Huge cooling problems and cap query
Discussion
Just wondered if someone could answer a question for me with regards to the cooling system on a 1987 350i.
I have 2 “radiator” caps on the engine. The first one is located on the metal pipe that runs from the block to the radiator, and this has one of the pressurised caps installed (the type with a spring). The other cap is a non-pressurised type (flat blanking cap) and is located on the expansion bottle just to the lower left of the windscreen. These have been in place ever since I’ve owned the car (8 years), however the car has always been fussy with regards to its temperature. My question is, should both of these caps be of the pressurised variety, or is it correct that the expansion bottle has a non-pressurised variety?
As I say, I’ve always suffered with water being pumped out of the expansion tank whilst in traffic and when the engine gets hot. Even on normal cruising in summer, the fan will cut in and I’m always topping up the expansion bottle each time I use the car. I’ve never really been able to compare the car to another one, until now that is. My neighbour has just bought a 350SE, and he has 2 pressurised caps on his engine. Is this normal? I removed his expansion tank one today and was greeted by a hissing sound, suggesting that the system was pressurised. I don’t see how my system can be pressurised without having 2 of the springy type caps. In fact, I’ve never heard a hissing sound when removing any of my caps.
I’ve just tried to change the coolant and once again have huge problems. As soon as the engine gets to around 85-90 degrees, the expansion tank gets full, and the almost boiling coolant comes out of the overflow pipe on the top, fills the container underneath the expansion tank alarmingly quickly, and then overflows this too. The fan cuts in, but struggles to control the flow of water. In the end, I have to switch off the engine, and as it cools all the coolant in the 2 expansion tanks gets sucked back in. I then have to add loads more coolant to replace that which spilled out before trying again. After about 4 times of doing this, things seem to calm down a little, however every time the water gets hot, it gets expelled out of the expansion tank again. Its been like this for 8 years now, but perhaps this isn’t normal and I need a change of cap!
What do other people have on their car, and what happens when the car gets up to temperature? Every time mine gets hot, water comes out of the expansion tank and fills the lower container, then the fan cuts in and eventually the water cools enough to get sucked back into the engine. Surely though all this water shouldn’t keep coming out, and having 2 pressurised caps would stop this? The expansion tank neck seems to be designed to take the pressurised type cap.
Any help would be so drastically appreciated! Sorry this post is sooo long and muddily too!
I have 2 “radiator” caps on the engine. The first one is located on the metal pipe that runs from the block to the radiator, and this has one of the pressurised caps installed (the type with a spring). The other cap is a non-pressurised type (flat blanking cap) and is located on the expansion bottle just to the lower left of the windscreen. These have been in place ever since I’ve owned the car (8 years), however the car has always been fussy with regards to its temperature. My question is, should both of these caps be of the pressurised variety, or is it correct that the expansion bottle has a non-pressurised variety?
As I say, I’ve always suffered with water being pumped out of the expansion tank whilst in traffic and when the engine gets hot. Even on normal cruising in summer, the fan will cut in and I’m always topping up the expansion bottle each time I use the car. I’ve never really been able to compare the car to another one, until now that is. My neighbour has just bought a 350SE, and he has 2 pressurised caps on his engine. Is this normal? I removed his expansion tank one today and was greeted by a hissing sound, suggesting that the system was pressurised. I don’t see how my system can be pressurised without having 2 of the springy type caps. In fact, I’ve never heard a hissing sound when removing any of my caps.
I’ve just tried to change the coolant and once again have huge problems. As soon as the engine gets to around 85-90 degrees, the expansion tank gets full, and the almost boiling coolant comes out of the overflow pipe on the top, fills the container underneath the expansion tank alarmingly quickly, and then overflows this too. The fan cuts in, but struggles to control the flow of water. In the end, I have to switch off the engine, and as it cools all the coolant in the 2 expansion tanks gets sucked back in. I then have to add loads more coolant to replace that which spilled out before trying again. After about 4 times of doing this, things seem to calm down a little, however every time the water gets hot, it gets expelled out of the expansion tank again. Its been like this for 8 years now, but perhaps this isn’t normal and I need a change of cap!
What do other people have on their car, and what happens when the car gets up to temperature? Every time mine gets hot, water comes out of the expansion tank and fills the lower container, then the fan cuts in and eventually the water cools enough to get sucked back into the engine. Surely though all this water shouldn’t keep coming out, and having 2 pressurised caps would stop this? The expansion tank neck seems to be designed to take the pressurised type cap.
