Recently had a few issues pop up after replacing a few things on my 2000 Honda Civic automatic (D16Y7). It's been sitting in my folks garage/drive way for several months now as I've been doing the repairs on random weekends.

Issues

1. Car begins cycling between low and high idle when it is warmed up, around 4-5 minutes after start. CEL was P0505 before I erased it two weeks ago. I only work on it during the weekend when I get time since it's in my parents garage.
   1. Issue persists after doing #4 below, and appeared after replacing the second brake pipe line and bleeding the brakes
2. Brake pedal goes to the floor - there is no brake fluid leak anywhere. In general very difficult to brake, I've only moved it from the garage to the drive way.
   1. Issue started after doing #2 repairs below, and appeared after replacing the second brake pipe line and bleeding the brakes
3. White smoke from the exhaust begins immediately at start up, and is constant - does not really smell like coolant.
   1. Issue persists after doing #3, and appeared after replacing the second brake pipe line and bleeding the brakes

Recent Repairs

1. Recently replaced the fuel feed line/return line (not the vent line) as it was leaking underneath the car. No gas leaks after replacement and car starts up right away - runs fine up until the low/high cycling idle.
2. Recently replaced two rear brake pipe lines as they were leaking brake fluid. After replacing, I bled the brakes all around the car until I saw no air bubbles/pockets. Did this with someone else and did it properly while making sure brake fluid in the reservoir was always full. The brake pedal went to the floor started after I replaced the second line.
3. Recently replaced the head gasket. Did this properly as well using advice from multiple forum threads on this site. Used Fel-Pro, took the head to a machine shop and had it pressure tested, cleaned, and resurfaced. I bought a feeler gauge/straight edge and could not get the .0015 gauge under the straight edge except for areas where there was obvious carbon build up. Machine shop said it was warped .004, assuming because I was able to get a .004 underneath the parts where the straight edge was over the carbon build up. Had it resurfaced anyways just in case. No cracks found with the pressure test. They also recommended a valve job which I agreed to since they mentioned cylinders 3/4 had fast leaks on the intakes, and I gave them valve stem (fel-pro) seals to replace as well.
   1. Block was not warped whatsoever, I took the feeler gauge/straight edge to it as well, could not get .0015 under the straight edge. I cleaned the head bolt holes from oil and torqued everything down in the correct sequence/order (and applied oil to the new bolt threads). I replaced the exhaust manifold gasket and intake manifold gasket (**** that green paper gasket that was installed, took 2-3 hours to take that off fml).
   2. Replaced other stuff like the camshaft seal, distributor o-ring, throttle body gasket, valve cover gasket
   3. Torqued everything down other bolts to specs if I was able to reach it
   4. Waited 2 hours after replacing everything before adding oil/coolant and starting her up
4. Cleaned the IACV with simple green first with q-tips and then sprayed it with a bunch of brake cleaner. I applied some PB blast to a q-tip and dabbed the valve. Still have the idle issue above.

I've read that the brake master cylinder gasket can go bad, which draws brake fluid into the intake manifold and then burns it (causing the white smoke?). Is there anyway to diagnose if this is truly the cause? I plan on replacing the IACV since it costs $25, but not sure if I should try bleeding the brakes again with the car on this time? Would there be any other reason the brakes go to the floor after bleeding and seeing no fluid leaks?

 

Block off the brake booster vacuum line and see if it runs better. Do not drive the car with the booster vacuum line plugged.

Your brake booster could be bad, or the check valve could be bad

 

Does this white smoke smell like antifreeze?

As far as possible leakage in the brake booster, it's what @chrysler kid said. Disconnect the hose from the booster to the manifold and look for brake fluid inside. Block the engine side and test run.

I think the Civic of this generation have an isolated design where a leaky master cylinder will run out between the cylinder and the booster and not let brake fluid enter the booster though.

If the master cylinder has gone completely dry, you need to "bench bleed" the MC then reconnect the lines and bleed the rest of the system. Bleeding should be done with the engine off. If you can't build any pressure after bleeding the master cylinder is likely bad.

