EJ25 overheating saga

[falco]

Everyone likes a good story, right? Here goes...

I bought a cheap 1997 Grand Wagon about six months ago, to use while I worked on my other Legacy. I didn't really care what condition it was in, it was cheap, road legal, and drove well. That went fine, so when I finished the other Legacy, I kept using the Grand Wagon for towing and other fairly hard work. I noticed that sometimes on the motorway, the engine temperature dropped to the point that it was below cold. Checked the thermostat - it had the centre hacked out of it. Obviously someone had done that for a reason, but figured I'd replace it and find out. Did that, and the car still ran fine, but maintained temperature on the motorway as it should. Checked for head gasket leakage - nothing obvious, no water bubbles. So I kept towing multi-tonne trailers around with it, and then, on a long-distance trip while stuck in traffic, the temperature gauge started creeping up. I found that if I brought the idle up a bit, it would stay cool, so I did that while stopped, and made sure revs didn't drop too low while driving, and it made it back fine, despite towing a massive load. Checked the water again, and found that it was losing water, and there were now bubbles in the radiator. So, pulled the engine, replaced pretty much everything (head gaskets, water pump, and mountains of other things... no more oil leaks). Great, water bubbles gone. But, WTF, the temperature is still getting too high. When idling, it comes up to temp fine, sits there for a while, then starts creeping into the overheating region. But, the radiator fans weren't coming on. The radiator also didn't seem nearly as hot as it should be. But none of that makes any sense.

So here's the questions:

- Anyone have any details on the exact wiring config on a BG9 Grand Wagon, that runs the fan(s)? Looks like the ECU is supposed to trip relays, which run the fans, but I can't find good diagrams on that, and everything on the car is in Japanese.

- Why wouldn't the radiator be getting hot (it's warm on the driver's side, cool on the passenger side)? The thermostat and water pump are new, the radiator's been professionally flushed and checked, was filled with the bleed cap open.

I could just toss the thing away, but I've spent a lot of time and effort on the engine, so I'd like to resolve the situation. The car also has a reco transmission and steering rack, and drives amazingly well. It deserves to be saved, I reckon...

[SpeedySub]

Blocked radiator? Maybe will repairing something blocked it?

Edit: just reread and saw it had been flushed. But maybe something has been dislodged after?

[Rosssub]

Should be a sticker on the underside of the engine bay fuse box lid showing which are the fan relays, main fan relay and Sub/AC fan relay. Assuming the 97 Grand Wagon would have the test mode connectors under the dash, the fans should cycle on and off in test mode.

http://www.scoobypedia.co.uk/index.php/Knowledge/ReadingECUCodes

Does the heater blow as hot as it always has? Could be a blocked heater core if not and a bypass might help:

https://www.dirtyolbc.co.nz/community/topic/94-how-to-bypass-the-heater-core-to-stop-the-engine-overheating/

[lachlan]

What do these have as far as an air bleed for the drivers side rad end tank . It will always create an air lock there . Dies it have a hose from there back to a top tank ? If so make sure this entire hose is hot . If top rad hose is hot a d the lil hose isnt it maybe vlocked or jus full of air . or some models have a tap there . Failing that jus undo the hose clamp and wiggle it back to near the end of the spogot on the rad and bend it downwards so it creates a tiny leak at the top . Make sure water comes out your leak .

[falco]

Thanks for the suggestions!

 Rosssub']Should be a sticker on the underside of the engine bay fuse box lid showing which are the fan relays, main fan relay and Sub/AC fan relay.

It does, but I'd like to get a detailed idea of the config, i.e. where fuses sit, how cabling is routed, if there's anything else in the line that could have failed, etc. I don't think I'll be able to find anything, so I'll just go with what I've got.

Edit - The engine bay fuse lid layout details a lot of A/C-related relays, but nothing that's obviously related to the main fan. Maybe the descriptions are bad. There are 4 A/C relays, and a 'sub fan' fuse, that's all.

