Airlocking Coolent Unless its Water!

[Dubwana]

I had a few problems with rust in the coolent pipes under the floor in my 1981 Diesel so did some repairs. To test it out I ran it for a week using only water as a coolant. (If you look at where I am its stinking hot right now so no fears of freezing!) Everything was fine so I poured out the water and added in an a coolant solution because I don't want everything corroding... and I started overheating... so Ifigured I didn't bleed it enough so I did it again, and again, and again and 10 miles up the road and again on the way back and so it went on. I figured I had done something wrong so went through the whole system and all looked good... eventually after a lot of fuss and bother decided it had all started when I put in the coolant so I flushed out the system and filled it up with H2O... and it worked great. But I was still concerned about rust so I bought a bottle of Holts Anti Rust for radiators and poured it in and now I"M AIR LOCKING AGAIN! What is going on? The Coolant was something made in the Gulf States so I figured first it was a fake product (all too commen here) made up of washing up liqued that bubbled and frothed under pressure. But the Holts little blue plastic container looked and felt original and came from a reputable dealer so I'm fairly confident in it.

Before you ask, yes I did bleed it properly. I am very sure.

I'm going now to bleed it again for the first time since I put in the Anti-Rust. If I airlock again tommorow I'll flush it out again and put back water which I know will work fine. In the meantime... Any Suggestions?

As the water cools the engine just fine is there anything that I can add that can deter rust that won't cause me to airlock?

If it makes any difference, I don't have a Thermostat in the car so its running cool by the guage inside. It doesn't rise on hills, the fan only comes on when sitting a long time in traffic on a hot day (30+) I've talked to a few people here who all say "that shouldn't happen" and I agree but it does.

Thanks in Advance

Dubwana

[syncrosimon]

Nice to here from an African T3 owner, I must say though that your problem doesnt make sense and I can see why you are frustarated, some people say that more than a 50/50 mix of coolant will prevent heat transfer, but I suspect that something else must be amiss. Not having the thermostat in would be the most obvious cause to me, as I wonder if the reduce in flow through the internal heater matrix caused by no restriction in the main radiator pipes could be the cause. Do you bleed the radiator when there is pressure in the system to force the air up and out? When you say you are getting an airlock what is happening. It is not a head gasket problem is it? I would get a new thermostat if you can and see if the restriction in the flow rate will help bleed out the system. I cannot see why adding coolant would make any difference, unless as you say it is not what it says on the tin.

Good luck.

Simon.

Lets see some pics of the dub in Africa. Is it an local registered one, or South African?

[Titus A Duxass]

I can't help you much from here but if you send a couple of air tickets I'll give a good coat of looking at.

Envious of Leipzig (0c and snow)

[Mr Bean]

I got some ideas on the subject:
I run a 14' Classic Ski boat fitted with a dry sumped and mildly tuned Ford 1600cc Xflow engine. This year on the rally rounds it overheated several times in spite of having been capable of full throttle operation for up to 20 minutes at a time while racing on Windermere prior to the Poo for brains 10MPH speed limit. Prepping it for the winter layup I checked the antifreeze and found it to be well in excess of the recomended 50% due to topping up rather than draining and filling.

Hence came my recent post in response to a members qurey:
If you read this: http://www.engineeringtoolbox.com/ethyl ... d_146.html" onclick="window.open(this.href);return false; you will find that over a certain ratio the efficacy of the mixture as a heat transfer medium falls off to a dangerous level. Or in plain english too much could make your engine boil over. I recently borrowed my mates coolant hydrometer.This has five different coloured floating disks graded in bouyancy so as to indicate degree of protection. The fifth disk simply indicated a danger. Not of freezing but of eneffective heat transfer and resulting overheating. I feel I should have one of these tools. So I don't quite understand the advice about using 100% antifreeze!

Looking again at the chart on that website I think we are looking at significant reduction of cooling effect. Notice the reference to the need for increased flow rates for higher mixtures of antifreeze. I know others will say that this effect is marginal and in a modern engine in tip top condition I may agree. But my proposition is that your engine cooling system is marginal on water and just suffers thermal run away with higher concentrations of antifreeze. I would look for blockages etc.

[Dubwana]

Simon: happy to post a picture if you tell of how! Its a german car imported by a finish guys who kept it in good condition till he sold it to me earlier this year. Its a camper and that's what I use it for but its also my daily drive. I am not that keen on putting a thermostat in because of fake parts! But I appreciate the advice and will consider it if the problem continues.

[Dubwana]

Citizen Smith: in reality I would of been marginal on coolant. It was only for rust purposes that I put it in. So I really wasn't all that serious about it. Even so very interesting observations.

[Nicola&Tony]

. . . so I figured first it was a fake product (all too commen here) made up of washing up liqued that bubbled and frothed under pressure . . .

If the coolant frothed-up under pressure (regardless of whether or not it's good stuff), could that mean that it's sucking in air somewhere? I'm just thinking out loud really, but wouldn't a sealed water system would need an injection of air in order to produce froth / bubbles?

I'd be concerned about why there's no thermostat in there. I've read previous posts on here where relatively new owners of a van have found it to be lacking a t'stat and when they put it in, the engine starts overheating.

Tony