 

So put some pliers to the brake booster vacuum line and the cycling idle stopped. Should I replace the whole brake master cylinder, or just the gasket/o-ring thing?

 

The seal between the master cylinder and the booster needs to be the right one and installed facing the right way (lips toward the outside). Leakage there can be spotted by a sucking sound when the engine is running.

If the booster is leaking somewhere other than there, the booster needs to be replaced. There are no field-serviceable parts other than the master cylinder shaft seal.

Brake fluid inside the booster will destroy internal parts and cause a sudden failure on the road, it needs to be replaced.

 

I don't remember any seal. On the hx model you have to remove the master cylinder and bend the lines a bit to get the alternator out. I dont remember having any sort of gasket or seal but it's been a couple years.

Go to the junkyard and get another brake booster. If you remove your old booster and its got brake fluid inside of it your brake master is bad too

 

Didn't have to bend any lines...

 

The y5 intake manifold and fuel rail are larger than the y7 or y8

 

I have a z7 with an EGR, did not have to move any brake lines. I'm damn sure we discussed this in the 'today' thread a while back and even took a pic.

 

I think I'll be doing a couple tests to see where the leak or hissing comes from. I'm fairly positive I remember hearing a hissing noise near the back of the engine. It looks like others in this forum have gotten away with just replacing the seal between the MC and brake booster.

Would anyone know if #4 and #5 are the same thing? I could potentially save a bunch of money if all I have to do is replace the seal...

 

I mean ive had 8 different hondas and the only ones that I had to remove the master cylinders for was the hx models. So I'm not sure what your point is.

 

I don't see a difference in the two and I'm not sure why you had to do what you did. Please attached image of both engine bays. The z7 isn't any different from the HX other than not having the vacuum inlet for the CC.

 

The y5 fuel rail is twice as thick and has a regulator with the metal return hose near the booster.

So I didnt feel like removing the fuel rail and lines so I unbolted the 2 bolts on the master cylinder

 

Thanks - going to order the seal since it costs $5. Will do some troubleshooting and will replace the seal first anyways to see if it fixes the problem most likely before committing to the brake booster.

 

if its smoking out of the tail pipe the master cylinder is leaking into the booster and you're sucking in brake fluid into the intake. Soo don't waste your time with a gasket

 

I misspoke before, I'll be replacing the seal. I'm going off this thread, and this looks to be an issue around a bunch of Civics. Apparently a deteriorated seal between the master cylinder/brake booster will cause brake fluid to suck into the intake and eventually cause white smoke (plus a cycling idle?). I've noticed a decent amount of brake fluid disappearing with no leak anywhere.

 

Not so good news. I started up the car after a week, and started with the radiator cap off to bleed the system a bit. I don't have a spill free funnel (it's coming tomorrow), but there was smoke coming from the open cap after a couple minutes. I capped it after it was boiling over quite a bit (should this happen?) and it continued to smoke around the area. There was no idling after a few minutes and I checked the exhaust and it looked fine with no smoke whatsoever (around 3-4 min in). This was totally opposite of what would happen previously, when it would cycle between a low and high idle within 5 minutes with some smoking coming out. I jumped in the car and pressed the brakes around 4 times and they went to the floor each time. After this it started cycling low/high (not sure if it was necessarily connected). After a minute or so I squeezed the brake booster vacuum line and after like 15 seconds it went to a different higher/rough idle (video below). Not sure if it is related either but it went into this idle after around two minutes of cycling between the low/high. I squeezed the vacuum line for around 30 seconds and nothing changed.

I ended up taking off the brake master cylinder and the seal that was between the booster/master cylinder looked to be in perfect condition. I replaced it anyways but I inspected it and there were no cracks or anything. Put everything back together and started her up, but same thing. I pulled off the vacuum line from the brake booster as I was replacing the seal to check for fluid inside the hose but didn't see anything. When I took the hose off I heard a bunch of pressure release. Is it worth checking the other end connected to the manifold for fluid? It's in a weird spot/angle so I held off and checked the other end.

