Overheating - Again! Thoughts?

BackinaBX · Post by **BackinaBX** » Thu Jul 20, 2006 12:57 am

Hello again forum.
I like to think that time away from here represents trouble free BX ownership. As always though... I'm back with another stumper of a question.

You may remember I posted here a few weeks ago regarding the red-temp light and STOP light combo I had when working hard up a steep hill.... well, it's back.

Three times over, in fact. Now:The Facts. My red temp light and STOP light combo only come on when I'm going up either a steep or a long hill. It happened twice in two days on the same stretch of motorway into Bristol (M4 from the M48 to the M5 interchange if anyone knows it). And once in the hills of South Wales. All times I wasn't exactly caining it along. I guess I was doing about 65 and 40 respectively.

When I stop the car, I can hear the fan running... so that's OK, but opening the bonnet there's some steam coming from somewhere that quickly dissipates, so I can't track it down. Sometimes I can hear the coolant boiling in the filler next to the rad.

Does anyone have any ideas? At the moment, after having four new tyres and the rear arm bearings, she's running like a dream... apart from this frustrating and seemingly occasional cooling issue. I say occasional because today I did a 180 mile round trip in 35 degree heat and guess what... nothing happened at all. Perfect running.

HELP!

DavidRutherford · Post by **DavidRutherford** » Thu Jul 20, 2006 7:24 am

I think you may have a partially blocked/choked radiator. It's working under normal cooling requirements, but when you ask that little bit more of it (hill climbing) then it cannot provide enough cooling.

Would be worth removing and washing through with an aggressive detergent/ ionic surfactant. Make sure it's THOUROUGHLY rinsed through before refitting though!

BackinaBX · Post by **BackinaBX** » Thu Jul 20, 2006 8:01 am

I was coming to that conclusion... and I was going to give the car a minor service this week, but it's too damn hot to be outside wrestling with locked up nuts and bolts... however, I'll get some of this stuff and flush out the rad, and the the rest of the cooling system while I'm at it.

Thanks for that one!

DavidRutherford · Post by **DavidRutherford** » Thu Jul 20, 2006 8:18 am

If you're going to flush the whole cooling system, then use something like Holts speedflush or some other designed-for-the-job flushing agent.

I would only use an aggressive detergent (or similar) on the rad if it's removed from the car. Chemicals like that will cause havoc with the dissimilar metals in the engine. If there's even a bit left in there it is likely to set up electrolytic corrosion, and make a right mess.

You may also find that the rad is beyond cleaning. Some rads I've tried cleaning before have been bejond it, so I fitted a replacement, and then for interest cut the old one open. The crud in them has to be seen to be believed. 1/4" thick in places.

Brian · Post by **Brian** » Thu Jul 20, 2006 9:12 am

Hi,
Yes, I concur with the radiator suggestion...

Check for any cold spots in the rad after the thermostat opens.

With this cross flow design, it has a much greater chance of blocking when compared to the vertical design with a header and bottom tank.

This would collect most of the crud and not deposit itself in the cooling tubes.

I know the change of flow was a result of the car shape that evolved due to computer design, but I still see no reason not to have the tubes vertical.

Yes I do, will reduce the profits for the Radiator Manufactures.

AndersDK · Post by **AndersDK** » Thu Jul 20, 2006 1:07 pm

Read about a well hidden radiator issue here :
http://www.bxclub.co.uk/forum/viewtopic ... highlight=

jeremy · Post by **jeremy** » Thu Jul 20, 2006 10:01 pm

I think the cross flow radiator was fitted when computers were very rare and occupied whole buildings - certainly before CAD was used or for that matter invented.

My recollection is that the Rover 3 litre had one (1958) - which I suppose puts paid to the thoery that they were fitted to low and sleek cars. Jaguar Mk 11 had a conventional one as did the E types - or certainly some. Jaguar XJ6 (1968) certainly had a crossflow as did Triumph Stags (1970).

The other interesting bit of radiator design is the aluminium core - which I think first appeared in the Lotus Elite (4 seater 1973 2 litre one - not Coventry Climax engined 1960 one). Its attraction was its light weight and good efficiency. The volume of Lotus sales wouldn't have been sufficient to justify large scale investment - but I suppose valuable experience in the manufacture and use of the things would have been gained.