Help identifying noise in engine bay - Video added
Hi there. Just joined the forum, there's some really terrific info on here, such a great resource. I've done searching around to try and solve my problem, but so far I haven't found a match for the symptoms I'm experiencing.
Some background info, my girlfriend bought a nice little automatic '98 ae101 (changeover year) corolla the other day. It's in good condition with regular servicing and has been taken care of, however the old owners were by no mean "car people".
I'm hearing what seems to be an abnormal sound coming from under the bonnet. It is a type of "hiss" noise, not a deep clunk or creak. Most people who have heard it say it sounds like air, but i'm still open to other possibilities.
Now my first instinct was to check for a leaky vacuum hose or air filter assembly etc. No luck so far, but I'll give it all another check anyway.
I've done some testing trying to replicate the noise and have posted my findings below:
The car drives perfectly. Starts easily first go, revs and accelerates smoothly. No hesitation or backfiring or noticeable power loss etc.
Noise is dependant on engine revs. The car can be in neutral and still produce the noise.
Noise is louder under harder acceleration. It'll be quiet under idle, then louden quickly under load.
I've noticed the over all loudness of the noise will drop noticeably after a few minutes of driving. Seems worse just after start up.
What else do you guys think I should I look at?
The belts look pretty new, can't see any fluid leaks in the engine bay.
My girlfriend doesn't mind the noise at all, but it drives me crazy not knowing what it is, and it's definitely not normal.
Welcome to the forums! I experienced a similar problem when I installed a replacement motor into my Corolla a couple of years ago. It turned out that my intake manifold gasket was slightly worn which was causing a small air leak (the leak only became apparent after the swap as everything had been unbolted and then reinstalled, which would have caused the already weak gasket to deteriorate).
It would faintly hiss on idle and when accelerating, but apart from that there were no other side effects. It annoyed the hell out of me so I ended up taking it to a Toyota dealership to get their opinion and they said that it could have been the power steering pump. I was rather confident that it wasn't the PS pump causing the problem, so I removed the intake manifold and replaced the gasket with a brand new one. The problem disappeared after that and it hasn't hissed since. The problem that you're experiencing may be unrelated, but it's worth checking out if you've exhausted all other options. Good luck!
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Hi mate, thank for the welcome and thanks for your help.
what you describe looks to tick a lot of boxes for my issue so I think we could be on the right track. Thanks!
What I've done is upload a video of the noise, it helps explain things a lot better. Do you think it confirms your theory or could it be something else?
I also noticed a decent sized crack in the exhaust manifold which needs to now be replaced. Will do the cat at the same time also I think. This wasn't causing the hiss noise but it does have a noise of it's own.
I'm amazed that the car still runs perfectly smooth. I thought with these couple of leaks it'd be noticeable when driving. Maybe just the fuel economy is affected. I don't know.
No worries . I was actually going to suggest that you check the exhaust manifold next, but the noise from that would be a lot deeper (like a tractor) which you can also hear in your video. The exhaust manifold is very prone to cracking through the middle like in the photo you took. Mine cracked in the exact same place, and ended up cracking all the way around. Almost every other Corolla exhaust manifold I've seen has cracked like that too. They seem to have remedied the problem in the later Levin models.
The best thing to do would be to replace it with an eBay header. There's a guy on eBay Australia who is selling one for an AE92 Corolla, but it can also fit the AE101/AE102 model. However, his price is rather expensive, so it would actually work out to be a lot cheaper if you got one from eBay America. Even when you add on the postage to Australia, it still comes out cheaper than the guy selling them on eBay.com.au. The ones from the US are actually made especially for the AE101 and you have the choice of two different oxygen sensor holes depending on what your car has (the 2-bolt flange type or the screw-in type). This is guaranteed not to crack like the OEM exhaust manifold. If you get another OEM exhaust manifold from a wrecker then there's a very good chance that it will crack again, however if money is tight then it could be a temporary solution. Otherwise you can get your cracked exhaust manifold welded up, but again, this is only a temporary solution as it will start cracking through again.
You fuel mileage will definitely be suffering with the crack in the manifold like that. If you're going to replace the cat, I'd recommend doing it at the same time as installing the header (if you decide to purchase one). There's a great guide in this forum which explains the whole process - You can view it by clicking here.
