2007 Renault Clio III ocassional overheating, poor fuel economy

Hello all,

My second time here, same car.

Car sporadically overheats, specially on traffic, with no A/C on.

It has had quite the repair history so far, will try to resume here:

- Had cam timing issues, found after quite a long investigation: www.scannerdanner.com/forum/post-your-re...ignal.html?start=130 . This was fixed setting cam timing properly. By this time, one of the cylinders was slightly low on compression (115psi vs. 125psi on the rest). Can't recall which one.
- After that, cylinder head presented rust issues, had it resurfaced at machine shop and refitted at a car's shop.
- Coolant radiator had leaks fixed and thermostat housing replaced due to cracks into it. No leaks present in the entire cooling circuit (it held pressure fine in the test).
- Refitted original coolant temp sensor. Shop suspected of the new one included in the thermostat housing (the replacement part comes closed, includes housing, thermostat and coolant temp sensor).
- I personally found the cooling fan resistor was broke. Replaced with an original one.
- Had several trips to the same shop, different issues according to them: 2 coil packs replaced, 1 fuel injector replaced.

During the entire history since the cylinder head job, I've been suspecting of cam timing issues. Which the shop denies completely. According to them, they triple checked, but I'm not so sure, since they've tripped with some probing questions I've made. They even said the owner checked it personally with some kind of "gun" he was lent. Sounds like BS to me.

One of the latest test they performed was a compression test. They measured one at 90psi max. They didn't show the rest of the cylinder's readings though.

MAP readings at idle have been out of the spec range ( < 410mb). Last reading was ~500mb at idle (warm engine). Gets worse with AC on.

And fuel economy is bad. Before all of these issues, got about 8.9km/L. Now I get 7.2km/L.

Not to mention loss of power when taking off (is that the term for when you come out from a full stop?) and/or above 3,000RPM.

Is bad timing a logical possibility? Or should I look at something else before? If you need any further info, please let me know.

Thanks for your help and patience.

Hey Albert! FYI, your thread still has the record for longest thread on these forums.



The overheating in traffic issue... When it's overheating, is the fan running? I ask because it's possible to have an intermittent control issue, or a fan motor with dead segments that can cause an inop fan intermittently.

One of the latest test they performed was a compression test. They measured one at 90psi max. They didn't show the rest of the cylinder's readings though.

MAP readings at idle have been out of the spec range ( < 410mb). Last reading was ~500mb at idle (warm engine). Gets worse with AC on.

And fuel economy is bad. Before all of these issues, got about 8.9km/L. Now I get 7.2km/L.

Not to mention loss of power when taking off (is that the term for when you come out from a full stop?) and/or above 3,000RPM.

Is bad timing a logical possibility? Or should I look at something else before? If you need any further info, please let me know.

Red flag. :blink: Does it misfire at idle? Because that's usually what happens with a cylinder that low on compression. I'd be very interested to know what the other cylinders produce.

Timing is definitely possible. But, if all the other cylinders show reasonable compression, then I'd suggest digging into the cylinder with 90 PSI. If they all show low, then dig deeper into the timing.

(Dang, I wonder if holding the longest thread in the forum is an honor of a shame!)

- Fan seems to be working properly. Since I changed the resistor, fan engages at exactly the specified temp ranges by the manufacturer. Before changing the resistor, low speed didn't engage, and when turning the engine off after a moderate drive, fan didn't engage either. Now it does both.

Actually, the sequence just before overheating (as per the temp gauge) goes roughly like this:
- Slight increase in engine vibration, like if the mixture went off about 2 minutes before overheating.
- Hi-speed fan audible from driver's seat. (It's only one fan with two different speeds). Stays on for ~3 minutes. From there, there's a 50% chance of temp needle going one mark above operating temp. It occurs specially on the first drive of the day. I used to think outside temp had something to do, but I now doubt that since outside temp has decreased considerably, and it still happens.
- It takes a while (about 2 minutes) for the needle to return to its operating temp mark. Most of the time it does, but when the AC is ON, it doesn't seems to go back to normal unless I turn the AC off.
- Scan data indicates slightly unstable RPM at idle. Like 690RPM +/- 40RPM. Hard to feel it by vibrations alone.

Thoughts?

I'll see if I can get a hold of the tool to check compression myself. Don't really want to go back to that shop.

Will report any new data I get.

Thank you guys!