Bizarre French engineering...

[wuvvum]

I spent a happy Sunday afternoon working on the Saviem. First of all I had to get the indicators working, which was fun - when the indicators were switched on my multimeter showed that the bulb was getting 10.5 volts, but it wasn't lighting at all. It was earthed fine as it lit straight up when I ran a wire directly from the battery live terminal to the bulb. Eventually I gave up trying to work out what the problem was and just wired in a completely separate indicator circuit using a cheap 3-position switch and a flasher unit I found in my box of bits. It all works fine, although there's now a lot of unsightly wires running through the cab.

 

Anyway, once I'd done that the next job was to investigate the exhaust blow. So I removed the engine cover, and this is what I found.

 

 

The exhaust is blowing from the gasket between the inlet manifold and the exhaust manifold. You can see the split in the picture. My question though is this: why in the name of all that is shite is there a fugging gasket between the inlet and exhaust manifolds? I can understand the manifolds being bolted together for strength, but that isn't what's happening here. The exhaust manifold is actually closed off by the inlet manifold. What the hell is the point in that? Maybe the two manifolds are joined together in one happy muddle of inlet and exhaust gases? Maybe there's only one valve per cylinder? Answers on a postcard please.

 

Anyway, this now means that to cure the exhaust blow I have to remove the carb (a downdraught Solex, reasonably easy to get at), then unbolt both manifolds from the head, and then unbolt the 40-year-old allen bolts that hold the two manifolds together at the join where the gasket is. I wonder how many allen keys I'm going to snap trying to get those undone? Bloody French motors...

[retrogeezer]

Squirt some no nails or gripfill type grab adhesive round it, works a treat.Lasted about 6 months on my Mondeo so I re-did it and still o.k. Big hole where the pipe goes into the silencer too, but a tube of cheapo grab adhesive is only £1.50 so it's cheap for a few months of quiet exhaust.

[j-j]

Oh come on dudes! this is easy! It's a pre heating arrangement to help keep the manifold hot with lots of cold air rushing in through the carb shortly after start up. The exhaustage will bash out a lot of wasted heat that can otherwise be used for heating the inlet manifold. It's an odd set up though as it would often be done with one of the cooling pipes from the cylinder head going through a 'jacket' around the inlet manifold but hey My GSA had a heat riser from the 2 exhausts that joined the manifold and formed a jacket round it, the CX has the normal boring system with a pipe of hot water out of the cylinder head and through the manifold jacket but it's doing the same thing.I guess it also serves to strengthen it too - genius French engineering I'd say!

[wuvvum]

It's a pre heating arrangement to help keep the manifold hot with lots of cold air rushing in through the carb shortly after start up. The exhaustage will bash out a lot of wasted heat that can otherwise be used for heating the inlet manifold. It's an odd set up though as it would often be done with one of the cooling pipes from the cylinder head going through a 'jacket' around the inlet manifold but hey

That's what a mate of mine suggested, but like you say I'd only ever seen it done with a water pipe before now. And surely just bolting the inlet and exhaust manifolds together would help heat the incoming air? The exhaust manifold heats up pretty quick that close to the engine, and with the inlet sat straight above it surely you'd get enough heat to it without having to direct the exhaust gases onto it (and create another potential and awkward-to-repair weak spot in the exhaust system)? Just ask my Skoda Rapid, which has a similar non-crossflow layout but with a separate inlet manifold above the exhaust, and starts to suffer from fuel vaporisation after 15 minutes at 90mph because of the heat coming off the exhaust manifold.

[nigel bickle]

Its French -need I say more?

[uncle silvia]

My corolla is a bit like that and its Jap quality!!!! The bottom of my inlet manifold actually has fins which sit in the exhaust causing a warming effect!!

[j-j]

The bottom of my inlet manifold actually has fins which sit in the exhaust causing a warming effect!!

-cool, that's something else that appeals to me about old cars - the little variations in engineering solutions that varied quite a bit from country to country. The days of choice...