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Gazza
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Overheating on Track

Mon 09 Oct, 2017 2:30 pm

Hey fellas, I've been having an issue that I want to post on here for posterity rather than Facebook.

On Saturday I went to the Mighty Car Mods track day at Mallala near Adelaide.  I had the most fun I've had in a long time out on the tight, technical track and I was a lot quicker than I thought I would be relative to the rest of my group.  I think they put me in the noob group because I hadn't been there before.  I have some video footage to edit and upload as soon as I get the time.

After lunch the ambient temperature started to come up, it wasn't hot but was in the high 20's.  I started to notice my coolant temperature would creep a bit and after 10 minutes on track it was just getting too high so I had to bail.  Easing off for a cool-down lap brought it back down straight away.  This happened on a couple of sessions before I gave up for the day. 

I was talking to a local dude who seemed to know his stuff (he was driving a 400 kW Skyline that he'd built himself) and he sort of said it's common, probably the thermostat etc, all good points.  But I'm not so sure.  I have had quite a bad noise that has been getting worse lately and I put it down to a dodgy idler bearing (the one for the alternator belt).  I got suspicious when I noticed after the second overheating run that there was no pressure in the coolant hoses right after the run, with the engine still running.  I popped the timing belt covers off and the back of the belt is all shiny and looks like it's been slipping on something.  So obviously I'll take the thermostat out and have a look I reckon the water pump is seizing up and unable to keep up with the higher RPM, or maybe the belt isn't tight enough?  Sorry I forgot to take a photo of the belt, I'll do it as soon as I can.  Belt and pump are only about 30,000 km old.

Any pearls of wisdom?  Maybe just hurry up and get the Mivec motor ready?
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box
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Re: Overheating on Track

Mon 09 Oct, 2017 7:12 pm

No warranties  :lol: But yeah, MIVEC will fix it. 

Is it holding coolant or is it losing it?

If it's full of coolant and it's hot, it should be pressurized. Even if the water pump isn't pumping coolant around, it should still pressurize when the temperature comes up. Maybe a radiator cap issue? 
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Gazza
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Re: Overheating on Track

Mon 09 Oct, 2017 8:34 pm

box wrote:
No warranties  :lol:

Haha it's done pretty bloody well, this motor.  It doesn't like the new 15W oil I put in it until it warms up, but other than that bit of ticking in the morning it's never put a foot wrong.
Not losing any coolant, at least not a noticeable amount.  The overflow bottle wasn't filling up.  Maybe you're right, might be worth trying a new radiator cap.  I noticed that the rubber is a little bit munted.
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Re: Overheating on Track

Mon 09 Oct, 2017 8:58 pm

It's a good (cheap) place to start before getting too carried away.

If you suspect the timing belt is slipping on the water pump, you can run the engine with the top belt covers off and monitor the temperature of the water pump pulley - a slipping belt tends to create a lot of heat in the offending pulley. The more it slips, the hotter it gets. 
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BATOOH
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Re: Overheating on Track

Tue 10 Oct, 2017 6:36 am

Put a higher pressure rating rad cap on. I think my TT was either 0.9 or 0.6 and it was blowing alot into the overflow. I have an 18 - 125 on my racer which is using a stock NA radiator. I think that means 18 psi and 1.25 bar. put at least a 1.1 bar cap on.

Also what is the condition of your radiator?? Is it really clean and free of bugs and sh**?? how many fins are bent over and constricting air flow (both sides). It's cheap to fix this as well.
 
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Re: Overheating on Track

Tue 10 Oct, 2017 9:55 am

If it's hot and there's no pressure in the radiator (known by squeezing the top hose), then you've got a leak but not only that, your boiling point is a bit lower.


It's either going to be a faulty radiator cap which is easy to check

or

The seal on the pump that's gone.



But you need to check for loss of coolant first because any leak anywhere will give a loss of coolant.


Worst case situation is that the head gasket has a leak internally, if it's going to happen, it's going to happen when you push the car hard, cylinder pressure will push coolant out of the cap, when you shut it down, you've lost coolant so there's no pressure in the rad.
The next thing that happens is that due to excessive pressure in the cooling system, coolant gets forced part the pump seal, the bearings rust, then the pump seizes, taking with it all 24 valves.


It DOES happen.


If you catch it early enough, it's an easy fix by re torquing the heads.
quote from barryboys.
Yes, yes, yes, that might be so, but you're clearly missing the bigger picture.....
4 intercoolers!!!!!!!!
Beat that!!!!
 
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Gazza
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Re: Overheating on Track

Tue 10 Oct, 2017 1:27 pm

Thanks guys, I've got a few things to look at next time I see the car. 

