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Spanish R4 1108 annoying Rattle

J

jon_r4

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21
Hello.

I have a Spanish R4 TL with 1108 cc engine, it has an annoying rattle which is more noticeable when the engine is hot and when you want to go at a constant velocity i.e at fourth at 80 km/h.

I have checked the ignition timing, and I have adjusted it to 14º static, and the dwell angle to 55%... anyway the rattle persist.

What do you think about this problem? could be carburettor related?

Thank you for your attention.

Jon
 
14 degrees static advance???!!! Are you sure? It should be 4 to 6 degrees (depending on engine version).
 
Hi Angel.

I am not sure... but I have two identical R4, one red and the other yellow. The red one works fine. I have measured its static advance... and was 14º... This is why I have tried with this advance.

Anyway, the change I have done in the advance has had no effect, the problem off the rattle persist.

I thought that 6º was for small engines...

Thank you for comments and happy new year.

Jon
 
I don't know what your rattle sounds like. Too much advance results in a tinkling sound while going up hill and destroys the engine. But I wouldn't call it a rattle. (it can also cause a repeated knocking when it's very bad but still not a rattle).

Is your exhaust hitting the inner wing under load? That's always a good cause of rattle noises in the Renault 4.
 
I am sorry because my English is getting a little bit rusty...

More than a sound, the problem is that the engine does not go smoothly when I try to go at a constant velocity... is as it hesitates. Is like it likes to go as faster as it can.

After looking for it... finally I have found a spanish R4 1.1 GTL user manual, and Angel, as you say the timing static advance should be 6º +-1º.

I wonder why the red one is at 14º... perhaps my timing light is not working properly or... Anyway I will change the vacuum advance unit (of the yellow one)... to see if the problem is solved. Constant velocity = little engine load = high vacuum on intake...

If the problem persist I will check the carburettor.

Thank you for your answers.
 
Do you disconnect the vacuum advance line between the carburettor and distributor when you check the ignition timing? Not doing that could lead to very misleading figures.

Sounds like a timing problem or another fault with the ignition. There's not much you can adjust on the carburettor that would affect high speed running.
 
Instead of using your timing lamp de-phaser, set it to 0 degrees and check that the mark on the flywheel aligns with the right mark on the clutch bellhousing window (when viewing it from the front). This means 6 degrees ignition advance, the other mark is TDC.
You must disconnect the vacuum advance unit when checking timing, and idle speed should be correct (700 rpm).


Of course there are a millon other rattle sources (especially on a R4!) other than engine pinking.
 
Hello.
After changing the advance to 6º the problem was still there so I have done an exhaustive verification of both ignitions... I have done 3 measurements. The first one the advance curve of each one without vacuum, the second one the advance curve with vacuum, and during both test I have connected a vacuum gauge to the vacuum manifold... So here I have the results.

GRAPH.png

Red line: Red R4 results (the good one)
Yellow line: Yellow R4 results (the problematic)

My own conclusions:
The centrifugal advance units works fine on both distributors.
The vacuum on the red R4 (the good one) is slightly bigger (lower pressure it means higher vacuum), but the total advance is smaller. So I guess that both vacuum units on the distributor are ok, but the spring of the yellow one is loosen and I have to check if there is some kind of limiter to avoid advances higher than 45º.

Are you agree with the interpretation of this results?

Later I will post some more pictures.

Jon
 
Last edited:
My respect, this is extensive research!

I do not have advance curves for the 1108 engine, but roughly they seem correct.
Renault did not give an added advance curve (centrifugal+vacuum simultaneously) as, for a given RPM, it can vary depending on engine load (=manifold vacuum). They gave one curve for centrifugal (degrees vs rpm) and one for vacuum (degrees vs mmHg)
Again, in no load conditions (=maximum manifold vaccum) total advance can reach 60 degrees...

Of course, the point is that since the rattle continues even with timing corrctly set, it must be not pinking-related. I cannot think anything...maybe timing chain?? but I have never met a timing chain that rattles at engine speed more than 1500 rpm...
 
Hi Angel.

This measurements were done with no load, so we can assume that the vacuum advance is at its maximum.

I have obtained the data of the maximum advance of the vacuum unit of their distributor (C52) and it is 15º. I have calculated the difference between both advance curves for each car, and for the red one (good) results are 13º max advance due to vacuum (a bit less than 15º), but it is near. On the other R4, the yellow one (the problematic) the difference is of 26 º, and here we have a big difference... so I guess that the assumption I made about a problem on the advance mechanism is gaining relevance... it seems like that the spring of the distributor has given away and that is why vacuum advance is bigger than what the engine needs, thus beginning on mid range, in conditions of no load it pinks a little (see the picture below, into the red box). I can go on 4th at 50 km/h perfectly without feeling anything from the engine (In this scenario the vacuum on intake manifold is low due to the low revolutions of the engine). On the opposite, If I pull the accelerator, then the vacuum on intake manifolds decreases (so the vacuum advance is reduced) and that is why I do not fell anything wrong either when I am accelerating (even going at 80 km/h or more).

distributor.png


I will try on Thursday to buy a new spring to see what happens. (Tomorrow here in Spain is holiday). Wish me luck, because sometimes is hard to find this small parts.

Finally, I would like to explain better the problem I have with this car,And I guess I explained it before, but to try to transmit the problem I have with this car better, I will say that more than a rattle (a sound) I am talking about a feeling, I feel like the engine fails, still, it can go on... I do not hear any sound but I can feel that the engine is not working smoothly, some kind of vibration is transmitted.

Excuse my rusty English and accept my most sincere apologies because this post is getting very large.

Best regards
 
Note that values on advance curve diagrams refer to distributor advance, you multiply with 2 to get what you see on the crankshaft with your timing light.
 
Thank you Angel.

I have taken in account this detail, for the C52 vacuum advance unit the distributor advance is 7,5º, on crankshaft 15º.

Tomorrow I hope I will finish with this problem.
 
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