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Just joined this forum, so here goes with my first post....
I have a 97' 4rnr with 250,000miles, recently I'm having a brief 10 second cold start misfire after which it runs fine. I am also losing a good cup full of coolant daily from the reservoir with no visible leaks! The heater sometimes blows hot then will just blow warm or cold then next day blow hot again! possibly due to an air pocket being caused by the leak, I have burped the system at least 10 times in recent months. This usually cures the heater issues and I'm thinking when it blows cool it's because the coolant levels are down and I'm getting air being sucked in from a leak somewhere that I cannot see, causing an air bubble usually in the heater core as the out hose doesn't get very hot..
The vehicle does not overheat. There is a very small creamy mixture just under the oil fill cap and also 2 very small streaks of the same stuff on the dipstick but non in the oil. Condensation in the winter maybe ??The coolant appears clean also. The plugs were all normal colors, not wet, just whitish when checked last few days.
Could it be that I have a small pin hole coolant leak in the HG, and overnight the coolant leaks into a cylinder causing the misfire in the morning until it burns off, usually in about 10 seconds. The 4rnr has plenty of power and no other drivability/running issues.
There is no visible white smoke from the exhaust, just the normal steam when cold -15c/-20c here in Canada !
So do these symptoms point to a head gasket problem ?
If the misfire is that consistent pull the plug and check them right after turning it over without starting it, or try pulling three plugs at a time and have someone turn it over well you watch. These 4runners usually leak from the rear heater lines first, under the little Aluminum guard by the T-case, thermostat housing due to corrosion on the mating surface, water pump housing mating surface or water pump, and lower rad hose. It is normal to see white under the oil cap. When my HG went from knocking off the lower rad hose offroading and run dry, you could smell the rad fluid in the exhaust and every now and then when you start it, it would hydrolock and you would have to crank it over by hand to force the fluid out of the cylinder to start it, needless to say I pulled that motor for a donor, easier than doing HG.
Exhaust having a sweet smell is a good sign of coolant entering the combustion chamber., You'll want to check it cold at first start up and again after it's reached operating temperature.
There shouldn't be a water oil mix on the stick, the cap, or the PCV system. Condensation build up is only going to show up if you're repeatedly doing very short trips and not letting the engine reach operating temperature.
Thanks for the insights guys, both saying opposing things though re- the white stuff under the oil cap ! I did read on this forum that every Toyota some guy had had all showed the white gunk under the oil cap and no HG problems. It's the 4th winter for this 4rnr since I have owned it and the first time for the white gunk to appear. I have smelt the exhaust and it's definitely not sweet at all.
I saw today there is a slight wettness from the bottom rad hose, but no drips on the floor. I tightened that hose clip up real good. The bottom of the rad on the engine side is also slightly wet.
Something else I noticed today after getting home, There was a 2 second interval "pop" "pop" sound which turned out to be air popping into the reservoir. The reservoir was still full from yesterday, however the rad needed topping up quite a bit. Why had the reservoir not filled the rad back up ? isn't that what they do ? Could I have a bad radiator cap ? I did hear a slight hissing from the cap too. Really hoping it isn't the HG.
Last edited by Aviator Mel; 02-07-2017 at 11:47 AM.
Confirmation, radiator cap gasket. Wouldn't hurt to clean off the fill tube there but doesn't help much once the gasket drys out. Go OEM cap it's worth the extra money unless you own a coolant factory *grin
However don't discount the head gasket isn't hissing also. Last one I replaced you could hear hissing, very obvious once the sparkplug was removed. I was going to suggest pulling the plugs and listening before but neglected to do so.
As for the conflict of info, a little bit of milkyness you might expect but just a slight haze and not in both places. The "streaks" on the dip stick sound pretty ominous to me. You can't just assume the oils good by draining it into a pan, in my experience you'll want to drop the oil pan and have a proper look to make sure it's not sticking to walls and such..
For example I pulled my whole engine and replaced it over an oil slick in the radiator, that oil s still stuck to the inside of the old radiator and didn't drain out. Oil slick turned out to have been barfed out of the rear seat heater from when the former owner blew an engine and never flushed it. Not a bad turn out honestly since the cam was shot on the one I pulled out but the HG was intact and now I have a spare!
