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Post by cyf on Jun 22, 2015 17:55:11 GMT
Hi Everyone
I began my new job nearly two months ago,so I feel more at ease now, I passed my exam last week, so the evening and week end homeworks are gone, I can go back to play in the garage!! At last!
So yesterday I worked on our neglected P5 (it didn't move sinve October)in order to drive it and prepare it for the National: I replaced the rear shock absorbers and the radiator (you may recall that it has a hole since the last National). Everything went fine but I don't see the coolant coming from the inlet manifold to the radiator. Well, in fact I saw some spit of coolant but that's all. No overheat.
I guess it's a problem of air trapped somewhere. How can I do to make the coolant find it's way t the radiator?
Happy to be back
Thank you
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Post by guidedog on Jun 22, 2015 18:41:06 GMT
Welcome back Cyf, glad your new job is going well.
The manifold normally vents on its own, the rad is higher than the manifold.
If you are unsure remove the pipe from the radiator and blow through it the air will go to manifold then back to rad.
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Post by petervdvelde on Jun 22, 2015 18:42:39 GMT
Good to see you back. There is a small hose running from the radiator to the top of the manifold. The small pipe on the manifold where the hose is attached is often blocked and that could cause an air lock. With a small drill you may be able to free it again. I would not worry too much as when the engine is cold, the thermostat is closed and no coolant can get past except along the small hole for the pin. Just connect the 2 big hoses to the radiator, then fill up the radiator with coolant, set the heater on hot and let the engine run until the thermostat opens. Afterwards check the coolant level again.
Peter
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Post by cyf on Jun 22, 2015 20:05:04 GMT
Thank you for the answers. I refilled with coolant let the engine run, everything was fine but no return from the inlet manifold pipe. Before i changed the radiator -this means months ago- there was a flow. I probed the small pipe on the manifold and it was not blocked.
I read somewhere on the forum once (i can't remember where) that this is important to have coolant flowing from this pipe, but I can't remember why. Hence my question
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Post by johnwp5bcoupe on Jun 22, 2015 20:35:09 GMT
HELLLOOO Cyf good to hear from you  Are you saying there is no flow from the Thermostat Housing? even when hot? |
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Post by cyf on Jun 22, 2015 20:40:52 GMT
HELLOOO John!
Well no, it's from the pipe at the front of the inlet manifold to the radiator, below the filling cap at the rear
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Post by Phil Nottingham on Jun 22, 2015 21:40:37 GMT
Must be the small pipe on the manifold bridge as Peter says probe with a small drill - try probing with the engine running but block off tube to rad
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Post by enigmas on Jun 22, 2015 22:08:59 GMT
Hi Cyf, congratulations on passing your exams and the new job.  With regard to the no coolant flow which seems quite odd and can only be put down to an airlock at a high point in the manifold. If you can attach a garden hose at a point where the heater hoses connect, remove the radiator cap (or perhaps a hose at a high point) and pressurize the system you may be able to purge the air. Interesting I recently rebuilt the LPG convertor on my car which necessitated the removal of coolant lines near to the heater core. I usually bleed the system carefully but noted that the heater was quite ineffective during a recent trip. Thinking about it consulted the WSM and noted a comment stating that the heater cannot be properly drained. By virtue of this, it's also possible to have an air lock in the heater matrix, hence the lack of heat from the core. So perhaps pressurizing the system with a hose (and having an opposing outlet point) will purge the air and fix the problem. |
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Post by Warwick on Jun 23, 2015 3:37:36 GMT
Welcome back, Cyf.
Have you tried running the engine up to temperature with the hose disconnected from the radiator, the connection on the radiator plugged, and the radiator cap fitted? That would mean that as the coolant warmed up and expanded, the only way is would be through that bleed point on the manifold. That would shift any airlock in the manifold and if it still didn't flow there must be some sort of strange obstruction behind the bleed point.
