280i radiator cap pressure?
Discussion
Been having a few issues keeping the car cool, sometimes even when cruising on the freeway. New water pump, new hoses, clean rad core, new electric fan on thermoswitch.
Checked today and the overflow tank has been losing a little coolant too, so I wanted to confirm cap pressures on the V6 with the forum.
I have a cap on the expansion tank - 16 lbs. The Bible says this should be 13 lbs and my Capri 2.8 workshop manual says 12.0lb to 15.7lb (!).
However, I have a 7lb cap on the radiator itself and I'm not sure whether this is right or not...The Bible is silent on this cap.
My thinking is that once pressure exceeds 7lb the rad cap will open and send hot coolant to the expansion tank, and from there out of the bottom outlet and into the thermostat housing and back through the engine - without going though the rad!
Because there is a hose from the rad cap neck to the expansion tank it follows that there should be a sprung cap, but what should its pressure be? Closer to but not more than 13lb? Maybe they should both be 13lb?
Any thoughts guys?
Checked today and the overflow tank has been losing a little coolant too, so I wanted to confirm cap pressures on the V6 with the forum.
I have a cap on the expansion tank - 16 lbs. The Bible says this should be 13 lbs and my Capri 2.8 workshop manual says 12.0lb to 15.7lb (!).
However, I have a 7lb cap on the radiator itself and I'm not sure whether this is right or not...The Bible is silent on this cap.
My thinking is that once pressure exceeds 7lb the rad cap will open and send hot coolant to the expansion tank, and from there out of the bottom outlet and into the thermostat housing and back through the engine - without going though the rad!
Because there is a hose from the rad cap neck to the expansion tank it follows that there should be a sprung cap, but what should its pressure be? Closer to but not more than 13lb? Maybe they should both be 13lb?
Any thoughts guys?
Hi Toby
IIRC I had the same caps on the rad and expansion tank...sure it was around 14-15lb's....I should imagine they would need to be the same so that when the rad one opens so does the expansion tank allowing a flow.....I remember looking in Delilah's tank when running and there was a definite flow...Not like the V8....Which has nothing....or very little...
Ziga
IIRC I had the same caps on the rad and expansion tank...sure it was around 14-15lb's....I should imagine they would need to be the same so that when the rad one opens so does the expansion tank allowing a flow.....I remember looking in Delilah's tank when running and there was a definite flow...Not like the V8....Which has nothing....or very little...
Ziga
My car has a blanking cap on the radiator and a pressure cap on the expansion tank.
A pressure cap on the radiator would mean the system wouldn't bleed air until the pressure cap on the radiator opened, as the pressure cap on the radiator would also see pressure on the reverse side it's never going to open.
Chris.
A pressure cap on the radiator would mean the system wouldn't bleed air until the pressure cap on the radiator opened, as the pressure cap on the radiator would also see pressure on the reverse side it's never going to open.
Chris.
Thats got me thinking now Chris...
What you say makes sense...Does yours have a outlet on the rad neck going to the expansion tank?...Now I can't remember if I used a blanking cap or a pressurised on the rad...
Tried jogging my memory with some old pics...Just made me think of loads of other stuff now though...Hey ho...
Ziga
What you say makes sense...Does yours have a outlet on the rad neck going to the expansion tank?...Now I can't remember if I used a blanking cap or a pressurised on the rad...
Tried jogging my memory with some old pics...Just made me think of loads of other stuff now though...Hey ho...
Ziga
Mine had a blank cap too, so there was a permanent flow through the plastic expansion tank.
I don't think it's necessary though. The original early Granny only had the 'standard' type single cap with overflow pipe, not even going to an expansion tank.
They had a rad with a bigger (deeper) top tank, which was for water expansion. Later cars had smaller top tank (as per Wedge) and various overflow setups.
When my plastic tank cracked, I couldn't find a new one, so I changed it for a single small pipe (1/4 inch) feed from the top of the engine to an old style (BL type) copper overflow, and dropped the heater hose T pieces and rad feed, and used a 16 lb cap on rad, and 14 lb cap on overflow tank. I never had any problem with it after that, and never lost any water.
I don't think it's necessary though. The original early Granny only had the 'standard' type single cap with overflow pipe, not even going to an expansion tank.
They had a rad with a bigger (deeper) top tank, which was for water expansion. Later cars had smaller top tank (as per Wedge) and various overflow setups.
When my plastic tank cracked, I couldn't find a new one, so I changed it for a single small pipe (1/4 inch) feed from the top of the engine to an old style (BL type) copper overflow, and dropped the heater hose T pieces and rad feed, and used a 16 lb cap on rad, and 14 lb cap on overflow tank. I never had any problem with it after that, and never lost any water.
taz turbo said:
My car has a blanking cap on the radiator and a pressure cap on the expansion tank.
A pressure cap on the radiator would mean the system wouldn't bleed air until the pressure cap on the radiator opened, as the pressure cap on the radiator would also see pressure on the reverse side it's never going to open.
Chris.
Thanks for the post Chris, it's got me thinking too. Agree that there would be pressure on both sides of the seal so the rad cap won't open. A pressure cap on the radiator would mean the system wouldn't bleed air until the pressure cap on the radiator opened, as the pressure cap on the radiator would also see pressure on the reverse side it's never going to open.
Chris.
But with a blanking cap on the rad, there will be a permanent flow from the top outlet into the header tank which will bypass the rad resulting in less cooling. Is that not a problem?
Yes, there will be a permanent 'bleed' of hot water with a blank cap, but the amount is very small compared to how much goes through the main pipes (1/4 inch to 1 7/8" or something like that), so not really a big problem.
