Ideas please - Slow overheating issue - 2JZGTE

[The Real Roadrunner]

if it still sucks coolant back in that would indicate the system is sealed which would generally rule out a HG prob, but without seeing it i wouldnt know where to start looking.

[wa5]

You cant mount the thermostat in reverse as it fouls on the pipe mount, but you make a very good point that i will try and explain. The issue with the thermostat staying shut is that the cold coolant passes through the thermostat opening causing it to shut, then the coolant being bypassed around the engine tries to open it again, only to be put off by the cold coolant causing it to shut again. Its a cruel circle, but since ive drilled a few holes into the outside of the thermostat, it allows the coolant to pass through even when the thermostat is shut, which eventually leads to all the coolant getting hot enough for the thermostat to open. The only problem with this set-up is that it takes a while for the engine to warm up. Hope that makes sense.

Cheers
Ben

Engine cooling really is not my forte (if I do indeed have a skill it is probably making smart arse coments ) but I am a little puzzled. .. when the thermostat opens it lets HOT water out of the engie. to the "top" of the radiator this water circulates to the "bottom" and then back into the motor. where it "collects heat from the block and head before passing the thermostat agian.....

So why is the thermostat getting a big enough dose of cold water to shut it as soon as it opens? when that water should have picked up enough heat in the block to keep the thermostat open? where is the cold water coming from?

are you running the factory thermostat in the factory location? IE is there some sort of wierd after market thermostat (possibly linked to this bypass setup) set up in a non factory location?

[wilbo666]

Engine cooling really is not my forte (if I do indeed have a skill it is probably making smart arse coments ) but I am a little puzzled. .. when the thermostat opens it lets HOT water out of the engie. to the "top" of the radiator this water circulates to the "bottom" and then back into the motor. where it "collects heat from the block and head before passing the thermostat agian.....

So why is the thermostat getting a big enough dose of cold water to shut it as soon as it opens? when that water should have picked up enough heat in the block to keep the thermostat open? where is the cold water coming from?

are you running the factory thermostat in the factory location? IE is there some sort of wierd after market thermostat (possibly linked to this bypass setup) set up in a non factory location?

Factory JZ thermostat location is the after the lower radiator hose

Cheers
Wilbo

[sbyder]

Went for a good cruise last night.

Raced a mates series 6 Rx7 (on a private road of course) and then immediately travelled home for 10 minutes. Straight after the race coolant temp was 92°. Drove all the way home, stopped at traffic lights, coolant got up to 96° then once i started driving again it went back down to 90°.

Pulled up in the driveway to open the garage door and after 2 minutes coolant temp was up to 98°.

Very strange! So basically, the radiator and engine fan will keep it cool as long as im doing either certain rpm at idle, or im moving fast enough. If i go for a "thrash" it wont necessarily cause the engine to over heat.

This would normally indicate that i dont have enough flow to the radiator, but I find this strange as ive had the same setup for 6 months before and it never got close to 98° even in traffic on a 35° day.

Cant find someone to do a dye test locally. They all ran out of dye. Still looking though.

Ben

PS - thanks everyone for your updates and ideas. Hopefully it will lead me to the problem soon.

[Kyosho]

It sounds like your cooling fans aren't moving enough air through the radiator at idle, OR the pump isn't moving enough water at idle.

[Kyosho]

Did you remove the shroud from the radiator and leave it off?

[rms]

This would normally indicate that i dont have enough flow to the radiator, but I find this strange as ive had the same setup for 6 months before and it never got close to 98° even in traffic on a 35° day.

Exactly.
It is circulating too much water through the bypass system and not enough through the radiator.

Something has changed in your thermostat/bypass.

If you want to prove the point - remove the t/stat and block the bypass
Don't leave it like that though !

[sbyder]

good point. I might revert the heater bypass system back, as it really didnt do much anyway.

Ive gotta find a good pic of how the 2J cooling system flows, because I know that once the thermostat opens fully, it blocks the bypass system off. So if i remove the thermostat altogether, i dont know whether it will cause more dramas.

Thanks!

Ben

[MR 1JZ]

2J and 1J cooling system are the same yes?

you cant remove the thermostat all together as your cooling system wont work and most of the coolant will flow through the bypass rather than the actual cooling system

[sbyder]

yeah, pretty much the same system, and I thought so.

By the way, nothing changed in the system initially. It started to overheat, then i started to swap bits out.

[rms]

So if i remove the thermostat altogether, i dont know whether it will cause more dramas.

Ben

You MUST block the bypass if you remove the thermostat !!!
If it is internal then you can not block it easily.

Your problem is in the thermostat/bypass area.

[sbyder]

well i hope so. I have a endoscope tool thingy and ive had a good look up inside the waterpump and the blades are all good, and i cant see any blockages.

[wilbo666]

Posted by JP (Kudos to him)



Cheers
Wilbo

[sbyder]

thankyou VERY much for that. *Right click save*

But guess who has a BHG?


Thats right I do! And here was i thinking 2J were tuff...


At least I know whats wrong with it now so I can work out how to attack it.
Sell it as is (of course letting the buyer know and dropping price)

OR

Fix it myself and sell it fixed.

OR

Have someone else fix it and be outta pocket for the next 10 years...

decisions decisions..


So thanks everyone for your input! Dye test confirms I have a blown head gasket. Still no water in oil or oil in water, but must be big enough for the dye test to come back positive within 1 minute.

Anyone have the part numbers for the top engine gasket kit?

Cheers
Ben

[MR 1JZ]

fuck man that sucks

maybe now its tiem for a HKS gakset, ARP Studs and a T88-38GK?