Coolant leak at back of engine block, 2001 Ti

[TomForrest]

Howdy fellow Pathfinder owners,

 

As the title states I'm loosing coolant after long drives (2+ hours), I haven't seen any leaks whilst in the city, though apparently this could just be down to evaporation and 'pooling'. I only bought the old girl 3 weeks ago, and have kept my eye on the water and oil levels, it was only since heading out of town today that I noticed a drop, and a large one at that, she's always smelt a bit burny but I wasn't too concerned as temperatures were constant and there were no leaks. No worse than other cars I've owned that were fine.

 

She blows a small bit of white smoke on colder mornings, but all fine once up to temperature. Though today after a long freeway drive the engine was still very hot 2 hours after parking up which was worrying.

 

The problem is I'm meant to be heading across the country on a long trip, and can't afford to wait around for a week in some back water town while it gets fixed. From reading on here it looks like it might be worst case scenario and it's something that's a huge PITA/costly to fix, what's the best way of diagnosing the cause?

 

I'm really stuck here as I need a working vehicle, but don't want to cause irreparable damage by driving it with an unknown leak. Any advice on what it might be would be amazing, cheers.

[Slartibartfast]

I'm not familiar with your motor, so I'm not much help beyond the obvious. Hopefully it's something simple. A friend of mine had a ripped hose on his van that leaked slowly enough that everything would be just fine for a while, then the coolant level would drop far enough to cut circulation and the temp would shoot up. We limped it through the whole road trip by adding coolant regularly and he found the ripped hose long after we arrived home. It was hidden away behind other stuff and only seemed to leak when the van was up to temperature.

 

It could also be a head gasket issue. See if bubbles come out of the radiator if you start it with the cap off. Check the oil, see if it's got coolant whipped into it. I've seen a test where the guy put a drop of oil on some tin foil and heated it with a lighter--if the oil has water in it, it'll sizzle and pop as it turns to steam. If you've got or can borrow the tools, a compression and/or leakdown test might help narrow things down as well.

 

In the meantime, keep an eye on the temperature gauge and fluid levels.

[TomForrest]

Thank you for your reply. Sorry my reply is a bit long winded but I just want to cover everything to try and narrow this down.

 

I took it to a mechanic today, they couldn't see any sign of a leak at the back of the engine, suggested using a bandaid tablet to block any small leaks. Did as they suggested, heading out of town and 15km down the road it starts over heating, it had never done this before.

 

I immediately stopped driving and pulled over, it had started leaking s lot of coolant from the reservoir, I found a small crack on top of the plastic tank, magic a new leak!

 

I nursed it back to the mechanic when it was cool enough, they did a pressure test and found nothing, they also initially thought the fan may not be on its last legs but after a test they were happy it was still biting. We gave the radiator a clean out as it was a bit blocked up with leaves etc and he thought this was the problem. He said I would be fine to drive with a crack in the coolant reservoir (yeah skeptical about this) and sent me on my way.

 

I headed off again and all seemed fine till I hit some hills, nothing major and no serious inclines, the car started over heating again, it would drop back down after the first 2-3 extended hills but after about 30 minutes it just stuck at 9:45 on the dial so I pulled over, it's worth mentioning it normally runs at 8:30-8:45. And here I am wondering what I can do next! It's not spewing out coolant anymore but I really don't want to cook my engine. Any thoughts? I know an older car will struggle up a hill but after the 2 days I've had I'm not taking any chances.

 

Edit: just a quick addition from my email reply (figured I'd put it all here in case others can help) I've checked the oil and all good no 'mayonnaise' or foamyness.

 

Regards

Tom Forrest

[Slartibartfast]

A cracked expansion tank would explain a little coolant loss, but unless your motor is designed differently from motors I've worked on, that tank should be an overflow only--it shouldn't see very much coolant going in or out, and even then, only when the motor's hot. Coolant pushing its way out a crack--in the top--is very odd. I have heard of bad head gaskets pushing coolant into overflow bottles (exhaust gas displacing coolant), and there's a chemical test for this that looks for hydrocarbons in the coolant. Before you do that, though, check your radiator cap. If that's not sealing right (I replaced one in a friend's Yota where the rubber was half gone) it could be letting the coolant out when it's not supposed to.

 

But, again, I haven't worked on these. For all I know, that tank could be a pressurized part of the system that the tablet has marginally re-sealed. I think Chevy used that on some rigs. Hopefully your mechanic would've spotted that, though.

 

Cleaning the rad is not a bad call and it sounds like it helped. Any loss of coolant now that the rad is clean?

[TomForrest]

Sorry I should have been clear the crack (that is now a 10 cent hole, brittle stuff) is on top of the actual reservoir part of this plastic tank, not on the 'spout' to refill it, so it's around the same level as the max marker. My understanding is when the engine gets to operating temperature it pushes coolant into the reservoir due to a pressure increase. If I fill it to the max mark it will loose a fair amount on a short drive but then settles down to a much smaller loss, whether this is bubbling in the tank I don't know. The next time it starts to over heat I will pop the bonnet quickly before killing it to see if there is any 'bubbling' in the tank. Also very strange that the original leak at the back vanished to be followed by a much bigger problem?

 

I really hope it's not a head gasket, I've checked for all the other signs and nothing. Oil is clean, engine has been running fine before the last couple of days (first real test it's had), a small amount of white vapour on start from cold but that's gone in a minute or so, and none when warmed up. The water shows no signs of oil mixing, I will definetly follow your advice and get a test to see if there is any mixing, it could just be a micro crack if there's now major signs but some symptoms?

 

Unfortunately I'm a good 200km from the next town that might be able to help me, and in hilly conditions too! I'll make sure to post an update on whatever happens just so it's here as a reference.

 

Cheers for advice I'll get the test done as soon as a reach a large enough town, along with having a really good look at the radiator cap (which I imagine I would hear hissing when the engine is over heating).

 

Regards

Tom Forrest