Engine 850: B5234T/2.3/20v/T5: heater matrix explosion at high rpm

[Luke Rsh]

How do, been a while since i've been on here! question for you wise lot. I've got a 95 850 t5, 189k on the clock but new engine at around 100k. Today, there i was, merrily hooning along and let loose on the rpms a little bit (around 6500) and lo and behold, suddenly i've got a car full of vapourised coolant. whoops. limped home ( fortunately very close) and as expected, the floor pan has the entire coolnat reservoir sloshing around in it, pulled the heater matrix out and the top plastic was bulged out completely, blown from the pressure. I've ordered another plus sundries, but for the mo, bypassed the feeds. refilled, engine running fine, no water in oil, no oil in coolant, but I'm pretty concerned i've got a blown head gasket.

Would one expect the coolant pressure to increase enough at high rpm to blow the matrix without exhaust gases in there?

Is there any other way to test for a head gasket exhaust leak into the water jacket without pulling the head?

Any ideas, experience etc would be massively appreciated, I'm a bit stumped here as the only head gasket failure i've ever encountered was quite a lot more obvious!
Many thanks.

[4x4]

Take it to a garage and ask them to do a sniff test on it

[Luxobarge]

Probably just one of those things - I'd expect that coolant reservoir cap to release the pressure way before the matrix let go, so other than perhaps replace the cap (or at least check it) I'd relax, probably nothing really wrong, you were just unlucky.

Coolant cap should be green by the way, the grey ones are known to go faulty.

[Luke Rsh]

thanks - yup, i've ordered a new green coolant cap ( the old one was grey). I guess the heater matrix was probably either original or very old, it looked it, so i'll try and switch it out, replace the o rings etc, cap, pop down the garage and get a sniff test? what causes such a high pressure jump at high RPM if not exhaust gases?

And...anyone got any tips for getting 6 litres of ethylene glycol coolant out of the floor mats and foam?

[RollingThunder]

Must admit I've never heard of one failing quite so spectacularly like that - they usually weep for a long time before the corrosion affects its structural integrity.

I'd be very suspicious of a HG issue, but you may be lucky and just have the old grey cap causing the pressure build up. Fingers crossed!

Re coolant cleaning... well I pulled the carpet out of my old Discovery when its matrix leaked badly - the blue coolant stained the carpet permanently I'm afraid. I tried a domestic carpet cleaner, a jet washer and various stain removers but I never managed to get rid of that last trace of blue. I ended up replacing the carpets...

[Pupbelly]

Based on Mr Thunders experience this item may be of use on eBay right now; item number: 393516319427