Very High Pressure in Coolant System, Help Needed

Quick explanation as this has been going on for a while

I originally found a leak from one of the bulkhead hoses, repaired this thinking it was just an old hose

After bleeding the system I noticed the pressure seemed a lot higher than I thought it should be, I did some searching on here and Google

and was sort of questioning myself, thinking I was just over worried, due to all the Engine problems I have had since Whifbitz put it in

Maybe just an Airlock etc

Anyway moving onto the last couple of weeks and last few days, been in contact with Lee on and off during the whole thing and I have changed the thermostat and Lee sent me a replacement Rad Cap

I was still not happy with the pressure the system was holding and Lee suggested a sniff test next

I had one booked for tomorrow, but I went through all the main hoses tonight and then rebleed the coolant system, the car had been running for about 30 mins I guess and was at full temperture with Electric Fans cutting in and out and then bang, the coolant hose to the Turbo's (the one underneath) had a hole in it

The thing I really don't understand is how the pressure in the system can get so high, surely the Rad Cap should relieve the pressure, the pressure gets so high that I can not even squeeze the Rad Pipe

The overflow bottle doesn't seem to get much if any coolant going into it during warm up, it did draw a small amount in on cool down on the run upto temp before this one

I am really at a loss on the pressure side, even if the Head Gasket is going, surely the pressure should be forced through the Overflow, that is how the system is design or am just not understanding it correctly

Sorry for the long write up, but I am really stuck now and about to have to give up on the Dragonball, so this is the last ditch effort to work it out

Just to add, as I know someone will ask, the heater is blowing nice and hot

The system gets up to temp, thermostat seems to be working correctly, although it is surprising how long it takes to get all the coolant hot

The system has had 2 Caps and 2 Thermostats and no change

Sniff test it first.

What's the temperature gauge doing?

it is surprising how long it takes to get all the coolant hot

How long are we talking Rog?

Are you still running the thinner core NA radiator? I have no idea if it would make that much difference, but there must have been a different, thicker core radiator for the TT for a reason. (I'm sure there was. I may be confused with something else though)

take the stat out and see if it still pressures buddy. had a similar one last week and it was the stat even though it didn't seem to be

As Jekyll says, remove stat and run it

A bigger radiator will just give you the potential of more cooling - on a Turbo engine you have more power, so more heat to get rid of, but only if you're really pushing the engine . . . so this isn't the problem here.

A car's cooling system is MEANT to pressurise . . . just like in a Pressure Cooker, when the pressure is increased, the boiling point of the coolant will be raised somewhat higher than 100 C. That's one of the reasons you don't want any leaks ! (and it's why the coolant will suddenly boil if you remove the rad cap on a HOT engine - because you are instantly reducing the pressure, thereby lowering the boiling point temperature)

Under normal operating, if the pressure gets TOO high then the rad cap opens and you will get coolant flowing into the overflow tank - that's what it's there for.

If your Head Gasket has failed, and you have exhaust gases getting into the coolant, you will have coolant GUSHING out of the overflow bottle! (believe me I know - I'm a Mk3 Supra owner - BHGs are very common on the 7M engine - it's why I've replaced mine with a 2JZ)

So what makes you think you actually have a problem?

If your thermostat is stuck closed then you should see that you're overheating.

To answer some of the above

Temp Gauge is smack in the middle and never goes higher unless the hose blows

Thermostat has been changed and made no difference, fairly sure the thermostat is opening okay, as the whole system get hot and when the cap is off at running temp you can see the fluid flowing

SRD TT Alloy Rad and Electric Twin Fans, which are cutting in and out correctly

Just sat on the drive, it takes about 20 mins for the whole system to get up to temp, as in the bottom rad pipe hot

And finally I think I have a problem due to 3 hoses exploding, bottom Rad pipe is rock hard, as in I can't squeeze it at all, and the hose connectors on the Hard Pipe (which is new are expanding like ballons)

I seem to be endlessly chasing the leaks around, repair one and then without even getting the chance to drive it another one appears

O and Sniff Test was planned for tomorrow morning, hence me checking everything again today before driving it tomorrow, but now another hose exploded, as in pic 1

Thankfully each hose going pop has been when I have not been in the splash area, guess there has to be something lucky with this engine

I will try running it without a Stat when I get to repair the hose that has just gone, as I have to take the Alternator and Stat Housing off to get to it anyway

Well you're clearly not overheating . . . and personally I wouldn't remove your thermostat.

And I agree that it seems strange the way your hoses are bulging (although the ones you picture are aftermarket ones)

However - if the pressure is high, as you yourself have said, your Rad Cap should be opening and releasing the excess pressure ! (regardless of the cause) - I presume you have replaced it recently?

And if the problem is a BHG, you don't even need a sniff test - if you run the engine (from cold) with the rad cap OFF you will see bubbles coming out the top!

Have you changed the rad cap Rog? First port of call if not imo or is it a aftermarket one rather than a stock toyota one?