The A/C fan does come on, but that doesn't seem to help with the engine cooling situation.

Assuming the 97 Grand Wagon would have the test mode connectors under the dash, the fans should cycle on and off in test mode.

Yep, have gone through that. Currently it reports no errors, but definitely no fan cycling going on. Should it definitely be doing that? An interesting sign, if so.

Edit - Rechecked this just now. It goes into diagnostic mode fine, but there's no relay clicking I can hear, and neither of the fans cycle on and off.

Does the heater blow as hot as it always has? Could be a blocked heater core if not and a bypass might help:

Good question! Never tried that. I'll give it a go.

Blocked radiator? Maybe will repairing something blocked it? Edit: just reread and saw it had been flushed. But maybe something has been dislodged after?

It's possible, but the radiator wasn't blocked originally, and the flush etc. didn't show much up either, apparently.

[quote name='lachlan said:

What do these have as far as an air bleed for the drivers side rad end tank . It will always create an air lock there . Dies it have a hose from there back to a top tank ? If so make sure this entire hose is hot . If top rad hose is hot a d the lil hose isnt it maybe vlocked or jus full of air . or some models have a tap there . Failing that jus undo the hose clamp and wiggle it back to near the end of the spogot on the rad and bend it downwards so it creates a tiny leak at the top . Make sure water comes out your leak .

Yeah, I was pretty careful with bleeding, these don't have a separate top tank like the turbos etc. have. It's just a simple radiator and a couple of main hoses. But one thing - I did it on a nose-down slope. Not a very steep one, but maybe it was enough to screw it up and introduce a big air bubble someplace there shouldn't have been one. I'll turn the car around and redo it, with the nose facing up. That should remove any possibility of blockages.

Edited January 17, 2016 by falco

[falco]

Well, I think it's all fixed. Turns out that the four relays are really badly labelled. I think:

1: Main fan

2: AC (secondary) fan high speed

3: Who knows?

4: Compressor

And strangely, the main AC fan relay is under the dash, behind the ECU.

Two faults were resolved. Firstly, the ECU decided to turn on the secondary fan when the engine got a bit warm. I'm pretty certain it wasn't doing this before, but no idea why - it just did it this time. Plus, the main fan connector was making bad contact. Gave it a clean up and plugged it back in, and the ECU now controls it fine, so temperature at idle is now stable. Hopefully a win - I'll get it a WOF and drive it around for a bit, see how it goes.

[Marky]

That explains the fans not coming on, but doesn't explain the other stuff you talk about (radiator not heating up etc)

I would still be querying blocked heater core like Ross said, for what it's worth. Very common (like, just google EJ25 overheating) and also very simple to work around (just 2x tee junctions joining the heater lines at the back). They should both feel hot hot once car is at temp

[falco]

 Marky said:

That explains the fans not coming on, but doesn't explain the other stuff you talk about (radiator not heating up etc)

I would still be querying blocked heater core like Ross said, for what it's worth. Very common (like, just google EJ25 overheating) and also very simple to work around (just 2x tee junctions joining the heater lines at the back). They should both feel hot hot once car is at temp

Yeah, I did check that - the heater worked fine, so I didn't worry greatly about it.

My best guess at why the radiator wasn't getting as hot as I'd expect was just that water flow at idle might be pretty low, so the engine's pretty sensitive to incoming water temperature. There definitely are still some mysteries - why the ECU wasn't turning on the secondary fan, and why the radiator wasn't getting very hot when the engine temperature was reading high. When I had the overheating problem initially (this is before any work was done, including the radiator flush), the radiator was very very hot. The driver's side tank was so hot that even a quick touch was painful. But, that was after overheating while driving, a bit of a different situation.

I think all I can do is exercise it a bit, and see what happens. If anyone thinks of anything else I can check, I'll give it a go.

[natho]

seen similar problems on another forum - apparently the small rubber hoses to the thermostat housing were kinked. might be worth double checking those?