Postby lighthammer » December 19th, 2012, 1:58 am
Had a recent problem with my cooling system.
Symptoms are as follows:
- while driving south for recent off-road rally, engine temp suddenly and without previous warning started to climb, so much that the AC suddenly became warm (no previous indication of malfunction)
- stopped and cooled down, saw that radiator water level was low and coolant was brown-coloured and smelled "scorched" (didn't smell like new coolant)
- after cooling off, replaced old coolant with 50:50 mixture of NP Radol coolant concentration : water that I bought from a nearby NP Quickserv
- drove home, checked for leaks/broken hoses/radiator defects/water pump problems/Clutch fan oil leak or free-play when engine off - NO PROBLEMS AT ALL.
Over the next couple of weeks, the overheating problem remained.... but in a slightly unusual way:
- at idle and slow-driving/traffic crawling, engine temp stayed absolutely normal, and AC was cold throughout the whole time
- but when driving at highway speeds, engine temp would start to climb again once I reached over 3000 RPM, but would cool down after I backed off the throttle.
- Eventually took out the thermostat and checked it in a pot of boiling water, was opening and closing properly at operating temps.
- drove without the thermostat for a couple weeks, still had the overheating problem... temperature climbs at 3000RPM or 110km/h or more on highway... but not at lower speeds
- still no signs of leaks, water levels and coolant levels were good, changed out the NP Radol and used Prestone coolant, clutch fan was working properly (supposed to have mild resistance when engine hot and turned off, free-play when engine warm means the clutch fluid is worn and needs replacing)
- took off the radiator cap when engine was cold and switched on, revved the engine and got a good flow of water coming spewing out of the cap... meaning the water pump was working properly.
- scrapped down the radiator and did a flush through the top-cap - the water coming out from the bottom outlet was clean and clear, hence I could assume no deposits inside (plus it was a sealed system and I always used bottled water to top it up, to avoid mineral deposits cuz my local water table is quite hard/full of calcium).
- washed out the radiator and condenser fins.... LOTS of mud in there from my offroading adventures (took about an hour of washing and half a container of purple blaster to get the water to run clean!)
So... i couldn't figure out what was the problem... until I read the article above and something clicked...... I WAS USING THE WRONG COOLANT.
The NP Radol and Prestone coolants probably weren't rated for the operating temps for diesel, or at least it was out of the operating range for my Navara's YD25ddti - I dunno, maybe I had mixed them wrong, or I put them in on the wrong proportions. I thought to myself that maybe the coolant was meant for gasoline engines, and not so much for the hotter operating temps of a diesel.
So I immediately went down to the nearest Motorist shop (since it's a nissan) and got some Original, genuine Nissan coolant that was rated for my Navara's engine - paid $425 for a large container (approx 1 1/2 gallons, can't remember the exact size). Simply poured the entire contents of the large bottle into the rad and coolant bottle, was exactly enough for fulling the radiator and bottle to exact limits!! (guy at motorist said no need to mix, just pour straight in).
Also bought a new thermostat for the YD25DDti engine (might as well change it, the nav was running at 72,000km on the Odo anyway).
Result - no more overheating! I even ran the engine at 4200rpm for approx 5 mins (stayed in 5th gear and gunned it all the way to 110km/h), put the ac on full blast - and nothing happened. Needle stayed put like it was painted onto the dash.
So here were some of my conclusions:
- use proper rated coolant for the correct application. A trusted and well-competent mechanic friend of mine said that coolants do differ in quality and you get what you pay for. $45 for a gallon of Prestone vs. $450 for a couple gallons of Nissan original coolant will definitely make a difference (plus something about pre-mixing in exact proportions, surfactants, minerals etc in the original coolant that the Nissan engineers intended, that 3rd party coolants could never match esp for specific vehicles).
- make sure you clean your cooling system at least once a year. A radiator flush at a reputable radiator-garage will benefit you greatly, as well as checking your thermostat every 50,000 - 60,000km. Try to use original parts for thermostats.
- my navara has 4" of lift, meaning it's a lot taller than stock navara's, plus it runs 305/60R18 mud terrain tyres - hence the engine has a lot more work to do, a lot more wind-resistance on the highway, etc. This translates into higher loads on the engine esp at high speed... which probably is why it only overheated at load/high speed and not at idle. The engine was working too hard for the 3rd party coolant to keep up with.
So folks.... that's the moral of my story. Hope you enjoyed reading it and if anyone learned anything from my experience, then I'm happy.
Keep on Truckin'!