Well I finally took the MR2 on a club run. It was a 400km round trip for me to Newcastle, and the car went great, and I thought everything was fixed. No overheating, temps were very stable even though it was a really hot day (and I have no aircon). I think I recall it averaging high 70s mid 80s, with a peak of 91. It was mostly highway klms though, with 2 hours in traffic at the end.

Once I returned and had parked it, I came back an hour later to find a small puddle of coolant under the car, which I worked out came from the overflow. I then drove home later that night carefully, with no issues. The next morning, I opened the radiator cap and found this, which looks like oil in my cooling system. I definitely have no coolant in my oil, as I had the sump off a couple weeks prior.
 


So now I am back to thinking I either have a blown head gasket or a cracked block, weeks before MTC. At this stage I am thinking of doing the following:
1. Compression test
2. Retighten ARP head studs
3. Another long drive
4. Compression test
5. Look for oil in radiator cap filler neck again. But without flushing the whole cooling system how can I distinguish between new and old?

I've been doing a little research on retightening ARP head studs and found this:

http://www.toymods.org.au...studs-how-to-re-torque

Has anybody else tried this? What process did they follow? I'm a little concerned about completely removing each stud nut, and also whether I wlll be able to get to the stud at the end of the intake camshaft (without removing camshaft) they refer to. Looks like the torques should be 65ftlbs.

Besides making my cooling system less efficient what will a little oil in my coolant system do at the track? I have also read this would eventually mean I will get coolant in my oil, at which point I will need to stop driving as coolant obviously doesn't lubricate bearing too well.

What other options do I have besides removing the engine, getting the block magnafluxed, replacing head gasket, and putting engine back together at this stage?

I would definitely try re-Torquing the app headstuds. They may not have been checked after the engine was originally assembled with them.

I would just keep driving the car for every trip you need to make so the problem eventually becomes obvious.

Mrskylighter
I would definitely try re-Torquing the app headstuds. They may not have been checked after the engine was originally assembled with them.

I would just keep driving the car for every trip you need to make so the problem eventually becomes obvious.

I agree. Don't panic yet.
Keep driving it and continue to check the look of the oil and the coolant.
You may find that the puddle underneath the car could just be from too much coolant in the overflow bottle.
I did this once in my Commodore (filled the bottle too much) and when my wife drove it the parked, it overflowed onto the ground. She wasn't able to contact me, so she called the NRMA and they towed it home! There was nothing wrong with it.
Let us know how you go.
 
FYI I used to have a lot of cooling system issues and they went away after I bought the oversized Mishimoto radiator.
https://www.mishimoto.com/mishimoto-toyota-mr2-90-x-line-radiator.html
Seeing how you have no thermostat, you may want to block the engine bypass pipes to ensure that you have maximum coolant flow through the engine. I can show you exactly what I have done on my car at MR2WPC.
All of mine are blocked/disconnected except for the pipes that go to/from the turbo.
 
For others reading this that have a thermostat - this is not recommended unless you drill 6 x 2mm holes in the thermostat, otherwise you will find that the thermostat will not open early enough due to no hot coolant flowing to the back of the thermostat to tell it to open.

There is some good discussion about the cooling bypass pipes here - https://www.mr2australia.com/mr2play/FindPost/60243

I noticed that the diagrams had broken links. Sorry.
This one should help. I found it with Google though edited it.
I have an external oil cooler so have blocked the stock one. I have shown which ones are blocked in the diagram using a red circle. The one that isn't blocked is green.
Basically - the only one that passes coolant is the line from the coolant outlet near the distributor to the turbo, and then to the back of the water pump.

 

Thanks Guys.
 
The puddle under the car is quite possibly be overfilling of the overflow bottle as I was using a wrong meaurement on the pickup tube (It wasn't much coolant). I will be pulling the top off the engine and retorqing the head in next couple days. I'm just hoping I can undo the intake cam and tilt it to get to the hard to get to head stud, without having to take off the timing belt and tensioner. Anyone know what camshaft should be torqued to after reinstall?
 
I'm not going to have time to flush the whole system so won't know whether the oil in coolant is pre-existing or after the head stud retighten. Do you really remove the whole stud, to relube and tighten further into the block? Wouldn't this release previous pressure applied to the head gasket, and potentially end up with less pressure on the head gasket, even though stud bolt torque is correct?
 
Blocking the engine bypass pipes sounds like an option as I also have an external oil cooler. Got me wondering how pipes are currently setup. I will take a look at yours Admin at MR2WPC. I've also been considering putting a thermostat back in, as car can be a daily driver too.
 
 

I wouldn't pull the studs out. I would just re-torque them in the same order as stated in the factory manual. Apologies if you said it earlier in the thread, though do you have the standard bolts, or ARP studs and nuts?
I would worry about causing undue stress on the metal of the head by removing bolts/studs one by one whilst the others are still fully torqued, and as you said, it may affect the seal of the head gasket and cause more problems.

You probably already know this but just in case. Make sure you loosen off each nut before you retorque it up again (instead of just tightening them as they are now). I think arp recommend torquing them up in three stages also (one pass at xx, then slightly tighter and then final go at xx)

That picture isn't too clear but you are certain that's oil? I would of expected it to emulsify if the oil and water was mixing.
 

Mrskylighter
You probably already know this but just in case. Make sure you loosen off each nut before you retorque it up again (instead of just tightening them as they are now). I think arp recommend torquing them up in three stages also (one pass at xx, then slightly tighter and then final go at xx)

Wait what? surely you can't be suggesting the OP actually loosens all the nuts and re-torques from scratch?  The OP has done over 400kms on that headgasket to merely undo the nuts and re-torque would IMO be a terrible idea given the situation who knows what lies between the sealing faces of the gasket and it could only get worse if you loosen it, not to mention the gasket has already been compressed (unless its a re-usable MLS gasket).
 
Not sure what ARP recommends for their torque sequence but if the final setting is a plain torque wrench setting with no additional angle for example 85N.m I would just check each of the studs at that setting, if it's an angle as well say 45N.m plus 90 degrees and you are going to loosen it I would be taking the head off personally.
 

Make sure to only do one stud at a time. Put a mark on the bolt/nut and head, back it off then retorque it and see if the marks line back up or is pulled a little tighter. Then move onto the next one

I warm the engine first then drain the coolant before doing this