New engine overheating - clever people HELP

[v8jimll]

This is driving me potty! My 4.3 pre cat has just had a the block relined by tvr power. Engine rebuilt by my self, water pump working, thermostat removed, radiator recored, no pipes kinked, ignition timing set at 28 degrees before top dead centre at 4000rpm. After driving two miles from cold, the rad fans come on at about 95 to 100, left to idle after this the fans still run reducing the temp a bit but are still running after five mins and temp guage still reads 93 plus. Can any of you gents help me? got any ideas? Cheers James

[RFC1]

Got to be a complete blockage somehow, or perhaps an airlock? After 2 mins the otter/fan switch must be being given a *false* command to turn on ? Dont mean false as in not bloody hot, but it must be in an immediate hotspot....

[spend]

Up the revs to 2000rpm & see if that fixes the problem, if so it's a flow problem.

Easiest way to diagnose is take temps around the cooling system with an infra-red thermometer IMHO.

Still make sure the fan belt is nice & tight.

[Barreti]

How did you fill it? Its awkward but you need to ensure water gets to the pump so you'll need to have removed the top swirl tank hose and poured water down there directly into the pump.

[Rob_the_Sparky]

Quinny said:

Barreti said:

How did you fill it? Its awkward but you need to ensure water gets to the pump so you'll need to have removed the top swirl tank hose and poured water down there directly into the pump.

Thats exactly how I do mine

Back fill from the top hose

I wish I knew that when I did more recently! Given the job I've had getting all the air out of the system (still not 100% sure I've finished!) my vote would be on an air lock.

The (slightly dodgy) technique I've used recently is to let the engine warmup and get some pressure in the system. Usually get the fans running, open bonnet and wait for them to stop. Then stop the engine and very slowly release the pressure, the expansion pushes out air from the top of the swirl pot if there is any in there (you have to move a volume of more than the pipe from the swirl to the expansion to push any air out of the swirl). If engine is cold then squeeze the top hose flat with both hands and this will also push a little air out of the swirl pot (one handed does not move enough volume).

Not sure if it is significant but I found that my pressure cap was holding less than 3 psi so got a new one from GSF (£2.50!, Blue Coolant Cap thread for part number).

Rob

Edited by Rob_the_Sparky on Thursday 5th August 19:07

[gateeast]

I was told that the thermostat removed doesn't cool the engine, quite the opposite. The thinking being that the water passes to fast through the radiator no allowing time to cool it down?

Not sure if this helps.

[v8jimll]

Quinny said:

From a cold start, With no thermostat fitted, you should be able to remove the swirl tank cap and watch a nice flow of water from the top hose.... With a few revs it should be Gushing through... If this isn't happening you've got air in the system

Thanks for this tested it today and working as you have described so i hope that air lock is ruled out. I am wondering if i should be looking at the recon rad, but have no idea how to quantify its cooling ablity.

[v8jimll]

spend said:

Up the revs to 2000rpm & see if that fixes the problem, if so it's a flow problem.

Easiest way to diagnose is take temps around the cooling system with an infra-red thermometer IMHO.

Still make sure the fan belt is nice & tight.

Did this and unfortunately just raised the temp, fan belt is tight, do you have any idea what temps i should be getting when i take temps around the system?

[v8jimll]

Barreti said:

How did you fill it? Its awkward but you need to ensure water gets to the pump so you'll need to have removed the top swirl tank hose and poured water down there directly into the pump.

Howdy, i have been filling through the waterpump to heater matrix hose, but i would imagine that now that the thermostat is removed the flow should be free? Or am I talking plop?

[spend]

Rev it and feel if the top hose pressurizes, does sound like the rad may be silted up - should see @10C difference across the rad (less maybe depending on how strong your fans are?) IMHO.

[JKY]

Did you replace the temp sender during the rebuild? If so then the scaling could be out and all could be working correctly, just showing an incorrect temp.

[v8jimll]

Quinny said:

Mmmm

Well if you're getting a nice flow, that means the water is passing through the system...

So, it could be that the radiator is just not disipating the heat, or the temp gauge is telling lies...

Are the fans running in the correct direction??

As the radiator has been recored and it has 39 cores now against 27 previously and the old core was approximately 25% blocked, i am finding it difficult to flame the rad, the little man who fixed it would have to have really ballsed it up! Will check the fans- interesting idea....

[v8jimll]

JKY said:

Did you replace the temp sender during the rebuild? If so then the scaling could be out and all could be working correctly, just showing an incorrect temp.

The otter switch and temp switch have not been changed, however they both agree with each other, even if they both had failed the fans run for ten mins plus at idle(not waited longer than this). how long do they normally stay on?

[JKY]

My experience and set up is the same a Quinny, I also have a slow and fast speed mod on my fans and slow speed comes on quite regularly and tends to stay on a fair while, however very rarely comes on full speed and soon turns off again.

btw, my car has actually sold now so this is all 'had' rather than 'has'......

Edited by JKY on Sunday 8th August 15:17

[Rob_the_Sparky]

JKY said:

My experience and set up is the same a Quinny, I also have a slow and fast speed mod on my fans and slow speed comes on quite regularly and tends to stay on a fair while, however very rarely comes on full speed and soon turns off again.

btw, my car has actually sold now so this is all 'had' rather than 'has'......

Edited by JKY on Sunday 8th August 15:17

Got any more info on the two speed fan set-up, is that an aftermarket mod?

Rob

[carsy]

Rob, the two speed fan set up is supplied by mod wise.

[Guillotine]

have you got the cowls on the rad? If not the fans are only drawing thru 1/2 of it.

Also, water wetter helps clear airlocks etc by breaking surface tension. It also reduces temps by around 5 degrees by the same process.

A