Any help would be so drastically appreciated! Sorry this post is sooo long and muddily too!
Daniel
don't think you are that far from me (Ipswich) and I have a selection of caps after the last very frustrating coolant change
Getting a good seal was an absolute mare on the swan neck
Let me know if you want them
Just to add
the expansion cap is sprung, the swan neck isn't
airlocks are a pain to get rid of
>> Edited by cuneus on Saturday 3rd December 18:25
don't think you are that far from me (Ipswich) and I have a selection of caps after the last very frustrating coolant change
Getting a good seal was an absolute mare on the swan neck
Let me know if you want them
Just to add
the expansion cap is sprung, the swan neck isn't
airlocks are a pain to get rid of
>> Edited by cuneus on Saturday 3rd December 18:25
My 390SE (similar caps) blew the water out of the expansion tank on one occasion when I forgot to operate the manual fan when sitting on the drive after a run.
Later I filled it, and next trip it kindly blew that out with all the new antifreeze.
I then just left the expansion tank EMPTY, rather than half full, and no blowing off since.
- Only put the fan on in traffic.
Perhaps your system needs flushing out ?
Later I filled it, and next trip it kindly blew that out with all the new antifreeze.
I then just left the expansion tank EMPTY, rather than half full, and no blowing off since.
- Only put the fan on in traffic.
Perhaps your system needs flushing out ?
On mine the spring one is on the expansion tank, so when pressure gets up it will let water into the overflow tank below it. The swan neck is a flat one only to let water circulate back to the inlet manifold at all times (I think thats where the pipe in the swan neck cap goes can remember without looking) Anyway that how they work on my 350.
Oh wow, thank you guys for the quick response! I can't wait for tomorrow now to try this out! Lol, 8 years of carrying a gallon of water around in the boot ready to do top ups, and all along the caps were the wrong way around. I'll have a go tomorrow morning and report my findings. Be great fun getting the air out of the system no doubt... Many thanks once again.
Cuneus, thank you for the offer of the spare caps. Hopefully, all I need to do is swap my 2 existing ones around. I must admit, I had a lot of trouble getting a good seal on my current swan neck cap, and in the end I cut a rubber gasget out and stuck it into the inside of the cap. I will see what happens tomorrow when I swap them, and if it looks like I need a spare I will be in touch. I too am from Ipswich by the way (well, just a few miles south actually). Have you ever been to any of the Suffolk meets? I don't seem to recall an SEAC there... Are you interested in going to any? Would be cool good to see you there to compare Wedges!
I shall report back tomorrow with my cooling results!
Dan.
Cuneus, thank you for the offer of the spare caps. Hopefully, all I need to do is swap my 2 existing ones around. I must admit, I had a lot of trouble getting a good seal on my current swan neck cap, and in the end I cut a rubber gasget out and stuck it into the inside of the cap. I will see what happens tomorrow when I swap them, and if it looks like I need a spare I will be in touch. I too am from Ipswich by the way (well, just a few miles south actually). Have you ever been to any of the Suffolk meets? I don't seem to recall an SEAC there... Are you interested in going to any? Would be cool good to see you there to compare Wedges!
I shall report back tomorrow with my cooling results!
Dan.
Hi GreenV8S,
I'm not sure if you can actually bleed the radiator seprately. On the Wedges they are quite low down in the nose cone, and almost impossible to access. The top rubber hose from the rad is joined to a metal swan neck pipe leading to the water pump, and the cap on this swan neck seems to be the highest point in the cooling system. I would have thought that if the water level is to the top of the swan neck / cap, then the rad should be full of water. There isn't any kind of bleed point on the rad, and even if one was fitted I don't think it would be accessible.
I think the worst place for an airlock on these V8 Wedges would be in the heater matrix. The pipes leading to and from it tend to bend down through the bulkhead, and then up again to the inlet/outlet towards the rear of the plenum chamber. Seems to me that air gets trapped in the matrix and cannot escape.
I will see what happens tomorrow. This will probably be the first time in many years that the system will be under preasure, so whats the betting that all the joints blow their seals! I'm already aware of one plastic T-piece that is on the edge of breaking, so I think this will be the first weak link!