Sludge just tends to stick like that. And that's just one example.
Not familiar 4rnr engine, but if it has an oil cooler, check to ensure it is not leaking coolant into the engine. Easy start is a radiator pressure test. I got the loaner kit from O'Reily's. The kit also has the adapters to let you test the radiator cap. Of course, does not tell you what is leaking, just that it is leaking.
Another easy, reliable, cheap test is the block combustion test. Again, some auto parts stores have loaners and you just have to purchase the test fluid ($8.00 per bottle and you only need about 1/4 of the bottle to run the test). Essentially you are checking the radiator head space for combustion gases. Can also be done with a multi gas meter if you have access to one. Principal is the pressure from the cylinders is substantially greater than the 15lbs in the radiator, thereby, forcing exhaust gases into the radiator. The tester lets you draw air from the head space through the test fluid which reacts with the exhaust gas and turns it from blue to yellow or yellow/green. I found this test to be very accurate. As a tip if you run this test, ensure the tester seats well against the radiator neck, otherwise you will draw in air from the overfill tube and get a false negative result.
Are you sure it's the rad cap gasket that's the culprit here? I really hope so. Would that explain the slow bubbling into the reservoir tank when engine running ? What about the misfire at cold start ups ? This doesn't happen everytime however !
Are you sure it's the rad cap gasket that's the culprit here? I really hope so. Would that explain the slow bubbling into the reservoir tank when engine running ? What about the misfire at cold start ups ? This doesn't happen everytime however !
radiator not refiling from the expansion tank is a bad radiator cap, usually a flattened dry gasket sometimes a weak spring.
I can't say for sure the bubbles are just air expanding or exhaust gasses, but the test kit (co2 or whatever fluid the test kit is) mentioned above will.
Well the rad cap looks like the original from 1997! reckon it's due. I have been losing coolant actually for over a year just not as much as just recently, so could be that the rad cap has been to blame. Picking one up tomorrow then and see it that cures it.
Sounds like you have a leak, if you have a leak the system will draw air, when the system heats up it pushes rad fluid to reservoir, when it cools it draws the fluid out of the reservoir if the system is sealed, if there is a leak close to the rad or main hoses, rad cap, rasorvior line, it will draw air instead as it is easier. Have you ever changed the rad in this truck (replacement is every 200,000km or 10-15 years. T-state housing, water pump or lower rad hose leaks it will show up on the rad or lower rad hose. And again condensation under the oil cap is normal, streaks on the dip stick isn't though. And most don't change motors over a rad fluid leak unless its a HG. Your losing a lot of fluid and your exhaust doesn't smell like rad fluid and you keep getting air in the system so your losing rad fluid from a leak and drawing air in, the rad can leak at the end tanks and evaporate making it hard to find the leak but you would smell it after a good drive.
I am hoping it's exactly that Malcolm99. I am inclined to believe it is drawing in air. I have burped the system at least 3 times since Jan began. After each time I get, not hot, but quite warm air in the cabin, but within a day or two cools right off, due to more air getting in the system.
I do not know if the rad has been replaced, I am guessing it has, I got this 4rnr at 352,000km's, because it doesn't look too shabby at all, even looking inside the cap opening it looks reasonably clean. I have driven 50,000km's since I bought it. There are no visible signs of a real leak from it, no dried coolant anywhere at the corners. No idea about the Tstat either.
I just replaced the bottom rad hose 2 weeks ago and it does get a bit wet still around the clamp and I think it's spraying coolant into the fan cover shroud as it's wet on the bottom of it, but not dripping. I nipped it up tight yesterday again. That could be where the air leak is!!
The heater valve is new and there are no visible leaks anywhere else. The water pump was replaced when I got this truck, no leaks there.
Some days, yes, I do get a good coolant smell, so there's an external leak somewhere.
Getting a new rad cap tomorrow, so with this and a re-tightened bottom rad hose that might do the trick.
So am I correct thinking that if the rad cap is bad and together with the lower rad hose letting air in, that is why I am getting a slow bubble into the reservoir tank ? Rather than exhaust gases from a blown HG ?