I said this in another thread here - If you look how the original Capri 2.8 was connected up, the Tee is actually in the wrong heater pipe on the wedge. If it was plumbed in on the driver (= cold start injector) side, then there would be no 'bleed' flow. As Capri tank was OE on driver side it had all 3 tank pipes effectively on the same side (= OUT) of the water pump. But I think TVR plumbed the tee wrongly with tank on other side, as otherwise the heater pipes get even more ugly and one to tee would have to cross the back of the engine ....
I said this in another thread here - If you look how the original Capri 2.8 was connected up, the Tee is actually in the wrong heater pipe on the wedge. If it was plumbed in on the driver (= cold start injector) side, then there would be no 'bleed' flow. As Capri tank was OE on driver side it had all 3 tank pipes effectively on the same side (= OUT) of the water pump. But I think TVR plumbed the tee wrongly with tank on other side, as otherwise the heater pipes get even more ugly and one to tee would have to cross the back of the engine ....
Edited by RCK974X on Sunday 17th September 08:23
Mine is piped up as in the picture of Marks old car.
Yes this setup has a permanent flow of water through the expansion bottle, but the quantity as previously said isn't all that large.
And also as previously said some 2.8 Ford installations don't have an expansion tank, not sure if that's true of the injection set ups as they need the hot water to heat the AAV and WUR, so airlocks at the high point of the engine would be less than ideal.
Regards,
Chris.
Yes this setup has a permanent flow of water through the expansion bottle, but the quantity as previously said isn't all that large.
And also as previously said some 2.8 Ford installations don't have an expansion tank, not sure if that's true of the injection set ups as they need the hot water to heat the AAV and WUR, so airlocks at the high point of the engine would be less than ideal.
Regards,
Chris.
Thanks guys. Andy, I'm gonna have to read that a few more times until it makes sense to me..
I don't need a heater here so I bypassed it completely, so no T piece between the header tank and the thermostat housing.
My hoses look like Zigs except the header tank is on the drivers side and so is the alternator. I assume you had to make some room and put the battery in the boot Zig?
I put a blanking cap on it yesterday but haven't tried it out yet apart from once around the block to check for leaks.
I don't need a heater here so I bypassed it completely, so no T piece between the header tank and the thermostat housing.
My hoses look like Zigs except the header tank is on the drivers side and so is the alternator. I assume you had to make some room and put the battery in the boot Zig?
I put a blanking cap on it yesterday but haven't tried it out yet apart from once around the block to check for leaks.
440Interceptor said:
I assume you had to make some room and put the battery in the boot Zig?
Hi mateI managed to squeeze an MX5 gel battery in there as it was the only one small enough for the tapered gap but with a high capacity...The next owner put the battery in the boot....
Cheers
Ziga
I thought it did still get cold in Perth sometimes ?
Best thing I reckon is to look at a Capri diagram for water flow. From what I said, I see from photos that some wedges *do* have the lower pipe from overflow tank connected across the back of the engine to the driver's side (cold start injector side for USA) heater hose, which will have less (or zero) flow across the O/F tank.
Mine had the pipe connected to nearest heater hose . Perhaps someone did it wrong later .... I didn't think about that !
If you drop the heater, as said above, it's best to have some flow through the aux air valve (on front of plenum) to keep it warm, so probably best to loop the pipes (I guess you will have already done that).
I chose the top of the engine for my alternate o/f tank, as it's the highest point, so any bubbles will get pushed out.
Flow -
Water pump pushes coolant out the top rad hose, and sucks in from bottom rad hose. Unusual that thermostat is in bottom.
Anything connected to top of engine, or near the top rad hose is therefore 'hot water out' and anything connected to thermostat area is 'cold in'.
There is a bypass hose from top of engine to thermostat, (behind thermostat housing) probably to make sure thermostat opens.
Inside, the main block feed hole is on cyl no 1 side, and flows out by cyl 4.
Hope that helps .....
Best thing I reckon is to look at a Capri diagram for water flow. From what I said, I see from photos that some wedges *do* have the lower pipe from overflow tank connected across the back of the engine to the driver's side (cold start injector side for USA) heater hose, which will have less (or zero) flow across the O/F tank.
Mine had the pipe connected to nearest heater hose . Perhaps someone did it wrong later .... I didn't think about that !
If you drop the heater, as said above, it's best to have some flow through the aux air valve (on front of plenum) to keep it warm, so probably best to loop the pipes (I guess you will have already done that).
I chose the top of the engine for my alternate o/f tank, as it's the highest point, so any bubbles will get pushed out.
Flow -
Water pump pushes coolant out the top rad hose, and sucks in from bottom rad hose. Unusual that thermostat is in bottom.
Anything connected to top of engine, or near the top rad hose is therefore 'hot water out' and anything connected to thermostat area is 'cold in'.
There is a bypass hose from top of engine to thermostat, (behind thermostat housing) probably to make sure thermostat opens.
Inside, the main block feed hole is on cyl no 1 side, and flows out by cyl 4.
Hope that helps .....
RCK974X said:
I agree. That's why I used a 16lb on rad (will never open) and a 14lb on the overflow tank..... the 16lb effectively seals the little overflow pipe on the rad.
Ah, the joys of re-using other manufacturer's bits in ways they weren't intended !!
That sounds familiar....Ill give the Ford guy a call....Ah, the joys of re-using other manufacturer's bits in ways they weren't intended !!
Sardonicus said:
mrzigazaga said:
Just called the Ford guy and he confirms that it should be a blanking cap on the rad and a pressurised cap on the bottle...
Thats how it was on the Ford cars fitted with the 2.8i Cologne motor e.g the Capri Gassing Station | Wedges | Top of Page | What's New | My Stuff