Rad Cap

[Guest Brian T]

Hi , I got my car MOT'd last week and Taxed as from Sunday, Sunday afternoon I covered about 30 miles in 3 different little run outs, never really driven the car before so kept it local. Getting towards the end of the third run I noticed the temp gauge sneaking up towards 3/4, got home and put the car back on the drive and as the heat was transferring from the block to the coolant the overflow pipe started to spew out Uniparts finest pink stuff

 

When it had cooled a bit I refilled the rad, about 1.5 litres total, and had a look on here and other sites for inspiration, it seems overheating is a fairly common problem with Exmos and an electric fan is the way to go. I went off down the breakers today and got a fan from a Mitsubushi and an expansion bottle from a Hyundai Accent (?), also grabbed the Hyundai fan just in case, a fiver. Got them home and flashed the Mitsi fan up on a spare battery, works fine, managed to mount it , not wired it in yet though. Viscous fan is now obsolete.

 

The wiring of the fan should be OK thats easy enough , but , what I would like to know is this, does anyone know of a rad cap that will replace the original rad cap , the existing rad cap is the standard blow off type with no provision for drawing fluid back from the expansion bottle under vacuum. I believe the rad is a Cortina ,copy maybe as it is plastic at the top, same as the one shown on GBS/ Kit spares website ?

 

Any info or options would be much appreciated.

 

 

Cheers.

[richardm6994]

I seem to think I have a "suck and blow" (pmsl) rad cap kicking around the garage which would suit your rad and I don't mind sending to you if you want it. It's also rated for water higher pressure than standard caps.

 

Just a few pointers which I have learnt over the years with my exmo;

 

1) If you fill the cortina rad right to the very top, natural expansion will blow out more coolant than you'd think (it normally leaves about 1.5 inch air gap in the top of the rad).

 

2) Blown head gasket can result in water being pushed out of your overflow (exhaust gases pressurize your coolant system).

 

3) When looking into the air flow onto the rad......remember that getting hot air out of the engine bay is just as important as getting cold air into the engine bay (something which is always overlooked). The air flow through your rad will always be restricted by the pressure differential between the "air in" and "air out". On a side note, my over heating problems dissappeared once I put some louvres in the side of my bonnet (near the front of the car) to help expell hot air away from the rad.

 

hth

[Guest Brian T]

Hi Richard, it shouldn't be a blown head gasket, very recently rebuilt engine, about 3 hours running.

 

As for the airflow for exhausting the hot air from the engine bay, the air scoop on top was a dummy when I collected the car but now has holes in the bonnet which should allow heat to vent when stationary and hopefully force cool air in whilst in motion. I've got some side vents on order, going to fit those facing backwards in the hope it will create a venturi effect while driving and partially drag some of the hot air out.

 

I may fit more than one pair thinking about it !

 

The old crossmember and other metal work in effect blanking a lot of the core doesn't help especially being so close to the rad.

 

Will have a look around some other breakers in the area today, we're still a snow free zone, and get back to you regarding the rad cap, thanks for the offer either way.

[richardm6994]

Hi Brian,

 

Glad it's not a head gasket.......that's the last thing you need at this time of year!!! The vents you've mentioned should help massively. Have a look at my photos and you'll see were I located mine which works very well.

 

Without teaching you to suck eggs (plz forgive me), when the car is in motion, you have to both force air into the engine bay (in front of rad) and suck it out (behind the rad). All air flow must travel through the rad to gain most cooling benifit.

 

Forcing air into the engine bay behind the rad doesn't really help with cooling (when the car is in motion) as it creates air pressure behind the rad which hinders the air trying to flow through from the front of the rad.

 

On the plus side......your bonnet scoop looks awsome!!! and will help supply your carbs with fresh air.

 

 

I have been fortunate enough to be able to do some fluid dynamic analysis on some software we use at work (based on my exmo). This has shown that the RH's nosecone easily provides more than enough air to the rad, but the main restriction is air flowing out of the engine bay (based at 50 mph). Even slightl increase of the air out of the engine bay, such as the louvres you plan to put on can improve cooling massively!

 

I have the same cross memebers blocking the rad on my exmo, and although these are not ideal, they don't cause a great deal of problems if your air flow is okay.

 

At the end of the day, these are not F1 cars!! so it doesn't have to be that complicated..... Just keep in mind that the air flow rate "in" must equal the air flow rate "out" and that the only air movement which significantly benifits engine cooling is that which travels through your rad.

[Guest Brian T]

Happy Easter Bunny here. On my way to the breakers I called at the accessory shop to get an illuminated switch, fuse and other bits. Asked if they had any rad caps that may do rather than go trudging round the breakers in drizzle, he had a box full of old ones so I had a dig around and found one the same size,fit, poundage (13lbs),AND it was a "suck and blow" one ;-) Absolute bonus to it was the fact it is new old stock, price on the package? £3.25 !

 

Two hours later saw the lot fitted and the engine running up to temp, the cap allows the excess out just fine, the fan brings the temp down nicely and the extra fluid in the expansion bottle gets sucked back in as it cools, in the words of Liam Gallagher "Sorted". I'll be fitting a variable temp thermostatic switch kit next week when it's in, damn the extended weekend, I believe I can retain the manual switch as an override by "piggybacking" to the relay post that triggers the relay so not a waste of money.

 

Was hoping my vents may be here today but alas Mr Postman gave us a miss. Probably next week now.

 

Now I've got to find something else to fiddle with,ahem, I mean improve