Still doesn't explain the cold start brief misfire, however this isn't everyday ! That could be the cold temps and a bad injector !
Sounds like your on the right track. Make sure that Rad has been replaced, they are known to fail by mixing the Rad fluid with the Auto Transmission fluid costing you a tranny, Google "strawberry milkshake toyota", mine was perfectly fine at 200,000km and I tossed it in the scrap and replaced it with a over the counter parts store rad. if your rad smells like steamy rad fluid it may be leaking from the end tanks., for $200 and a bit of rad fluid I'd swap that rad as a reg maintenance item if you have an Auto tranny
I fitted an external tranny cooler in the summer to avoid any possible milk shake so I'm good on that point. Yup, a new rad I think is a good move next. I also fitted a new Napa rad cap today which is working in as much as the bubbles have stopped in the reservoir tank also, the cap wasn't hissing like yesterday with the old cap, so there's one fix done! Possibly too much coolant in the system also as some had come out and wet the front of the motor and alternator area, looks like it came from the cap ! I know some are going to say I should have got OEM now!
Taking it into the shop tmrw for a pressure test too for blown HG or not.
Well an update, I put on a new rad cap which must be working 100%, the pressure is so good in the hoses now that the new found pressure has blown out somewhere and covered the front of the lower part of the motor in coolant. The black fan shroud is all wet too, but where is it coming from ? Did the rad take a dump ? It's a new bottom hose, Water pump was new 3 years ago.
Don't know the age of the rad, could be it's time for a new one.
Blizzard outside tonight and no garage, so will have to wait for a sunnier warmer day, could be a while. Might have to park her up for a while until I can investigate more. This would happen in the middle of winter eh !
Luckily I have my Scooby Doo Outback.
New rad and T-stat fitted,no leaks or drips and no blown HG either. All is good again, running like a champ. Old rad was toast. Long past needing to be replaced.
Yeah, the radiator was all wet under the top of the fan cover under the top hose area when I took it off. It wasn't very nice looking inside either, well over due to be replaced. I got a Koyo from The Wrench Monkeys. The T-stat was actually replaced in 2012 and was an OEM one. I actually put in a new one from NAPA, a Motorad T-stat which could have been a mistake by what I am now reading about them. The original Toyota one works still so I perhaps should put that one back ! Just found a guy locally who does frame welding too. He has 3 Toyota trucks and says he can fix my frame !!! Not that I'm in a bad way for 20 years of our winters in Canada, just need some patches to pass the Inspection.
Yes the OEM T-stat is ideal, Carquest was able to get me the OEM T-stat but it was almost as expensive as at the dealer, my original T-stat looked great at 200,000km, make sure it is clocked correctly when installed. I wouldn't bother patching the frame unless you can do it without noticing the patch as its really hard to paint the inside of the patch on a boxed in frame and it will rust out in no time in Canada, look for another replacement 4Runnner and inspect the lowest 4 corners of the frame before buying, there are still mint low Km 4R's out there for a decent price in Grandma's garage.
I'm still having coolant loss issues here ! Can anyone say where it's going ? There's a new radiator, a new radiator cap, a new T-stat, new hoses and clips, no visible drips anywhere now from any hoses ! I filled the overflow tank to the Full mark yesterday and topped off the radiator Today, after driving less than 100km's the coolant in the radiator needed filling back to the top with approx a pint, the overflow tank level never moved ! It did not get pulled back into the radiator. I have no oil in the coolant and I have no coolant in the oil. Yesterday I had a clean tailpipe, meaning no steam after warming up. Today I did have a little amount of steam even after an hour of driving, the weather was the same both days, +10c ish.
When I switch off the engine I can hear an air bubble escaping into the overflow tank once every 3 seconds only and not for very long. I don't think that's normal ! Is this a sure sign of a bad HG ?
Now if there is a high-pressure leak happening would it lose up to half a pint to a pint of coolant in under 100km's of driving?
Is it possible I have a crack in the Head allowing the coolant to evaporate off or burn off in the engine which is giving me the steam in the exhaust even after an hour driving ?
No, I have not done a cooling system leak test yet, I might have to.
I have some block sealer which will be a last resort.
02-06-2017, 02:59 PM