If you did try this it might be best to use a long piece of hose and put the end in a bucket. That way you wouldn't waste coolant and if a blockage suddenly cleared, you can avoid being sprayed with hot coolant.
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Post by johnwp5bcoupe on Jun 23, 2015 4:31:32 GMT
HELLOOO John! Well no, it's from the pipe at the front of the inlet manifold to the radiator, below the filling cap at the rear I was just making sure Cyf just in case something was misunderstood in translation  Great news on your situation! |
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Post by cyf on Jun 23, 2015 6:50:21 GMT
Thank you everyone
Phil, I probed the pipe and it was not blocked.
Enigmas and Warwick, that's good ideas. I'll try the easiest one for me.
Can you tell me what is this hose for? It drains the coolant from the manifold to the rad but why? Is it a big issue if there's no flow?
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Post by Warwick on Jun 23, 2015 7:57:15 GMT
The top of the manifold is a high point, Cyf, so air would become trapped there. The small nipple near the top, and the hose connected to it, allows any air to escape into the top of the radiator and from there into the expansion tank. It also would allow a small flow of coolant to keep moving out of the top of the manifold to stop stagnant pockets developing, causing localized hotspots. But the air bleeding issue would be the main reason.
A very sensible solution to the problem. Don't ask me what I think about the methods used on my 406.
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Post by enigmas on Jun 23, 2015 9:00:31 GMT
Air pockets anywhere in the cooling system are bad as the trapped air can cause a range of issues that are detrimental to efficient cooling. Steam pockets can occur with consequent over pressurization and purging. This can often be both felt and heard in the top hose. Conversally an air pocket in a heater core will inhibit heat transfer, although the engine may be up to temperature. Cyl wall hot spots and consequent bore distortion can also occur if air pockets are trapped beside a cyl. This causes localized expansion at that point, causing bore distortion and a high probability of a piston ring grabbing the cyl with consequent damage. (Though this is only likely to occur in a silted up block.) Air caught at the rear of cyl heads will cause steam pockets, leading to over pressurization and constant purging issues. More so in modified cars with engines setup completely level rather than slightly higher at the front.
I don't think you need to concern yourself with the worst case scenarios though Cyf!
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Post by cyf on Jun 23, 2015 9:49:28 GMT
I hope so Enigmas!
OK it's an escape for the air of the manifold then. As I always saw coolant coming from this pipe I was worried to see nothing. I don't want to leave it like that, I'll try to drain the air and see the coolant flowing again
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Post by enigmas on Jun 23, 2015 11:36:51 GMT
Cyf my SD1 Rover V8 powered MG Magnette utilizes twin Stromberg CD carbs and has the same small bleed tube for the manifold under the PS carb (right hand drive car, like in the UK.) It was similarly blocked, so I used an electric cordless drill and an 1/8" bit. Job done! The auto choke heat capsule on the carburettor on the right hand side of the picture below, is fed hot coolant from that bleed tube in the manifold. If it were blocked the choke would not be able to respond to engine temperature and the engine would continue running on full enrichment until it stalled.  |
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Post by cyf on Jun 23, 2015 12:28:28 GMT
Interesting. When I probe the nipple, it goes straight , no block.
Seing the Stromberg carbs makes me think that I didn't told you something: in November I bought a '81 Range Rover with this type of carbs. I rescued it from being prepared for serious off road. There's job to be done but not that much to put it on the road, but quite a lot to bring it back to his former glory.
I'm desperatly looking for a pair of front seats with built in safety belt
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Post by cyf on Jun 24, 2015 20:08:56 GMT
Everything's fine: I did what Warwick suggested and the coolant now flow from the manifold. I'm very pleased of that
I'll take the car to go to work tomorrow
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Post by lagain on Jun 24, 2015 21:01:12 GMT
I have an expansion bottle fitted on my car, from of all things an Allegro !
When I change the coolant I tie the bottle up on the open bonnet catch. With the radiator supposedly full I replace the cap on the rad and start her. I then keep topping up the expansion bottle and it is amazing how much more I can get in.
