JX7

I just had my downpipe installed a few weeks ago. Occasionally I get white smoke coming out of the downpipe side of the hood. I think it is coming out of my downpipe, but I never heard any leaks when I drive. The smoke smells like burnt exhaust (I think). It may also be coolant. I have no idea. This happens sometimes on startup or after a hard drive.

The downpipe itself is tight and I checked for leaks upon install. The car is running fine too. Any ideas what may be going on?

911GT2

If coolant leaks from the turbos coolant lines, it can run down the downpipe and burn off. This would create the smoke. Not a good thing.

After a hard drive, the downpipe would be hot enough to burn any coolant really quickly, so that explains that.

And after startup, coolant would have been leaking for a while, so anything thats on there will burn. So that explains that.

I'd say check the turbo coolant lines (these are prone to failure anyway, due to excessive heat produced by turbos).

JX7

Thanks for the help. Are you talking about the hoses that lead to the airbox?

Also do you have any tips on making this possible leak search easier?

badass7

Look at the coolant hose near the ABS unit going into the firewall. If they spring a leak there can easily shoot onto the downpipe. I had a pinhole leak on mine and also noticed a white smoke coming from that area before it got worse.

JX7

I checked that area. I'm having a hard time finding out where the smoke is coming from. If it is a pinhole leak, how can I find something so small?

r0t0r-rooter

Get a pressure tester and pump it up to ~17-19 psi. You'll see the drips if it's a coolant prob, and u'll also see the slow pressure drop. You can rent/borrow a tester from some auto parts stores w/a deposit. Be sure to get the import car adapter

legal-z

you might also want to check your rubber coupler on the top of the y-pipe. that piece is prone to leaking oil, especially after driving hard. the oil leaks down onto the y-pipe/turbos and burns off. i had the same problem you describe and it was the coupler. i replaced it with a silicone coupler.

DaedelGT

Take off your airpump and check the turbo coolant hoses.

LAracer

After I installed my dp I saw quite a bit of white smoke when it heated up. I was told that it was normal - that it was some residue on the pipe burning away (there should be a thread about this somewhere). After 3 or 4 good runs in the car the smoke went away, so I think that's what it is. This may be what's happening to you also, but if the smoke persists then check other things.

edit: here's that thread:

https://www.rx7club.com/forum/showth...downpipe+smoke

JX7

I have a silicone coupler on top of my y-pipe, but I think it may be loose. There has been a lot of wet fluid on top of my y-pipe and I'm pretty sure it's not supposed to be there. I'll retighten it and come back with the results.
Thanks for all the help guys.

areXseven

iTrader: (1)

JX7: When the DP is manufactured, the welds at the flanges and the Oxygen Sensor bung are usually spray painted. When the Dp gets hot, it will start to smoke in those areas because the paint is burning off.

Also, if you used alot of lubricant on the turbo female treads and on the studs, it will take some time to burn off and it will smoke. Good Luck. Hope it aint nothing serious.

LAracer

Yeah, that's what I was trying to say .

JX7

I don't think that is the problem because I've had my DP for 3 weeks now and the smell is just as strong.

areXseven

iTrader: (1)

Is the oxygen sensor on tight? Maybe it's leaking exhaust through there?

JX7

If the oxygen sensor was not on tight, I think I would hear a loud sound coming out of that area right?

GoRacer

iTrader: (2)

Check for o-ring failure. It could be steam from boiling coolant in overflow tank spilling out. This would be seen from the beetween the passenger fender and hood. Open radiator cap, turn on (cold) engine, look for champagne bubbles. Do you have an aftermarket water temp gauge?

If you actually seen the smoke from the DP, then retighten all the nuts. Try doing it while the engine is worm NOT HOT but warm since they will be easier to turn. If you still see smoke then did you replace the metal gasket when you installed the DP? If not replace. The nut are also disposable and not reuseable.

JX7

Hmm, I did not replace the metal gasket and I reused three of the nuts. But if that was the problem wouldn't I be hearing sounds from the DP area?
The engine is running fine so it can't be o-ring failure. Not to mention this problem only came since i put the DP on.

GoRacer

iTrader: (2)

^ noises, no not necessarily. Mine loosened up and to my surprise two studs and nuts fell off within a few months. Yes, I reused them. I also had an exhaust leak and also reused the gasket.

BigIslandSevens

iTrader: (4)

I don't remember what it's called but pep-boys, autozone,etc.. should have it. It is a dye that you add to your cooling system. you run the car for a while and shine a blacklight,(usually included in the kit) around the coolant lines. any leeks will show up glowing under the black light. cool stuff makes tracking down pinhole leaks alot easier. I think i saw it on two guys garage or some show like that. My theory on leak location would be one of the 2 coolant lines on the turbos, or the heater hoses at the firewall. good luck!! let us know what it is called if you find it before me.