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Engine overheating & losing coolant

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08 Aug 2018 19:14 - 09 Aug 2018 08:18 #194921 by Mithrass
Hi guys,
I'm hoping one of you experts can help a strictly amateur mechanic to fix his Jimny.
I have a 2003 O2 convertible - for fun, off-road and for my son to use when he is home. It has the G13BB engine - 1298 SOHC. Recently it began to overheat and lose coolant. The radiator was full of mayonnaise. I immediately thought the cylinder head gasket had failed so, rushing in, I took it off. (A lot of cursing and improvising special tools, but ok for a guy who last took a car apart 30 years ago.)
Having finally got to the gasket, I could find no sign of leakage through it. I'm posting some pictures. All comments and advice are welcome.
This is the head as removed, with the gasket still in place. https://ibb.co/eVstT9
This is the head with the gasket off and turned over. https://ibb.co/dSNtT9
This is the top of the block with the head removed. https://ibb.co/nC4MgU
The only clue I could see was one of the cylinder head bolts was heavily coated with a carbon deposit. https://ibb.co/byTggU
Here's a closeup of the corner where the bolt came from. https://ibb.co/jofSMU
Does this mean anything to anyone? All advice gratefully received.

The images are attached in order. I can't find a way to make them appear in the text.
Attachments:
Last edit: 09 Aug 2018 08:18 by Mithrass. Reason: Correct an image URL and add attachments

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08 Aug 2018 22:06 #194925 by S200KYS
Difficult to see your photos from that post...

Here you go, for others to see -



This is the head as removed, with the gasket still in place.

This is the head with the gasket off and turned over.(same link as above photo?)



This is the top of the block with the head removed.



The only clue I could see was one of the cylinder head bolts was heavily coated with a carbon deposit.



Here's a closeup of the corner where the bolt came from.

Is It Sunday Yet? :)
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09 Aug 2018 07:51 #194932 by Mithrass
Thanks for that - it's very helpful to see the images. I was expecting live links inserted in the text but it didn't work. I see I copied the wrong URL into one of the images too.
I'll see if I can edit the original post.

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09 Aug 2018 09:20 #194938 by Lambert
Looking on the picture without the head gasket there do appear to be a couple of unsealed section on the right hand cylinder. Did you get the compression tested before you removed the head?

It's not a Jimny. It's my Jimny

Mooo said Ermintrude (black)
Boing said Zebedee (blue)
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11 Aug 2018 21:00 #195037 by kirkynut
Well you've taken the head off now so get it skimmed just enough to ensure it's flat and put it back on with a new gasket and head bolts.

Then you'll know if it was the issue for sure.

Kirkynut

The underdog often starts the fight, and occasionally the upper dog deserves to win - Edgar Watson Howe.

My Jimny Thread Here: www.bigjimny.com/index.php/forum?view=topic&catid=8&
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12 Aug 2018 17:11 #195052 by mickt
When you took the bolts off did they all seem to be the same torque?
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19 Aug 2018 15:32 #195264 by Mithrass
Many thanks to everyone who responded. I've been following up those suggestions and probing around in between domestic commitments.
To answer the specifics...
Lambert: I see two places that look like combustion gas was escaping, and looking at the gasket I can persuade myself there is a corresponding mark on it. That would explain the carbon deposit on the bolt, but it doesn't show any path for oil to escape into the water jacket. Maybe it's a general indication that the head was not tight at that corner. There is no visible defect after cleaning the head surface.
I didn't think about a compression test. Too late now.
Kirkynut: The head and the block both test flat within tolerance (.1mm) and I'm fighting shy of taking out all the valves and refitting them, so I will refit the head with a new gasket and see what happens.
Mickt: Yep, all the bolts felt the same. They were very tight - tighter than I would expect for a 10mm head, even with 12-point drive. I had to use the torque wrench in reverse to free them. Haven't looked at the specified tightening torque yet.

More generally, looking around, it seems cheaper to buy a whole Jimny same age as mine than have the engine replaced. The risk is I end up with two identical cars,both with clapped engines.

Thanks for the help everyone.

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28 Aug 2018 15:54 #195496 by Mithrass
For the record, I put the engine back together with new gaskets. I had three screws and one nut left over. To my astonishment it started first time and ran nicely.
After a while it became clear that the thermostat wasn't working.

Looks like serious overheating. I still don't know why.
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28 Aug 2018 18:13 #195503 by mickt
Well if that was the original thermostat then that's probably caused the overheating! .Did you torque the bolts to the specified figure using a torque wrench?
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28 Aug 2018 21:58 #195509 by Mithrass
The thermostat looks to be permanently open, so I would expect the engine to be overcooled. That was the symptom I saw - it just never got the temperature gauge off zero. The damage to the thermostat could be an effect of overheating, but that must be a really strong wax capsule to buckle the valve like that.
Yes I put it all together by the book - even half tightening the head bolts then releasing them before taking them to full torque. Just like it says in the manual.

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29 Aug 2018 14:35 - 29 Aug 2018 14:39 #195530 by Scimike
Have a feel of the radiator to make sure its not blocked. Start engine from cold and wait for the thermostat to open, ok not with your thermostat ^^^, but you need a replacement anyway.
When it opens the radiator should heat up evenly across the complete matrix. Cold spots in the direction of flow through the radiator indicate a blockage. Not sure which way the flow is, but assume its hot top to cold bottom. So any difference in temperature between the left and right side must be a blocked channel. Heat should flow evenly down the radiator when the thermostat opens.

Sorry if this has already been suggested.
Last edit: 29 Aug 2018 14:39 by Scimike.
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29 Aug 2018 15:22 #195532 by Mithrass
Thanks Scimike, I'll try that - when I get a new thermostat. Apparently the one I ordered from BJ is the wrong rating for this engine. I could just put it in and try it anyway.
I am more concerned that there may be a blockage inside the engine itself. It got really gooey when it was spitting oil into the water. I've flushed it out but there are parallel channels where one might be blocked. I dread to think what would happen if one side of the engine was cooled and the other not.
The water pump seems ok - it pumps out water when I disconnect the radiator top hose.

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