MKIV BHG's...

[Alex]

Don't panic yet, just asking questions!

 

OK if it's a blown head gasket to test I need a compression test and a sniffer test. Which I will be getting done soon.

 

In the mean time. The car overheats when A) its driven too hard for a short while, or B) driven at speed say 70+ for more than 5mins.

 

Now that can't rule out a BHG, AFAIK...but what I think does is the fact it doesn't cool down if I slow down it takes actual down shifts which force more water round the system. Suggesting that its a flow problem, and the biggest factor in flow would be the radiator...

 

The system has been flushed numerous times and is not chucking out much dirt anymore. But what particles do come out with the flush are the consistancy of fine sand.

 

The car is worse when not using the cabin heaters and with the oppresively hot weather of the last two days its been a right pig.

 

I'm trying to arrange a new rad but spending more money on a car I want to sell is getting to be a right pain in the wallet.

 

But, if I did have, say a Cylinder to cylinder BHG which obviously would not contaminat the water or oil then what sort of symptoms shoulf I get? And does the above make sense?

[Steve Cargill]

I can describe what mine was line, but I also had a thermostat stuck open at the same time.

 

I'd drive 100 miles to work - sedatly with a few squirts - when I got there the expansion tank would be full. After the engine cooled down it was empty and looking in the radiator cap you couldn't see water. Temp gauge never went about 1/4.

 

If I drove hard for 5 mins or so - dual carrageways and roundabouts with lots of WOT - the temp gauge would go right up to max when the power was on then drop down to 1/2 way in about 5 seconds. I could lose the water in 5 mins driving like that.

 

Two garages did sniff tests and the both came up negative (i.e. no problem) I think one also did somehting wiht the cylinder, not sure.....

 

Eventually it blew big time...... After that it had blown through to the waterways on 4 & 5 I think.

 

Edit - I think Chris W has an more accurate way of checking than a conventional sniff test.

[Steve W]

If it's Cylinder-to-Cylinder, then you'd lose Compression/Power misfire/'fluff'

but not really temperature rise ? !

 

The High Temperatures from BHG's is because you're losing water

- (and you're not ?) = not enough water & Air-Locks, or lack of circulation.

 

The other obvious sympton of water-loss-type-head-gasket is out of rad/header

tank OR out of exhaust.

 

ie. for the temp' to rise the BHG has to cause WATER problem one

way or the other (pressurising cooling system or 'burning-off' water)

 

One of the others (or several) said water pump ? That might also

tie in with the 'needs revs' to cool down bit ?

 

Using heater-matrix will help it cool wether it's rad/pump OR BHG

, it's just giving it more effective rad area.

 

[ Get the gas-test done, it should rule-out/confirm cylinder-to-waterway. ]

 

If you're NOT losing water then RAD still seems likely (especially

the hotter-the-faster bit, we've had cars we just put new engines

in sitting in the garage for hour OK then pulled out onto road and

'Up She Goes' within 100yards - the cooling system 'copes' until

you start moving then it NEEDS the rad )

[Alex]

Replaced the water pump and thermostat already so I think we can rule them out.

 

If the viscous fan wasn't spinning fast enough would it make a major difference?

 

I don't think I'm losing water but then I am flushing it every weekend so each week has a settling down period.

 

One thing I have noticed is that the red coolant from Toyota makes it even worse...I read on the back of a water wetter bottle (which I tried last week to no avail) that 50/50 water/glycol (antifreeze) runs upto 8degF hotter than just water...how cr@p is that!

 

Anyway I'm again more confident of ot being the rad which is settling my nerves.

 

My partners dad says he's got a development rad for the elise 190 which may fit the car (well long enough to test the system (and if it works this freeby will be installed on a more permanent basis) he'll even get a couple of leccy fans sweet!

 

I hope it fits!

[Adam W]

Plus or minus eight degrees should make no difference at all in a properly functioning system, your problem is occurring because something is not working as it should, not because the type of coolant you have is making a 1 or 2% difference.

 

You might consider getting a leakdown test done, which is a "better version" of a compression test. Anothwer way to check if a HG has blown into a waterway is to fill the rad to the very top and remove the rad cap, then fill the cylinder with compressed air using an airline and an adaptor which screws into the sparkplug hole - if air gets into your system from a leak then your rad will overflow.

[Guest Terry S]

Alex, did you ever change the cap??

[Alex]

I did indeed replace the cap...found out mine wasn't the stock item (only .9bar rated and not the 1.1 bar stock job)

 

Adam,

Yeah I know it just seems wrong that proper COOLANT runs hotter than water. I'll keep the leakdown test in mind...

 

Thanks all

[Steve W]

I'll try to find out from an expert (IF I can find one !),

 

BUT, I would have said that alcohol would be a BETTER heat-sink

than water - not sure though - I'll find out.

 

[ anyhow - NEED to run anti-freeze as corrosion inhibitor, so, although

it could be true, not really a proper answer ].

[Chris Wilson]

You cite text book blocked rad or iffy viscous coupling probelm there!

 

Best guess is rad, followed by viscous coupling knackered, both assuming undertray and fan shrouds are present and correct.