‘88 Mitsubishi Galant Cold Start Noises

[Mitsu_Joe]

Hey,

as it starts getting colder where I live, I started to encounter a strange gurgling noise when cold starting my car. It seems to come from the top of the engine.
As I stated, its a quite muted and sounds almost like gurgling, maybe that's just normal valve train noise. Its my first winter with that car so I can't really tell.
It used to also occur sometimes in summer but just for a couple of seconds. Also it's just apparent at idle. While I give it some gas it quiets down immediately and runs extremely smooth and quiet all across the rev range.

https://youtu.be/wswX4lmduj0

I am talking bout that gurgling/clapping noise. Temperature wasn't even that low, like 50 degrees F. I'm currently using Castrol GTX 10W-40. After 1-2 minutes the noise goes away and the engine runs very well when cold, as well as warmed up. And it can't really be from oil starvation, the engine delivers oil into the head as far as I've seen and why should it deliver oil into the head at 70 deg. F but not do that for minutes at 50? The change in viscosity isnt that great overall.
I hope you can follow my thoughts, if it was a general oil starvation problem it should occur on any startup, at least for a short period of time.

But this must be oil-related as I also get the same noise if I start the car in summer, but using too thin oil. The owners manual states that 5w-oils arent to be used in temperatures higher than 70 deg. F, if you ignore the warning, you get besaid sound. Especially on warm starts.

The engine is an oldschool l4 1,8l carbureted gasoline sohc unit with rocker arms (without rollers or anything fancy), manual valve adjustment (no hydraulic lifters!). The engine design itself originated in the late 60s.
That's why I can't really believe that this old engine could be that picky about oil, maybe its just a normal sound with the antique valve system and I'm exaggerating things. According to the owners manual it can even be driven with sae30 in temperatures not lower than 30 degr. fahrenheit...I am safe to use my 10W oil at temperatures as deep as -20 deg. F according to the owners manual, so I dont see how it could get problems feeding oil into the head at 50 F...

Besides that, she's a keeper... Just 90k miles, clean internals, doesnt consume any oil, great compression and overall runs very well.

 

[mk378]

Sounds more like an exhaust leak than any sort of mechanical engine noise. Regardless, have you checked / adjusted the valve clearance? Some valve noise is normal on such engines, especially when it is cold. The parts expand as it warms up, tightening the clearance and reducing noise.

 

[Mitsu_Joe]

Valves have just been checked and adjusted.

I checked it today; unscrewed the oil filler cap and started her up. Even immediately after start up enough oil reaches the head and oil pressure seems great, the noise remains.
Strangely its more hearable from the drivers seat than at the engine bay itself.
Could also be an exhaust leak, especially as that car has quite a free flowing exhaust from factory because of the lack of bigger mufflers or big catalytic converters.
It isn't rusted out or anything, though. My current thesis is that there‘s just play in the valvetrain and that the noise is that apparent because of the free flowing exhaust and no real soundproofing of the engine.

So I‘ll just take it as given, especially as those engines were never famous for their smooth idling, but for their sturdiness and bulletproof construction.

 

[StevieC]

Having worked on a lot of Mitsu's in the past I can tell you they are quite fussy on oil flow. Try using an OEM filter and see if it makes any difference. A friend of mine in Kuwait just had issues with his Mitsu and it was the oil filter causing it.

 

[Snagglefoot]

Check your exhaust manifolds and make sure there is a nut every where there should be. If the stud breaks, the nut will be gone and the manifold may loosen enough to leak.

 

[dave1251]

It sounds like a exhaust leak. If it isn't mechanical you could try Castrol magatec.

 

[Mitsu_Joe]

I used to think that this was something oil related, but now I'm kinda on your side with the exhaust leak. If the noise was really coming from the valvetrain, it'd be in much faster frequency...
Furthermore this engine is rated safe to use SAE30 at 30 Fahrenheit, so why should it have a problem with 10W-oil at 50 F?
I checked the oilflow through the engine, seems to be good. Lots of oil in the head, oil pressure warning shuts off immediately after start-up, if you listen carefully you can actually hear a tiny bit of background sound coming from the valvetrain in the video, so this particular sound must be due to something else, namely something exhaust related...

Still leaves unexplained why besaid sound also occurs in summer with too thin oil... My only thought would be that due to the old engine construction there is a bit of play in the valvetrain which should be normal. Thin oil in summer (and in winter when clearances are bigger) doesnt manage to compensate this play inside the engine. Due to an exhaust leak this rough sound becomes more apparent than it should usually be. But maybe as I stated it's not even really a leak, the car is quite loud even from whats coming from the exhaust tip...

I really wondered how free flowing that cars exhaust was, first owner granny car, I doubt she modded the exhaust system.
But you get warm legs standing 50cm away from it as it expells warm air that far making that typical dull "whopwhopwhopwhop"-sound...

You can also feel the pressurized air pushing out from each single cylinder firing at the exhaust tip with your hand from like 20-30cm away from it, so maybe they riced it out from the factory already... But I kinda like that sound to be honest, it never seemt that out of the line for me when warm...

Here's some clips of warm idling, warm acceleration up to 3000 rpm in two gears and a pull to 5500 rpm in second gear...

https://youtu.be/-u-BgogYAzE

Actually sounds quite good for a 1.8l l4 that just pushes out 86hp...

I'll check for any leaks though in the coming days...