My engine has only done this twice, but two times too much. When I start the engine, it makes about four knocking sounds in 1-2 seconds. Like: ta-ta-ta-ta. It occurs when the engine is warm. As I said, it has only happened twice, but most recently today and it has me worried. The oil level is fine, ambient temperature is about 12C. Thanks for any help.
Need some help diagnosing 1.8T noise
- Thread starter Vince58234
- Start date
- Status
bump
- Joined
- Sep 28, 2002
- Messages
- 39,798
Normally I'd say that the filter was empty ..but that usually happens cold and not usually when the engine is hot. The ADBV usually holds somewhat and doesn't drain off that quickly. With no cold symptoms ..this is not a likely cause.
Did it happen when the oil hadn't been changed for a while?
My guess too would be the filter draining back. Is it in the top or bottom of the engine? Did it just start? (with this filter/oil) What filter brand?
The filter is located on the bottom of the engine. So wouldn't gravity prevent the oil from draining back? The filter is Mann. Thanks.
Oil was changed about 1K ago.
Oil was changed about 1K ago.
And this just started, it has only happened twice.
OK way out in left field and not to argue with the oil filter drainback theories, these are likely and possible. Could it be sparknock caused by a leaking fuel injector and the "light fractions" auto igniting at start up. One way of diagnosing it would be to thicken the oil as in STP if this has an effect then the oil drainback theories are supported, a different oil filter would be in order. If a load of premium gas reduces it then a leaking injector is supported. Good luck hope this is helpful. Rickey
Keep in mind this is a really sporadic occurence. I've started the engine warm a lot without this happening. Rickey, I like your leaking fuel injector theory. Does the frequency of this occurence support it? I am already using premium BTW. Would the temperatures get that high at startup? I'm also using colder plugs, than stock, so it's even less likely I suppose. hmm
Interminttent start up knock... pheew thats a tough one... for me at least. Is it a sharp or a dull sound? I realize its probably hard to remember from only two occurences. Fuel injectors can develop an intermittent leak. And if its a piece of trash in the injector it may pass and cause no more problems. Maybe a dose of fuel injector cleaner is in order. Techron ane Berrymans are my personal favorites. Good luck. Rickey.
I just ran an application of Berrymans in my last tank full. Maybe it dislodged something and it lodged in the injector. I'd say the sound was half way between sharp and dull. Thanks
What about the TB tensioner?
If the TB tensioner was bad wouldn't it be noticeable throughout the operating range of the engine? Plus I changed it 20K ago.
- Joined
- Sep 28, 2002
- Messages
- 39,798
I'd say if it was a timing chain tensioner that it could be the cause. Just clacking a bit until the oil pressure pushed it outboard. That's nothing unusual for such designed engines ..at least at a certain point in chain slack.
If the anti drainback valve isn't working correctly, oil can drain back into the sump. Check that the filter is tight first (I have seen this happen with a loose filter). Just change the filter. Filters get manufacturing defects.
It has a timing belt actually. I'll try changing the filter tomorrow. If it is the filter wouldn't I get a low oil pressure signal and a DTC(Diagnostic Trouble Code)? I checked for DTC's, no faults found.
I tried to reproduce the engine knocks under similiar conditions today, but they didn't occur.
I tried to reproduce the engine knocks under similiar conditions today, but they didn't occur.
I believe that the problem is the timing chain tensioner. The exhaust cam is driven by the timing belt. The intake cam is chain driven from the back of the exhust cam. The tensioner moves the chain "up" or "down" to advance or retard the intake timing. As long as the noise goes away within a couple of seconds at startup, and there is no leak of oil onto the back side of the engine. Then there is not much to worry about. Just put a new gasket under the tensioner next time you replace the timing belt. This will require removal of one or both cams, but only adds a couple of hours to the timing belt swap.
- Status