It solved all the air lock problems
If you are accelorating up a hill and you can hear a gurgling noise that is air in the system
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Post by Simon H on Jun 24, 2015 22:35:40 GMT
I have an expansion bottle fitted on my car, from of all things an Allegro ! When I change the coolant I tie the bottle up on the open bonnet catch. With the radiator supposedly full I replace the cap on the rad and start her. I then keep topping up the expansion bottle and it is amazing how much more I can get in. It solved all the air lock problems If you are accelorating up a hill and you can hear a gurgling noise that is air in the system How have you plumbed in the expansion bottle? |
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Post by cyf on Jun 25, 2015 15:19:12 GMT
Do you use the overflow pipe?
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Post by petervdvelde on Jun 25, 2015 16:12:19 GMT
I believe it is best to make a "T" connection in the hose which is running from the manifold to the radiator. You cannot use the overflow connection as this functions like a "one way" valve and will on;y let water or air out of the system.
My MGB with Rover V8 has an expansion tank and this is connected to a small pipe rather on top of the radiator but not "after" the cap like the overflow connection.
Peter
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Post by cyf on Jun 25, 2015 19:30:49 GMT
You're obviously right Peter. I did'nt think enough before I post.  |
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Post by enigmas on Jun 25, 2015 22:12:40 GMT
You'll also need the correct type of radiator cap Cyf. If you're creating a recovery system you'll need a cap with a small return valve at centre.
Peter Without a return valve that senses vacuum how do you make a recovery system operate?
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Post by petervdvelde on Jun 26, 2015 13:15:48 GMT
On my MGB V8 there is no cap with a center valve. I believe the expansion tank's function is that the radiator can be filled 100% with coolant. In a cooling system there needs to be a bit of air to accept volume changes caused by temperature differences. With the P5B the radiator cannot be filled up 100% and the radiator functions therefore as an expansion tank.
I doubt that adding an expansion tank will help. There are lots of P5B's driving around without this extra tank, including my daily. I don't have any problems with overheating and this makes me believe that the standard cooling system is cooping with the heat produced by the standard V8. If you have overheating issue's, the cause will be likely a tired engine, lean mixture or a partly blocked radiator.
If a highly tuned engine has been fitted, then a standard cooling system could be insufficient.
If you fit an expansion tank, make sure the level in the tank is higher then the top of the radiator, otherwise it makes no sense
Peter
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Post by Steve P5b on Jun 26, 2015 14:09:01 GMT
Hi Peter that's interesting information you have but not actually 100% correct in that an expansion tank can be lower than the top of the radiator. A normal pressurising cap is fitted to the radiator and the system filled to the brim. On expansion coolant moves through the cap and out through an overflow hose with the other end effectively dangling into a reservoir ( expansion tank open to atmosphere ) below the level of water inside. as the coolant cools it reduces in volume and the displaced coolant returns through the standard pressurised cap. This works as long as there is no air present.
It does have it's faults in that many people look and check the level in the expansion tank thinking coolant is present, however it's possible the coolant level in the system is very low due to many reasons ( leaks etc.) creating a possible overheating situation.
Personally the system you describe with a see through expansion vessel works the most effectively and also signifies the coolant level without opening the system as required in our p5b's.
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With regard to the no coolant flow which seems quite odd and can only be put down to an airlock at a high point in the manifold. If you can attach a garden hose at a point where the heater hoses connect, remove the radiator cap (or perhaps a hose at a high point) and pressurize the system you may be able to purge the air. Interesting I recently rebuilt the LPG convertor on my car which necessitated the removal of coolant lines near to the heater core. I usually bleed the system carefully but noted that the heater was quite ineffective during a recent trip. Thinking about it consulted the WSM and noted a comment stating that the heater cannot be properly drained. By virtue of this, it's also possible to have an air lock in the heater matrix, hence the lack of heat from the core. So perhaps pressurizing the system with a hose (and having an opposing outlet point) will purge the air and fix the problem. 