I might be seeing more smoke come out of the exhaust now than before. Ran a compression check (used 1-2 tsp of oil for wet) and results were:

Dry (left side of head to right): 166 168 172 173
Wet (left side of head to right): 180 180 180 182

Sort of at a loss here. Check engine light came on and it's still P0505. I'm planning on doing the following tomorrow...

1. Start the engine and time when it begins to cycle between low/high, and time when it gets into the high/rough idle
   1. Will run a second test later with the brake booster vacuum line plugged from the onset to see if anything changes
   2. If it still cycles I can check the booster vacuum line connected to the intake
2. Bleed the coolant system once I get the spill free funnel
3. Potentially bleed the brakes, again, for like the 3rd time just to make sure I didn't miss anything... highly doubt this will change anything
4. Otherwise check for more smoke at the exhaust

Any suggestions for what I should troubleshoot? I might buy a leak down kit first and check for additional issues. May end up replacing the IACV just in case.

 

I answered your thread in the first post.

 

I had my non technical rents check it the first time. When I checked it today nothing happened, and if anything, it changed to a quicker/rougher idle.

 

Is that your car in the video? The squealing sound is not normal. Either it is running dry of power steering fluid or there is a bad bearing. Take all the outside belts off (A/C, P/S, alternator) and start the engine see if that noise is still there. If it is it's coming from the water pump or the timing belt tensioner and needs to be fixed immediately before the timing belt breaks.

Yes disconnect the booster hose and plug the engine side from the outset. You should have done this already. That will completely rule out the brake system as causing the engine problem

If the white smoke smells like antifreeze it is probably the head gasket (it could also be one of the parts on the intake that contains coolant, you can isolate those by disconnecting that networks of small hoses and replacing with one that loops around it). If there is a lot of bubbling or stuff blowing out of the radiator immediately after you start it cold with the cap off, head gasket.

 

Yep it's the car in question... was a hand me down from an uncle, and it's had bare minimum work done on it. Sat around for two years apparently in the Chicago area, so bunch of rust. So did two tests:

First
Blocked off the brake booster on the intake side and started the car on a cold start. Car ran normally for six and a half minutes (no low/high cycling idle) before going into the fast/rough idle as shown in the video. It's around 35-40 where I am, so sounds like it started idling once it reached operating temp. Smoke was coming from the exhaust, I would categorize it as sweet smelling. Smoke got heavier at operating temperature. I hear the squeaking around the timing belt as well, fairly odd. The timing belt looks new, the other belts all look old.

Second
Around 30 min later, I left the brake booster hose as is and started the car. Ran normally for three minutes before it started cycling between a low/high idle. Around thirty seconds later it started idling fast and I saw more smoke coming out of the exhaust. Going to link of video of this, actually caught it at the end where it just finished cycling low/high and went straight to the high. The exhaust sounds like its dropping a beat.


Also just checked, with the brake booster hose plugged in normally - anytime I depress the brake pedal, the idle increases. It doesn't increase when I press it down, just when I release it. The smoke around the radiator/cap was just coolant on the outside burning off, it eventually went away. Saw some white creamy liquid under the oil cap. Signs are pointing towards a coolant leak? On the bright side the radiator fan works, finally saw it come on. I am thinking I have a bad brake booster, I botched the head gasket job somehow, and now I have a squeaky pulley.

Thoughts?

You Tube

 

Bump. I'm thinking of replacing the brake booster with a remanufactured one, and if there's still an exhaust leak, then maybe replace the head gasket again.

I opened the radiator cap this afternoon after it was fully cold and the coolant looked as if none burned off. It was practically where I left it after bleeding it off. I mean potentially 1-2 oz could have been missing, but I left the car on for a total of about 30-40 min yday with smoke blowing out. Never got hot and gauge always at normal op temperature. I would imagine more coolant would've burnt than that... thoughts?