Coolant woes

[cockers]

Either my car has just had its first real problem or I’ve been a total knob.

I was trundling along (engine still cold), when all of a sudden a load of steam/smoke came pouring out of the passenger side slat in the bonnet. Pulled over straight away and shut off the engine. Popped the bonnet – no blue cap on the coolant tank and the level was way down (NB – it’s a 94L 4.0 litre, so just one tank).

Topped it up with water and what little spare coolant I had, fired it back up (heater on full blast) and drove home – temperature stayed just below 70, as it has been all day.

The thing is, I had checked the level of coolant at the weekend and it was fine. Since checking, I have done about 50 miles.

Could it be that the cap blew off the tank under extreme pressure? It seems unlikely to me, given that the engine was cold and that there isn’t coolant sprayed all over the engine bay. However, if it did, what could be the cause and what should I do about it?

I am now wondering whether I was a total plank, forgot to put the cap back on when I checked the level at the weekend and have been sloshing coolant over the sides all day – the steam could have been coolant hitting the manifold, but it hadn’t done it up until this instance.

Either way, I need a new pressure cap. I know it’s a VW/Audi part – can I get it quickly from a TVR dealer or am I more likely to find joy at a VW/Audi dealer? For info, I need the car by Thursday, as I’m going up to Blackpool for a factory visit! I guess I’ll have to do the whole bleed and refill routine, as outlined in the manual as well.

Look forward to receiving any help/opinions you guys have, even if it means I have totally embarrassed myself and lost any credibility I might once have had.

Cheers,

Paul.

[GreenV8S]

quote:Either my car has just had its first real problem or I’ve been a total knob.

No comment (!) but if have a very careful look around the engine bay you might, just might, get lucky and spot the cap somewhere lodged in a corner. The system simply won't hold enough pressure to blow the cap off. It's very unlikely that it has unscrewed itself when done up tight, but since you've ruled out all the other credible explanations that must be what happened. Yup, that's the only possible explanation.

Cheers,
Peter Humphries (and a green V8S)

PS next time when you take a cap off, put it somewhere that will be obvious if you try to shut the bonnet. I usually rest it on top of the driver's side wiper blade, clean side down. I figure even *I* won't likely drive off with that right in front of me.

[JonRB]

Otherwise, pop into your local friendly VW/Audi dealer and buy one off the shelf. It was £10.33 inc VAT last time I bought one (a few months ago).

The part you want is "Blue Rad Cap p/no: 443121321"

>> Edited by JonRB on Wednesday 13th February 10:04

[cockers]

Fantastic! This is what makes PistonHeads so great.

You two have saved my life:

Peter - my heart rate has dropped back to normal

Jon - A trip to Martins VW/Audi in Basingstoke (about two miles from where I live) will get me back on the road (had to get the bloody train to Reading this morning, because the missus needed the 106 more than I did).

As you may have gathered, I'm a technical know-nothing, so I can't express my gratitude to you both enough.

Regards,

Paul.

[JonRB]

Funnily enough, it was Martins I bought mine from as I too am just a few miles down the road from them. I didn't have a part number then, so I just slapped my old one down on the counter and said "I'd like one of these please". They were quite bemused when they asked what car it was for and I replied that it was a TVR.

Incidentally, I went to the Audi side of Martins to buy my cap. Its a little door on the side of the building, the side that Hatch Lane (coming from Old Basing) comes down.

[macca]

Cockers, your're a total knob and so am I! I left mine off and drove a good 10 miles or so but didn't lose any coolant, I was gobsmacked that it didn't come out when hot - can anyone explain this?

Glad you sorted it!

[cockers]

quote:
Cockers, your're a total knob

I know. God, do I know

Jon - same here. I phoned Martins and said I needed a part for a TVR and he said "riiiiiiiiiight" in a kind of "so why the hell are you speaking to me then?" type way. Once I'd explained, he seemed amused that our beloved TVRs had a VW part!

I didn't get into all the other bastard love child components we take for granted. Could have been on the phone all day...

[yum]

You say that there isn't one but mine is a '94 4l and does have one higher up. It has a brass bolt on the top and should be full. Presumably your engine is pre-serpentine (ie a thin v-shaped fan belt rather than the wide, flat variety).

You should also check that the radiator does not have an airlock in it now, which may account for the apparent non-loss of coolant. The way to do it (on mine, anyway) is as follows;

Undo the brass bolton the upper tank, top up to the max. Leave the blue cap on the other.

Undo the bolt on the top off side of the radiator. wait until all of the air has been forced out by incoming water. Do up the radiator bolt

then top up the higher tank again, AND DO THE BOLT UP.

Finally check the level of the lower tank, not forgetting to.....

There will be a slightly different procedure for that if you really only have one tank, but do it anyway.

Good luck

Richard

[kevinday]

Although the water expands a bit when hot, the pressure cap is there to allow the water to get beyond boiling point without actually boiling, the increased pressure caused by the water expanding and compressing the air in the header tank, rad etc. stops the steam/gases releasing from the water thus not actually boiling.

[cockers]

Yum,

Cheers - I'll be doing the refill, undo radiator bolt, etc business tonight or tomorrow a.m. It's all spelled out in the manual and seems perfectly simple.

Yes, it's pre-serpentine, but there is only one tank - no upper tank and no brass bolt.