>> Edited by digga951 on Saturday 3rd December 21:53
I'm not sure if you can actually bleed the radiator seprately. On the Wedges they are quite low down in the nose cone, and almost impossible to access. The top rubber hose from the rad is joined to a metal swan neck pipe leading to the water pump, and the cap on this swan neck seems to be the highest point in the cooling system. I would have thought that if the water level is to the top of the swan neck / cap, then the rad should be full of water. There isn't any kind of bleed point on the rad, and even if one was fitted I don't think it would be accessible.
I think the worst place for an airlock on these V8 Wedges would be in the heater matrix. The pipes leading to and from it tend to bend down through the bulkhead, and then up again to the inlet/outlet towards the rear of the plenum chamber. Seems to me that air gets trapped in the matrix and cannot escape.
I will see what happens tomorrow. This will probably be the first time in many years that the system will be under preasure, so whats the betting that all the joints blow their seals! I'm already aware of one plastic T-piece that is on the edge of breaking, so I think this will be the first weak link!
>> Edited by digga951 on Saturday 3rd December 21:53
digga,
I wouldn't get too excited about swopping the caps being the cure to your problem.
In a nutshell, your symptoms are exactly the same as my Wedge ('86 350i) suffers. I suspected the pressure cap on the expansion tank was to blame (spring too weak to allow the system to pressurise?), so I replaced both caps. Didn't make any difference - mine still pi55es coolant out when hot (all over the exhaust manifolds due to overflow location on my car - results in clouds of steam in traffic for great comedy value
) and I still have to top-up coolant every time I take the car out. Interestingly, if I remove the pressure cap when the engine is still warm, the resulting vacuum draws the coolant back from the overflow into the expansion tank.
My current theory is a slightly leaking headgasket causing the system to pressurise. Given the size of the bill on that, I'm happy for the car to use as much antifreeze as petrol!
I wouldn't get too excited about swopping the caps being the cure to your problem.
In a nutshell, your symptoms are exactly the same as my Wedge ('86 350i) suffers. I suspected the pressure cap on the expansion tank was to blame (spring too weak to allow the system to pressurise?), so I replaced both caps. Didn't make any difference - mine still pi55es coolant out when hot (all over the exhaust manifolds due to overflow location on my car - results in clouds of steam in traffic for great comedy value
) and I still have to top-up coolant every time I take the car out. Interestingly, if I remove the pressure cap when the engine is still warm, the resulting vacuum draws the coolant back from the overflow into the expansion tank. My current theory is a slightly leaking headgasket causing the system to pressurise. Given the size of the bill on that, I'm happy for the car to use as much antifreeze as petrol!
Buy two new caps.
Don't frig about with old ones.
Get a stone and make sure the two surfaces that the caps go onto are flat. (Or a fine file, but a stone is better)
Check the operating temp of your fan, it should be on way before you are pumping water out. Is this the original fan?, some of the aftermarket ones just don't "cut it" esp on a fibreglass car.
Are all the cowlings in place?
Even a good fan needs to on soon enough, if the car is already overheating it will not do anything. (you aready know that)
With a sealing type cap on the rad you may find that the system will bleed itself as long as the res doesn't empty during cooling.
Next step is to take it to a mech to get a pressure test. (only five minutes)
With regard to a leaky head gasket. Feel the top hose, start engine-the top hose should not become hard until the thermostat opens, if it becomes hard sooner there is a good chance the pressure you are feeling is upper cyl pressure, this along with brown frothy coolant is bad news.
While I'm typing I'll just add that flushing the heater matrix in the reverse direction often has a good effect on older cars.
Don't frig about with old ones.
Get a stone and make sure the two surfaces that the caps go onto are flat. (Or a fine file, but a stone is better)
Check the operating temp of your fan, it should be on way before you are pumping water out. Is this the original fan?, some of the aftermarket ones just don't "cut it" esp on a fibreglass car.
Are all the cowlings in place?
Even a good fan needs to on soon enough, if the car is already overheating it will not do anything. (you aready know that)
With a sealing type cap on the rad you may find that the system will bleed itself as long as the res doesn't empty during cooling.
Next step is to take it to a mech to get a pressure test. (only five minutes)
With regard to a leaky head gasket. Feel the top hose, start engine-the top hose should not become hard until the thermostat opens, if it becomes hard sooner there is a good chance the pressure you are feeling is upper cyl pressure, this along with brown frothy coolant is bad news.
While I'm typing I'll just add that flushing the heater matrix in the reverse direction often has a good effect on older cars.