Rad cap seems gubbed. Should be allowing the excess coolant into the expansion tank when up to temp, it's clearly not doing what it should be.

Pressure in the system is regulated by the rad cap. If you had gasket issues then the liquid would just fill the expansion tank and start leaking from there.

Wow those hoses are bulging

That's gotta be more than 1.1 or 1.3 bar rad cap relief opening pressure surely

Run it with the rad cap off from cold and see wot happens

Interesting! Have a little look here - http://www.mkivsupra.net/vbb/showthread.php?t=306362

I'm convinced my top and bottom rad hoses are over pressurised too but the consensus of opinion is that it's normal. As said on my thread, imagine pumping a bike tyre to the operating pressure of your rad cap (in my case, 1.1 bar) it will be pretty hard!

Granted though, with your multiple hose failures and bulging joiners (although they look to be unbranded silicone jobbies!?) perhaps we both have a similar problem, just yours is more advanced!?

Not sure about yours, but it appears my coolant system could REALLY benefit from a thorough flushing. Possibly a build up of sludge causing blockage / excessive pressure? Though I'd still expect the rad cap to relieve this.

Is the line from the rad to the expansion tank blocked?

Is the line from the rad to the expansion tank blocked?

That's actually a good shout! Although it'd have to be one hell of a blockage to hold in excess of 1.1 / 1.3 bar!

That's actually a good shout! Although it'd have to be one hell of a blockage to hold in excess of 1.1 / 1.3 bar!

It has to be somewhere there though. The entire pressure regulation system is in the radiator cap/overflow pipe. If you can blow through the pipe and through the overflow then it's either the little pipe that the overflow comes out of on the radiator or the radiator cap itself.

It's a very simple system and very easy to diagnose, far too much over thinking has gone on in this thread.

Well I've changed my rad cap for a brand new Toyota one and I'm pretty sure the OP has too. So I at least just need to check the overflow neck / pipe and it that's all good then I'm imagining a problem!

Would seem the OP certainly has an issue somewhere though to be splitting all these hoses. Unless all his hoses are faulty and are popping one by one?

Right been chatting with Lee and I am going to swap my stock Rad back into the car

I have to wait for Mr.T to get the hose that split last night, so I won't be able to run the car until next weekend now

There is no blockage in the pipe into the expansion bottle, I already checked that one lol

The reason I am changing the rad at this point is I have my doubts about the depth of the neck on the Rad, its seems quite shallow and I think it is fully compressing the Rad cap when it's fitted

If this is the case then the Rad Cap can not compress at pressure and relieve the pressure, this would also explain why the coolant gets sucked into the system from the coolant tank when it is cooling down, as the cap is designed to allow the fluid in through the centre of the cap, not passed the seal

This at this point is pure speculation from my end, but I have my old N/A Rad sat here, so worth a try, basically anything is worth a try at this point, as Dragonball is getting way to close

To answer someone elses question, my coolant system seems spotlessly clean inside, no sign of anything dirt/gunk wise

Rad Caps are after market, as it's an aftermarket Rad. The first cap was 0.9 Bar and Lee sent me down another cap in case it was the cap, this one is a Blitz 1.3 Bar. The extreme pressure in the system is no different with either cap

Well I've changed my rad cap for a brand new Toyota one and I'm pretty sure the OP has too. So I at least just need to check the overflow neck / pipe and it that's all good then I'm imagining a problem!

 

Would seem the OP certainly has an issue somewhere though to be splitting all these hoses. Unless all his hoses are faulty and are popping one by one?

Let's put it this way, if you took the radiator out.... there would be no pressure. If you agree that's the case then the radiator is the issue. The part of the radiator that deals with the pressure control is the cap, if you agree with this also then it's clear there is an issue at the cap side of the radiator.... for both of you.

There's no point in looking elsewhere as it's not going to be anywhere else in the system. Even if the engine was compressing straight into the radiator it would blow the expansion bottle out rather than pop off radiator hoses (when the hoses are OK of course).

People need to stop thinking zebra when they hear clip clop

Rog, your theory sounds spot on mate

Let's put it this way, if you took the radiator out.... there would be no pressure. If you agree that's the case then the radiator is the issue. The part of the radiator that deals with the pressure control is the cap, if you agree with this also then it's clear there is an issue at the cap side of the radiator.... for both of you.

 

There's no point in looking elsewhere as it's not going to be anywhere else in the system. Even if the engine was compressing straight into the radiator it would blow the expansion bottle out rather than pop off radiator hoses (when the hoses are OK of course).

 

People need to stop thinking zebra when they hear clip clop

 

 

 

Rog, your theory sounds spot on mate

Hope so Scott, but we will be finding out soon

I have found some New unused Fuel Line that is the correct diameter and has a 225psi rating, so going to put that on to replace the split hose as a temporary measure, so I can just get the standard radiator on this weekend and at least try it

This is where I am at

If water pump has failed what symptoms would it give

Jyst a thought

No pressure at all

Even when running ?