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Water pressurising and venting, kent engine
steve m - 25/3/15 at 05:16 PM

Hi all

I had a thread going a week or so, as I had water problems on my new rebuilt crossflow, once the engine got hot, it would vent out of the radiator cap a lot of fluid couple of pints at least and steam, until engine switched off, so I bought a new cap, and it has done exactly the same today

I had pressure tested the water system , with a home made bit of kit, and on a cold engine full of water and pressured up to 12lbs
the following day, still had 12lbs

ive pressure tested all four cylinders with valves closed, and again no leaks into the water system

whole water system is clear of any obstructions and if I back flush from any direction / hose we get a healthy flow out the other end

there is no water in the oil, as I thought there was, but could be a very thin layer of oil in the water

The only thing I have noticed is that even when ive got steam. and water pumping out of the radiator cap (mounted on the engine) the top hose is not particularly hot, just warm

The thermostat is the same one I had in last year, and worked fine then, but I will get another one

I am not a newbie to this crossflow set up, and have been changing engines quite regularly over the years, but this problem has got me stumped

help!!

steve

britishtrident - 25/3/15 at 06:19 PM

Try drilling a couple of 2.5 mm holes in the thermostat also check the ignition timing.

David Jenkins - 25/3/15 at 06:49 PM

^^^^^

What he said... it's possible to trap air under the thermostat after refilling the engine, and this also means that the engine's heat sensor is in a bubble of air.

A little hole or two in the thermo housing allows the air to pass through, but doesn't materially affect the flow of water once the thermo opens.

steve m - 25/3/15 at 07:00 PM

thanks guys, good idea's !

steve

Dingz - 25/3/15 at 07:11 PM

Is it possible to fit the thermostat the wrong way around on a crossflow?

rusty nuts - 25/3/15 at 07:29 PM

Do you still have the heater hose from the inlet into the water pump? It helps to bleed air from the highest point of the cooling system , I fitted a bleed point between my manifold and the heater as well, have never had any problems

steve m - 26/3/15 at 07:06 AM

The thermo is fitted correctly, but certainly worth a shout, but im wondering if it is actually opening, even though it was new last summer

I do have the top heater hose, that goes from the manifold to the top of the water pump, and that was bloody hot, so I presume it was filling up with water, could of been steam though !!

steve

David Jenkins - 26/3/15 at 08:37 AM

The main thing about getting air trapped under the thermostat is that the wax capsule in the thermostat never gets into contact with the water, which stops it opening.

907 - 26/3/15 at 11:01 AM

A mate of mine, Stewart, has a 1971 Lotus that used to boil.

His problem was that the rad caps come in differing depths, and he had the deeper rad neck.

He'd bought a new cap to solve the problem but that was the same as his old one, and when fitted
it didn't compress the spring enough. Although it was rated higher, when fitted it would blow at 1 or 2 psi.

He did a bit of searching the shelves at Halfords and solved the problem.


Paul G

adithorp - 26/3/15 at 11:18 AM

Once you've eliminated an air lock as the issue, I'd suspect the head gasket (and I'm not usually the first to jump on the HG band-waggon).

I know you've put pressure in and it held but only 12psi; Compression will be more than that and I've had it before where pressure testing showed nothing. Try, release all presure from rad and refit cap, start and run for 30sec-1min, switch off and then remove the rad cap (carefully, there shouldn't be any heat but you never know). If there's any pressure you have a h/gasket issue. You could also squeeze the top hose from cold and if you feel it build pressure in the first few mins...

britishtrident - 26/3/15 at 12:09 PM

The currently favoured way to test for head gasket failure or a cracked head or liner is to sample the gasses present in the coolant. You can either get your friendly local MOT tester to do this or buy a chemical test kit off ebay.

Another way that sometimes works is do a 100psi cylinder leak down test on each cylinder and look for bubbles in the coolant.

All the other test methods tend to be a bit iffy unless the gasket failure is massive.

[Edited on 26/3/15 by britishtrident]

Norfolkluegojnr - 26/3/15 at 12:54 PM

quote:
Originally posted by britishtrident
Try drilling a couple of 2.5 mm holes in the thermostat also check the ignition timing.



This. made a huge difference to mine.

steve m - 26/3/15 at 01:08 PM

I have taken the new thermostat out, and put it in a cup of boiling water, and nothing, its stuck

but the old rusty one did move, and now has two holes in it,

Now that the rain has stopped, im off outside for another idle test

steve

threadbare wallet - 28/3/15 at 06:49 AM

Fingers crossed the holes in mine sorted the very same problem.if not try it with the thermo to see if that sorts it? Wont hurt for a short time

steve m - 28/3/15 at 08:11 AM

Yesterday runs were 99% successful as I used the old thermostat with two holes drilled
I let it idle for about half an hour the fan came on twice, but it did vent out about half a pint
however the car was not level, so the next trial will be to get it out on the road

steve

Norfolkluegojnr - 28/3/15 at 10:49 AM

quote:
Originally posted by steve m
Yesterday runs were 99% successful as I used the old thermostat with two holes drilled
I let it idle for about half an hour the fan came on twice, but it did vent out about half a pint
however the car was not level, so the next trial will be to get it out on the road

steve


Have you got it running to an expansion tank? Should help. Glad you're getting there, cross flows are a pain for cooling

Paul Turner - 28/3/15 at 01:08 PM

quote:
Originally posted by Norfolkluegojnr
cross flows are a pain for cooling


No they are not.

I ran x-flows from about 1975 to 2002 in various Fords and latterly in my Seven. Thy ranged from bog standard 1300 to a bored and stroked 1860 with 175 surprisingly tractable bhp.

None of them had a sealed cooling system The early ones just dumped any excess onto the road and then remained at a constant level in the radiator, the later ones used a simple blow and suck system.

Most had heaters, the last ones in the Seven didn't.

Always used 74 degree stats and latterly a 85 degree fan switch (early ones used the viscous fan) and all ran at a steady 78 degrees on a reliable gauge when cruising.

The only time I had issues with water being blown out excessively was when the head gasket was giving issues or in the case of one engine when the chap who had decked the block was a total arse hole and the gasket would never have sealed.

Properly built a x-flow will not have problems.

David Jenkins - 28/3/15 at 03:56 PM

Maybe this chap's advice will help - it's what I did with my x-flow:

Dave Andrews - oil and water

He's talking about a Pinto used in a Robin Hood, but the principle is identical with a x-flow.

I used an overflow tank from a Daihatsu I found in a scrap yard...

[Edited on 28/3/15 by David Jenkins]

Norfolkluegojnr - 29/3/15 at 07:38 PM

How's it going Steve? Success?