NanaimoRx-7

I had an exhaust leak start late last summer on my '93 RHD 7, so I ordered up new gaskets and took the twins off for my first time. It wasn't fully obvious where the leak was coming from, I thought it was from the secondary turbo gasket but it was dirty around the manifold to engine block as well so I replaced all the gaskets from the block out.

Did a test start once the downpipe was back on, still leaking. Took it all apart again and re-read a bunch of threads on the forum, I noticed that I under torqued the nuts on the turbo exhaust brick to the stud tightening torque listed in the FSM. Figuring this was my mistake I worked my way back out to the downpipe again. Test Start. Leak. Swear. By this time the snow was starting to fall and my driveway wrenching days were over for the season so I put it all back together for the winter.

Fast forward to the spring, I've been driving the car a little. I definitely wanted the leak to be more obvious this time. So I took it apart again, now I know for sure where it's leaking from I'm just not sure how to proceed. It is leaking from the secondary gasket along the top and a small one in the bottom. I see some pitting on the manifold surface I don't know if that's causing the leak or if it's because I wasn't able to separate the nuts from most of the double end studs.

When I was putting it together I only had one stud mounted into the manifold for each gasket, then once the turbos were in place I put the center bolts in and worked my way out I think I tried to double nut the studs into the manifold but there's a really good chance I didn't bring the surfaces together in a very even fashion.



Original Vs Replacement Gaskets



So now I have replacement studs (not OEM) from this thread https://www.rx7club.com/3rd-generati...dition-957371/ and I'm ready to try again. I have a spare stock turbo exhaust brick and a set of old turbos.I don't know if I should try to separate the turbos form the center section, port the wastegate and use the spare manifold. Or if I should just swap the manifold and mount the studs properly and try again.

I'm hesitant to split the turbos because they're in good condition (very little play and no smoke) but I also have a mid-pipe with a hi-flow cat that I want to install so maybe I'm already committed to removing a turbo to do the porting? I need some advice.

George

IRPerformance

iTrader: (41)

Did you put a straight edge to the manifold to see if it was warped? Also, it is possible that the turbos are clocked wrong. Loosen all the bolts around the chras, then tighten them against a manifold, then tighten the bolts up.

DaleClark

iTrader: (55)

The manifold to turbo flanges don't look like they are leaking. You typically see a trail of black soot wherever the leak is. There is some sort of black sooty-ness under the heat shield on the turbos themselves in one of the pics, that might be worth pulling the shield and investigating. Sometimes the 13mm bolts that hold the CHRA to the turbine housing come loose or missing and cause a leak.

Dale

NanaimoRx-7

I'll pull everything off for a closer look and run a straight edge across all the surfaces to see if something has warped. It was perfect for the first 3 months I owned it, actually it was too quiet with just a cat-back and it was weird not having to change my shirt after a long drive. Never had a 7 with a cat before lol. I like the idea of bolting it together off of the car maybe I can see what's going on between the mounting surfaces.

IRPerformance

iTrader: (41)

I've also had a bolt back out of the turbine housing causing a leak. Took a while to find.

NanaimoRx-7

I'm thinking that this is the problem area, it looks like the manifold has a slight warp. I think I'm going to try using my spare manifold and see if it seals a little better than this.

NanaimoRx-7

I took the heat shield off and had a good look around the turbos, no easy missing/loose bolt and no signs of carbon buildup on the turbos or the underside of the heat shield.

DaleClark

iTrader: (55)

Those manifold to engine gaskets tell the story, that's your leak right there. The hot blue on the inside going to the soot on the outside, that's a leak all day long.

Could be something on the engine that's keeping the brick from sitting flat on the engine. I doubt the brick could be THAT off. Time for a straightedge.

Dale

NanaimoRx-7

Well Dale it looks like you were right, I tried the spare brick and put it back together as far as the downpipe and gave it a test start, still leaking. I already had the turbos back on before I saw your post so I decided to at least give it a go with the spare manifold. So if it is on the engine side what options do I have left? I don't understand how the engine block could come out of alignment after 4 months of being perfectly sealed. Let's say than pulling the entire engine is probably out of the question at this time, I don't have the funds for a rebuild while we're saving for a house downpayment.

Would I be crazy to try flipping the gaskets or doubling up on them with a copper sealer in between? I'm going back to work so it will be another 8-10 days before I can get out there and fiddle with it again, I'll also need to buy a smaller straight edge to fit down there to check the block. I'm used to the 1st gen world where there's always some crazy way to make it work, I'm open to any suggestions.

George

K-Tune

iTrader: (26)

I doubt very much that it's the engine itself causing the leak, unless the exhaust sleeves have somehow shifted out of place.

Did you happen to take a picture of the manifold where it attaches to the engine?

DaleClark

iTrader: (55)

I've also seen aggressively-applied RTV oozing out of the gap between the housings that could cause an exhaust leak.

Basically you need to straightedge everything. At least you know which flange it's leaking at.

Dale

NanaimoRx-7

So I dug up the photos I took in the fall off my old phone and I don't like what I see. I noticed that gap around the edge of the sleeve this time and I did get in there with my hands to see if it was loose but I couldn't budge the sleeve at all. I guess I figured it was normal but I didn't think to put the gaskets up against the motor to see just where that gap would end up. Looking over my old pictures from the first time I'm getting a bad feeling that this is my problem.

IRPerformance

iTrader: (41)

The sleeves should not move. The are held in by roll pins from each side of the rotor housings and cannot be removed properly without disassembling the engine. Clean the entire mating surface of the rotor housings and see if that helps. I'd also get that manifold faced.

Speed of light

iTrader: (8)

Yep. ^^^What he said. You might want to use a real machinist's straightedge, square or ground parallel (for maximum flatness) and try putting some very thin feeler gauges, e.g., .005" or less, under at different spots--and/or at least put a strong light source behind the straight edge and eyeball it real good--that being said, it wouldn't necessarily need to be a big gap in there, rather; it could just be a high spot that is preventing the manifold from fully seating flat and evenly compressing the gaskets. Have you held the manifold to the engine without the gaskets to see if feels like it's sitting flat or if rocks around or seems high-centered? Attention to detail is key here. Look hard enough and I'm sure you'll find the culprit. Btw, are you able to apply and hold full torque on each of the manifold studs?

From your pics, it sure looks like there's possibly something going on at the front housing/center plate junction. It doesn't appear [to me] that the exhaust gasket's sealing bead is seating on the front housing in the area near the center plate; the same condition is mirrored on the exhaust manifold as well.

NanaimoRx-7

Progress has been slow lately, trying to get the 3 W's to cooperate; work, wife and weather. I was able to get a local machine shop to deck the manifold, think the guy said he took about 0.010" off the engine side and slightly less on the turbo side. Another week and I'll have some time to bolt it all back up. I have noticed that the centre housing does have a little lip on it, not sure if it's going to be an issue. I'm hesitant to get in there with a grinder, next time I'm at the car I'll line up some feeler gauges and measure the lip.

DaleClark

iTrader: (55)

Who would have thought ground down cast iron could be so pretty?

Hope to hear of good results soon!

Dale