Superblack Has "Gas"

[AttyDallas (Paul L.)]

@JimD_in_Alabama

Sounds like the secondary air. Does each round pipe have 6 little pipes going down and into the inlet manifold. On my picture the fuel rail is red (thank you SD Faircloth) and the secondary air rail is gray metal

Oops - I was thinking those were for air and not radiator coolant … : goofed there! Thanks for posting that (btw, so should either of them feel warm for any reason?)

[AttyDallas (Paul L.)]

@sbobev

The secondary air-injection is an ancillary system, in place to help the catalytic converters light up (reach operation temperature) quickly. After 2-3 minutes, the system is just added weight.

However, I can envision a situation where they could get very hot.
There are one-way check valves at the end, buried between the engine and the firewall. They could be rusted and not functioning, which means that small exhaust leak could be happening and making the tubes feel “hotter”.

EDIT: The check valves should only allow flow from the pump to the exhaust manifold and not backwards. Item #6 (one for each rail)

Ut oh … Steve, just now read your post after posting that earlier response - yes, sounds like something that needs to be checked out, then … thanks

[AttyDallas (Paul L.)]

@gregma

luckily mine is an 88 with the 16CU. So no such thing as a CEL.

I find that ridiculous that they still require smog checks for cars this old. Our state of WA made a bold and smart move, no more smog checks starting this year. (Before this, it was no smog if your car was 25 years old, or if your car was manufactured after 2010.)

Reasoning? All cars built after 2010 are very smog compliant, and it’s almost impossible to tamper with. So no need to test them. And now, in 2020, the vast majority of cars are 2010 or newer. Even cars built in the 90s through 2010 are quite smog compliant. The amount of cars like ours that put out excess smog are such a drop in the bucket, both in volume of cars and amount of pollution, it is not worth spending the money testing them.

Yep, that’s what TX has done (no emissions requirement for cars 25+ years old) … That’s how Superblue finally squeaked in and probably the same situation for Superblack. In fact, I guess if I wanted I could remove the cats and get better HP (?)

[JimD_in_Alabama (JimD in Alabama, 95 V12 XJS Coupe, Marelli, LHD)]

Warm? Suppose so. Thermal conduction from other things they touch
Not hot.

[gregma (Greg (1988 XJ-S V12 Lucas))]

Removing cats barely does anything. Removing mid mufflers (the big ones under rear seats), wow! What a difference in power! Sounds goes from silence to normal car sound.

[AttyDallas (Paul L.)]

Well, by way of update, Superblack is no longer blowing anything (visible) out the pipes … Phew! Another potential issue down, another 2356 only to go …

[SD_Faircloth]

Never really understood your concern. The article I added before indicates that (IIRC) 13 % of exhaust gas is H2O…water. If the engine, cats, exhaust pipes, mufflers are cold…the water will blow right thru and drip out. As all those items begin to warm up, the water eventually vaporizes. My Yukon does this all the time. SD Faircloth

[AttyDallas (Paul L.)]

What was worrying me was that it was doing it still 15 minutes+ after start up, which I would not think is the norm, but then I have never had a 5.3 before. Superblue doesn’t do that – just her brief cloud of blue smoke upon startup after sitting a few hours …

[gregma (Greg (1988 XJ-S V12 Lucas))]

15 minutes is a bit long, how is the fuel? All new gas? Old gas will have water in it.

Also, check the coolant and make sure it’s not decreasing, which would point to head gasket.

[davidsxj6 (David)]

@gregma

Old gas will have water in it.

Nowhere near enough to make a difference. Burned gas is partly water… 13% actually sounds low!
As long as the complete exhaust hasn’t been burning hot for a while there is no way all the condensation has steamed out - but mostly the vapour must be condensation from the still cold pipes. It will take a long time to warm up - ten minutes while driving is standard for most normal cars?
Invest the time spent worrying towards learning what all the wires and hoses under the bonnet do - you’ll do great! And teach your tech, too. Also you might want to empty the tank and fill it with fresh gas soon if you expect anything: new filter, too.

