Blowing Noise - where to look?

Post by **nigelbi** » 21 Jul 2007 10:39 pm

On a 340 1.7 1988 vintage. I've got a blowing noise in the engine compartment area. It's from the manifold side I think but I don't know where.I've checked exhaust manifold to exhaust by trying to feel blowing and wrapped it in cloth but noise is still there. So I'm assuming it's not that. Tried looking underneath manifolds with a mirror but couldn't see anything. Felt around for blowing but only succeeded in getting burnt hands. I'm not sure whether its a manifold blow or from one of the many breather pipes the engine seems to have which perhaps has split.

Any common points of failure I should check before a full strip down to try and find the blow - which I appreciate I might need to do anyway to fix.

Thanks

Nigel

Post by **redline** » 21 Jul 2007 11:37 pm

funnily enough (or not ) my redline cracked its exhaust manifold ,
I didnt even know until the young lady that bought it from me got the car home . the car had been off the road about 5 months between my last using it and her buying it as I had bought my calibra I dont know where it cracked but there may be a thread om here somewhere about it

edit , found the thread

http://www.volvo300mania.com/forum-uk/v ... ght=#49243

Nigel , whats the reg number of your redline mate

Post by **Ronnie** » 22 Jul 2007 08:21 am

Get a friend to put their hand over the end of your exhaust pipe with the engine running - if the noise gets a lot louder it's definitely something to do with your exhaust! Could be a knackered manifold as Mick said, or manifold gasket blowing or maybe even the joint between the manifold and down pipe. Good luck.

Post by **pettaw** » 22 Jul 2007 09:30 am

You're doing the right things, just not at the right time......Wait for the engine to cool down and do it again.

Start the car up first thing in the morning after its stone cold and then put the choke in so the revs are minimal, that saves the manifold and downpipe getting too hot for you to touch without getting your hands burnt

Suspect parts are the downpipe area and the manifold joints to the downpipe and the head. Cracked manifolds are extremely rare on non-turbo cars, because the engine just doesn't generate enough heat.

Don't trust garages to give a correct diagnosis, when most of them see an old car they think "get rid of as soon as possible." We never did find out what was the problem with that Redline car with the exhaust problem (convinced it wasn't a cracked manifold), because the girl sold the car with all faults. Unfortunately that was the end of it, because last I heard the car has been scrapped.

Post by **classicswede** » 22 Jul 2007 10:47 am

I Have cracked a 1.7 manifold. That was running with the 2ltr lump and the manifold would glow red hot at times (melted 3 down pipes with it). Fitting the 1.8 single point injection exhaust manifold solved the problem.

I agree with Andy on this one. Asunming that it does sound like an exhaust blow its most likely to be the down pipe joint or the gasket between the head and manifold.

I have had a 1.7 that sounded like it was blowing after much investigationa dn not being able to find any sign of a blow I eventualy dicoved a damaged valve by compression test.

Post by **nigelbi** » 22 Jul 2007 12:45 pm

Thanks for all advice - I'll have another look at what is going on and have a go at doing the checks advised - registration for reference is
F335 KHJ

Cheers

Nigel

Post by **pettaw** » 22 Jul 2007 02:01 pm

classicswede wrote:I Have cracked a 1.7 manifold. That was running with the 2ltr lump and the manifold would glow red hot at times (melted 3 down pipes with it). Fitting the 1.8 single point injection exhaust manifold solved the problem.

I agree with Andy on this one. Asunming that it does sound like an exhaust blow its most likely to be the down pipe joint or the gasket between the head and manifold.

I have had a 1.7 that sounded like it was blowing after much investigationa dn not being able to find any sign of a blow I eventualy dicoved a damaged valve by compression test.

OK I stand corrected. Bear in mind though that you're running LPG, a bit famous for generating more exhaust heat than normal, especially if its not in perfect tune

Post by **foggyjames** » 22 Jul 2007 04:44 pm

Not to mention the amount of gas being thrown down the rather undersized exhaust. You can see where the points of restriction are on a thin-wall 'header', as they glow hottest - and it's usually the 'pinch points' which glow first.

cheers

James

Post by MJ » 22 Jul 2007 05:55 pm

A trick I've heard before is to put a few drops of oil into the air intake of the carb. This creates a fair bit of smoke which you should see coming out of the leaking pipe at the location of the leak.

You'd have to take out the air filter to put the oil in though, and I wouldn't recommend running the engine without a filter, but it's just an idea...

Post by **foggyjames** » 22 Jul 2007 06:48 pm

You'll be fine running without an air filter for a few minutes, especially just at idle. Just don't drive at full chat through the Sahara

cheers

James

Post by MJ » 22 Jul 2007 07:19 pm

I know it should be fine, I just wouldn't want Nigel destroying his engine following my advice

Post by **Chris_C** » 23 Jul 2007 10:16 am

Or, instead of oil, chuck proper red redex down it. That creates loads of pink smoke, and cleans your carb at the same time

Post by **morgan105** » 25 Jul 2007 11:23 am

Providing it's not windy, not much chance of that with the weather we've had lately

, holding a piece of tissue paper or very thin paper around (not on!) suspected areas usually can find where a leak is as it's very sensitive to any breeze put at it. When it starts flapping around you have found a leak.

Works for me every time.

morgan105

Post by **classicswede** » 25 Jul 2007 10:36 pm

pettaw wrote:
OK I stand corrected. Bear in mind though that you're running LPG, a bit famous for generating more exhaust heat than normal, especially if its not in perfect tune

The slight extra heat from the LPG was the small part of the problem. The manifold was fine when I had the 1.7 but the 2ltr was just too much for the manifold. On petrol I dare say you would just about get away with it.

Post by **huskyracer** » 25 Jul 2007 11:16 pm

Classic swede

You melted a down pipe ???????? you seriously need to check exhaust gas temps, dont get above 1k c, or bad things happen, if things get that hot you are at a minimum sacrificing a good chunk of power somewere at a minimum and at worst runnning a very real risk of it dropping the head off an exhaust valve.
You can get high temp thermocouples from RS components, If you need one I may have a couple spare someware, but seriously mate thats not good, and I dont think its an exhaust restriction thing imo, on some badly matched turbo setups, we see over 20 psi back pressure in the manifold, and even the cheesy chinese ones dont melt, ok they crack alot but dont ever melt!!

Sorry for the thread hijack, carry on......