I would agree with the caps on the wrong way round idea. But because of the circuit (if it is like mine) you are liable to get air locks in the system. A good palpation of the main pipe leadingf to the engine from the swan neck as you are filling and whilst you are running the engine on tick over to get the water round the system (do this before it gets hot of course!) will help.
If you do have air in the system, you are likely to use water without there being any real problem apart from that. I have heard a number of cars use water because of this - I think there was a thread about this some time ago.
However, there can be a break in the join underneath the front main cap on the swan neck. This is often difficult to spot as it will appear that the cap is leaking. If this is the case it will need re-brazing to seal the joint.
Mid Essex meet next week?
JJ
>> Edited by firefox1712 on Sunday 4th December 10:17
>> Edited by firefox1712 on Sunday 4th December 10:20
>> Edited by firefox1712 on Sunday 4th December 13:33
If you do have air in the system, you are likely to use water without there being any real problem apart from that. I have heard a number of cars use water because of this - I think there was a thread about this some time ago.
However, there can be a break in the join underneath the front main cap on the swan neck. This is often difficult to spot as it will appear that the cap is leaking. If this is the case it will need re-brazing to seal the joint.
Mid Essex meet next week?
JJ
>> Edited by firefox1712 on Sunday 4th December 10:17
>> Edited by firefox1712 on Sunday 4th December 10:20
>> Edited by firefox1712 on Sunday 4th December 13:33
one other thing to check is that the blled return to teh header tank isn't blocked as this would cause teh problems you describe. On my 350 I had to replace the header tank as the steel reinforcing pipe that sits inside the plastic one on the bleed had rusted away and was blocking off the bleed fronm the rad and inlet manifold. Ended up using an escort one in the end
Matt
Matt
The pressure cap has to be on the expansion tank as otherwise the hot coolant will blow off steam through the overflow. Similarly, if the pressure cap is fitted to the swan-neck it prevents air from bleeding off through the vent back to the expansion tank.
I suspect also that a lot of Wedge cooling issues are due to the expansion tank being so low in the first place: on my car the vent pipe from the top of the inlet manifold (theoretically the highest point) actually loops DOWN under the air intake hose: how the hell is air supposed to bleed downhill? IIRC on grahamw48's car that pipe runs across the top of the air hose in a more direct route.
My car is also onto at least its second expansion tank and this one is now leaking too.
So I'm looking into an aluminium or stainless replacement with outlets in the correct places for the shortest routing of hoses: one possibility is to mount it on the firewall just under the widscreen, that should get it as high as possible.
Initially I thought it may be possible to fit the cylindrical tank off an Esprit, but it's too tall to fit anywhere.
I suspect also that a lot of Wedge cooling issues are due to the expansion tank being so low in the first place: on my car the vent pipe from the top of the inlet manifold (theoretically the highest point) actually loops DOWN under the air intake hose: how the hell is air supposed to bleed downhill? IIRC on grahamw48's car that pipe runs across the top of the air hose in a more direct route.
My car is also onto at least its second expansion tank and this one is now leaking too.
So I'm looking into an aluminium or stainless replacement with outlets in the correct places for the shortest routing of hoses: one possibility is to mount it on the firewall just under the widscreen, that should get it as high as possible.
Initially I thought it may be possible to fit the cylindrical tank off an Esprit, but it's too tall to fit anywhere.
Hi everyone,
A big thank you to all those who posted ideas and sugestions.
I have just been out to try again with the caps swapped, and it worked! For the first time EVER, my cooling system works!!!
A brief description of what I did incase it can help others out:-
I removed both caps and swapped them over so that the springy preasurised cap went onto the expansion tank, and the flat one went on the swan neck. I started the engine and checked to see if the top hose was hard, sugesting a leaking head gasget as mentioned ealier. It wasn't so I said a quick horay, stopped the engine and removed the caps.
I topped up the swan neck with as much coolant as I could, squeezing the top hose to expell any air.
I started the engine and let it run with the caps off, topping up the swan neck with coolant constantly. I also made sure the expansion tank was at least half full at all times.
As the engine and coolant started to warm up, the level at the swan neck seemed to be full as I couldn't add anymore to the system. I squeezed the top hose until no more air bubbles appeared. Then, I also turned the heater matrix valve (just under the windscreen) off and on a few times, and this also seemed to make lots of bubbles appear. I'm guessing that most of the air was out of the system at this time, so I replaced the swan neck cap.