As for the hissing noise, based on your video, it sounds like the exact same place that mine was hissing from. There's a vacuum hose on the bottom of the power steering pump, so I'd suggest checking to see if it's cracked/worn, but other than that it sounds like it could very well be the intake manifold gasket at fault.
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Hi mate, thanks for that.
I'll definitely check the hose underneath the power steering pump as I think I missed it. Would be terrific if that was the source of the issue. Nice and simple.
If not, how big a job is replacing the intake manifold gasket? I'd end up taking it to a mechanic. I know the gasket itself is relatively cheap, but do they normally charge an arm and a leg for this type of work?
Hi mate, thanks for that.
I'll definitely check the hose underneath the power steering pump as I think I missed it. Would be terrific if that was the source of the issue. Nice and simple.
If not, how big a job is replacing the intake manifold gasket? I'd end up taking it to a mechanic. I know the gasket itself is relatively cheap, but do they normally charge an arm and a leg for this type of work?
They all look pretty similar, just trying to find the cheapest one I guess?
Cheers
The intake manifold is quite difficult to get off, and there's a bit of work involved. If you went to a shop then you'd probably be looking at around an hours labour at the least. You can buy the gasket yourself from either Supercheap Auto or Repco (I got mine from Supercheap).
As for the exhaust manifold, yep that's exactly the kind you need to go for. You must first check to see which type oxygen sensor you have though. Simply look at the side of your exhaust manifold and you'll either see two rods poking out with nuts on the ends, or you'll see nothing. If you see the rods, then you have the flange type (same as the link you posted above) but if you don't see the rods then you'll have the screw-in type, which is also available on eBay, although not quite as common. It's also worth mentioning that the 1.8L header also fits on the 1.6L, except it sits slightly lower down. All of the 1.8L header options that I've seen have had the 2-bolt flange type oxygen sensor mount however, so if yours is a screw-in type then you'll need to stick to a 1.6L header.
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The intake manifold is quite difficult to get off, and there's a bit of work involved. If you went to a shop then you'd probably be looking at around an hours labour at the least. You can buy the gasket yourself from either Supercheap Auto or Repco (I got mine from Supercheap).
As for the exhaust manifold, yep that's exactly the kind you need to go for. You must first check to see which type oxygen sensor you have though. Simply look at the side of your exhaust manifold and you'll either see two rods poking out with nuts on the ends, or you'll see nothing. If you see the rods, then you have the flange type (same as the link you posted above) but if you don't see the rods then you'll have the screw-in type, which is also available on eBay, although not quite as common. It's also worth mentioning that the 1.8L header also fits on the 1.6L, except it sits slightly lower down. All of the 1.8L header options that I've seen have had the 2-bolt flange type oxygen sensor mount however, so if yours is a screw-in type then you'll need to stick to a 1.6L header.
Champion, thanks for all the info. It's a big help.
It looks as though mine is the 2 bolt flange type. I took a photo of it anyway, just in case someone else wanted to use it for reference some time.
The exhaust place down the road quoted me $300 for a reconditioned unit Off to eBay I go!
Quote:
Originally Posted by BoyYota
Don't forget you can use a hose to help you find the exact location of the sound, like a stethoscope.
Gotta love Army mechanics.
Oh yeah, heard about this. Will give it a go when I get some time. Theres a still a chance it could be a vacuum hose I missed. I'm still new to corollas.
Yep, definitely the 2-bolt flange type . Thanks for the clear photo by the way, that should come in handy if I ever have to explain it to someone in future. I'd recommend going for the 1.6L header as the 1.8L header hangs about 3/4" lower. It'll still fit, but it could scrape on speed bumps etc. I just had a look around on eBay US for you and this is the cheapest one I could find:
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Help identifying noise in engine bay - Video added
1993 Toyota Corolla
. I was actually going to suggest that you check the exhaust manifold next, but the noise from that would be a lot deeper (like a tractor) which you can also hear in your video. The exhaust manifold is very prone to cracking through the middle like in the photo you took. Mine cracked in the exact same place, and ended up cracking all the way around. Almost every other Corolla exhaust manifold I've seen has cracked like that too. They seem to have remedied the problem in the later Levin models.
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