[AttyDallas (Paul L.)]

@gregma

15 minutes is a bit long, how is the fuel? All new gas? Old gas will have water in it.

Also, check the coolant and make sure it’s not decreasing, which would point to head gasket.

Well, as I posted earlier, it isn’t doing it anymore, so apparently it was condensation (water) in the fuel. I guess that 1/2 bottle of STA-BIL stuff I put in 2-3 weeks ago when I added some premium fuel did a good job in removing it although actually it touts itself as a “fuel stabilizer” and “fuel system cleaner” (vs., e.g., Heet, which is specifically to remove water). Phew!

[AttyDallas (Paul L.)]

@davidsxj6

@gregma

Old gas will have water in it.

Nowhere near enough to make a difference. Burned gas is partly water… 13% actually sounds low!
As long as the complete exhaust hasn’t been burning hot for a while there is no way all the condensation has steamed out - but mostly the vapour must be condensation from the still cold pipes. It will take a long time to warm up - ten minutes while driving is standard for most normal cars?
Invest the time spent worrying towards learning what all the wires and hoses under the bonnet do - you’ll do great! And teach your tech, too. Also you might want to empty the tank and fill it with fresh gas soon if you expect anything: new filter, too.

Good point about the fuel filter, and glad it is so accessible on our XJSes (i.e. on outside of car). I can’t decide whether though to change it now, before the first tank of (old) fuel goes through her, or wait til that tankful is gone and before I start putting in her first fresh tankful (or maybe both – they’re cheap, under $10).

[AttyDallas (Paul L.)]

@AttyDallas

@sbobev

The secondary air-injection is an ancillary system, in place to help the catalytic converters light up (reach operation temperature) quickly. After 2-3 minutes, the system is just added weight.

However, I can envision a situation where they could get very hot.
There are one-way check valves at the end, buried between the engine and the firewall. They could be rusted and not functioning, which means that small exhaust leak could be happening and making the tubes feel “hotter”.

EDIT: The check valves should only allow flow from the pump to the exhaust manifold and not backwards. Item #6 (one for each rail)

Ut oh … Steve, just now read your post after posting that earlier response - yes, sounds like something that needs to be checked out, then … thanks

Well, my tech and I revisited the “hot pipe” issue a couple of days ago, and it indeed is HOT on that side. Therefore, the check valve is apparently froze/rusted closed (or open?) from what someone suggested earlier on here. Very fortunately, I was able to find one last N.O.S. one on Ebay from an estate sale, and nabbed it for a mere $22.00. Only have to hope the driver’s side pipe doesn’t start doing ditto.

[davidsxj6 (David)]

Run down the tank if you want, but if all those additives do anything they will start in the tank and proceed in the filter before they go to the injectors just saying.
If the tank is low I‘d drain it if possible, use the gas in my other cars and flush the lines, then start with a fresh filter but that can wait as long as it still runs, why bother…

[Cadjag (Carl Hutchins, Jr.)]

Whikite condensation from a smooth pair of pipes looks nice to me!!!

Carl

[JimD_in_Alabama (JimD in Alabama, 95 V12 XJS Coupe, Marelli, LHD)]

Therefore, the check valve is apparently froze/rusted closed (or open?) from what someone suggested earlier on here. Very fortunately, I was able to find one last N.O.S. one on Ebay from an estate sale, and nabbed it for a mere $22.00. Only have to hope the driver’s side pipe doesn’t start doing ditto.

IIRC there is a GM or aftermarket check valve that is same and doesn’t break the bank. Check the archives… was in a post by Sbobev. When I cleaned out my rails I used the info from Steve. And plenty of powerblast and BF’ing wrench to separate the valve from the rail on one of the sides

[AttyDallas (Paul L.)]

Yep, I could see a LOT of elbow grease possibly needed on that task …