cracking water jacket/plugs (damage done by the previous owner).

Thanks for all the help Guys!