When the engine had got to around 80 degrees, I made sure the expansion tank was at least half full, and replaced this cap too.
As the engine heated up towards the 90 degree mark, some coolant started coming out of the overflow pipe on the expansion tank, and drained into the "catch" tank below it. By this time, the engine was at around 92 degrees and the cooling fan cut in. The coolant stopped flowing out of the expansion tank, and within about 20 seconds the engine temperature had dropped back down to around 80 degrees again. The lower "catch" tank had only filled up to just under half full.
I then let the engine warm up again, waited for the fan to cut in, and then cool down a couple more times, and it did this faultlessly! Also, when I squeezed the upper hose it was now hard from the water preasure, something that has never happened before due to caps being the wrong way around.
I swicthed off the engine, waited a few minutes and then removed the expansion tank cap. A hiss was heard, and when inspecting the coolant there didn't appear to be any froth on the surface, and the coolant was a clear blue (just changed).
So, it seems all the cooling problems from the last 8 years are now cured! I guess the real test will be when I take the car out on the roads again. I can't at the moment as it only has 3 wheels, but thats another story! I also need to replace the plastic "t" piece as I know this is very weak and the extra preasure of the system may soon make it fail.
Anyway, sorry for the long post again - just thought it would be handy to explain in detail my findings incase anyone else is having similar problems and wanted to read a possible solution. Thank you again to every one who helped!
Firefox, I'm not sure if there is a "normal" Essex meet this coming weekend or not yet. I think that next Saturday night is the Christmas meal (needed to be pre-booked), so I'm not actually sure if there will be a meet there the next day. I will email Pauline and report back to you!
Dan.
A big thank you to all those who posted ideas and sugestions.
I have just been out to try again with the caps swapped, and it worked! For the first time EVER, my cooling system works!!!
A brief description of what I did incase it can help others out:-
I removed both caps and swapped them over so that the springy preasurised cap went onto the expansion tank, and the flat one went on the swan neck. I started the engine and checked to see if the top hose was hard, sugesting a leaking head gasget as mentioned ealier. It wasn't so I said a quick horay, stopped the engine and removed the caps.
I topped up the swan neck with as much coolant as I could, squeezing the top hose to expell any air.
I started the engine and let it run with the caps off, topping up the swan neck with coolant constantly. I also made sure the expansion tank was at least half full at all times.
As the engine and coolant started to warm up, the level at the swan neck seemed to be full as I couldn't add anymore to the system. I squeezed the top hose until no more air bubbles appeared. Then, I also turned the heater matrix valve (just under the windscreen) off and on a few times, and this also seemed to make lots of bubbles appear. I'm guessing that most of the air was out of the system at this time, so I replaced the swan neck cap.
When the engine had got to around 80 degrees, I made sure the expansion tank was at least half full, and replaced this cap too.
As the engine heated up towards the 90 degree mark, some coolant started coming out of the overflow pipe on the expansion tank, and drained into the "catch" tank below it. By this time, the engine was at around 92 degrees and the cooling fan cut in. The coolant stopped flowing out of the expansion tank, and within about 20 seconds the engine temperature had dropped back down to around 80 degrees again. The lower "catch" tank had only filled up to just under half full.
I then let the engine warm up again, waited for the fan to cut in, and then cool down a couple more times, and it did this faultlessly! Also, when I squeezed the upper hose it was now hard from the water preasure, something that has never happened before due to caps being the wrong way around.
I swicthed off the engine, waited a few minutes and then removed the expansion tank cap. A hiss was heard, and when inspecting the coolant there didn't appear to be any froth on the surface, and the coolant was a clear blue (just changed).
So, it seems all the cooling problems from the last 8 years are now cured! I guess the real test will be when I take the car out on the roads again. I can't at the moment as it only has 3 wheels, but thats another story! I also need to replace the plastic "t" piece as I know this is very weak and the extra preasure of the system may soon make it fail.
Anyway, sorry for the long post again - just thought it would be handy to explain in detail my findings incase anyone else is having similar problems and wanted to read a possible solution. Thank you again to every one who helped!
Firefox, I'm not sure if there is a "normal" Essex meet this coming weekend or not yet. I think that next Saturday night is the Christmas meal (needed to be pre-booked), so I'm not actually sure if there will be a meet there the next day. I will email Pauline and report back to you!
Dan.
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