Maybe it has lost coolant, but you can normally spot where it's leaking especially if it's coming from the radiator cap.  There were no drips of any kind under the car between track sessions.
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Re: Overheating on Track

Sun 12 Nov, 2017 7:43 am

magn1t wrote:
If you catch it early enough, it's an easy fix by re torquing the heads.

I'm really interested in what you find with this Gazza. The GTO body I got as a spare had a rooted engine courtesy of a young guy with heaps of crap mods on it, I see yet another "head gasket blown" being done on F/B at the mo. Easy to kill Turbo GTO's if you get them knocking and lift the head, and I have a theory to ponder and some advice I was given by a wise old racer. Theory- When Torqueing the TT heads to 90 ftlbs it's quite a vigorous work out getting them up there isn't it. Add to the difficulty of the hex head bolts especially if you don't have the dead right socket on the end of the torque wrench. I think the NA GTO is 80 and the Turbo is 90. Correct me if I'm wrong. So torque wrenches (but more so the actual user) also come in different types and calibration/accuracy. So it would be easy to see variances of plus or minus 10% I would say (without extremes). so some GTO turbos might not even get torqued to 80 ft lbs. easier to lift heads then. especially if you are blowing 18 psi with a bit of knock...
I was advised to "screw em up - wind them down to 110 ft lbs - the bolts will take it". So when I did the head gaskets on my race car a few years back I screwed them up to 90+ ft lbs. I have an old flex bar Torque wrench that was the old mans. I used ACL composite gaskets (I think- can't remember- think I kept the  paper label out of the shrink pack though). So I haven't really adopted this advice as yet. However before I set boost at 20psi when I put the tunable ECU in, I will remove clean and retorque the heads to 100+ ftlbs, and we shall see what happens! I may eve replace the water pump with a top brand name one!
So I'm interested to see what you find out here.
 
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Gazza
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Re: Overheating on Track

Sun 12 Nov, 2017 5:50 pm

OK so it's become clearer over the weekend what's going on.  The first thing I did was replace the slightly dodgy radiator cap with 16/110 one, which is one step up from the original.  What that did was make the leak much worse  :lol:

I pulled the timing covers off and the first thing I noticed was the water pump is leaking all around the edge, so it's probably my own fault for using too much RTV or being too slow or something when I installed it.  The weird thing is it's held up fine for several years, about 30,000 km and a bunch of track days.

The next thing I noticed was the timing belt.  I thought it seemed a bit loose but these things are a bit of a pain in the arse when it comes to tension.  One minute it's about to fall off and the next it seems fine, I assume depending on the position of the cams and the direction of force on them from the valve springs.  What I did was fire it up and give it some fairly serious revs to see if I could figure out what that noise was that I was getting.  Above a certain RPM the belt starts to slap around on either side of the water pump, so that's not good.  It's possible that the water pump is starting to sieze and is creating a point of resistance on the belt, the higher the revs the more it resists until it slips?  Anyway it's a bit of a sh!t-show so I'll have to pull it all apart.
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Re: Overheating on Track

Sun 12 Nov, 2017 6:23 pm

Got it just in Time I hope. Post mortem required.
 
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Gazza
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Re: Overheating on Track

Sun 12 Nov, 2017 6:30 pm

It never got really hot, I made sure to button off when it started to rise above normal.  So hopefully the head gaskets will be OK.
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Re: Overheating on Track

Mon 27 Nov, 2017 12:00 pm

I suppose I should update this.  Last weekend I pulled the pump out and found that it was leaking from a couple of spots in both gaskets.  It was immediately obvious to me that I had used far too much silicone RTV when installing it last time and the bolts were not very tight at all. 

I pulled it apart, cleaned it up with a green kitchen scourer and turps (didn't have any kero) and cleaned up the block.  This time I used a syringe to suck as much coolant out of the block as I could so that I could properly dry the areas around the ports.  I found that proper parts are much harder to come by in Australia so I couldn't get a pump, housing or even a gasket for any of it.  The usual story, Repco had it "in stock" only it was clearly the wrong everything when I took it out of the packet.  For that reason I had to cut my own gaskets out of gasket paper, and I used that brown aviation gasket sealer that comes with a little brush.  Torqued everything up, filled it up and did the belts.  I fired it up the next day and went for a good long drive and no leaks.  It's still going strong and hasn't dropped any fluids so I'm calling victory.
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Re: Overheating on Track

Mon 27 Nov, 2017 8:16 pm

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How's the Mivec build coming along?
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Gazza
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Re: Overheating on Track

Mon 27 Nov, 2017 9:56 pm

I've located the valves, which were fortunately still in their little position-indicating device.  The springs, retainers and collets are all there as are the new stem seals.  So I have the first head on a bench at work waiting for the arrival of an extension thing for the valve spring compressor so I can start to assemble it.  Somehow I have to figure out how the cam trays and sh** go back together...
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