E34 Collant Issue

[machinehead]

I have recently got a 525i E34, FSH, auto. I asked that the radiator should be changed as the one in the car had a small leak (more of a weep), and it is an after market one I’ll admit, but bear with me. The odd thing is that after the car has been run and allowed to cool, say over night, the expansion tank is empty of water (and causes “Low Coolant Level” warning). If I then remove the radiator cap then water returns to the expansion tank and the level is quiet ok.

What I don’t understand is why the water does not flow back by itself, and to where it goes, and where has the air come from? There is always pressure when the cap is removed even after >1day without use, like after this weekend, parked if Friday night, still pressure this (Sunday) pm.

The fan is fine (I had it clutch changed, poss waste....), water pump changed about 8,000 miles ago, stat changed at same time (have receipts). temp runs dead on 1/2 even after the biggest caning I can give it!! (in fear on incrimination I wont say where/when/how much!). Before the fan-clutch change it would get over 1/2 but had to be in stationary traffic for 5->10 mins but I've not be caught in any traffic queues since so not absolutely sure that this is fixed. I searched the forum here for hours this weekend trying to piece together an answer but without success.

Can anyone give me ideas? Was thinking of getting compression test done in case head gasket gone, however there is no oil in the water, nor water in oil (I asked about this when it was serviced 4 weeks ago). No steaming except when cold, but they all do that.

Regards, Nigel.

BeelZibub, still not got those Lira

[billB]

Machinehead: You said A.If I then remove the radiator cap then water returns to the expansion tank and B. theThere is always pressure when the cap is removed even after >1day without use, like after this weekend, parked if Friday night, still pressure this (Sunday) pm. level is quiet ok.
Doesn't that tell you; you have a problem with your CAP once removed the coolant flow back she keeps it in does not want to let go of your coolant!!!

Regards
billb

[Furious]

well, a few things here ....... first one is did you get the system bled right? chances are who ever did your change forgot or didnt know how to bleed the system right. it willl cause air pockets in the system which will in turn cause symptoms such like yours and could cause a few suprises if you dont get it fixed soon.

secondly is , if you bled the system right, are you sure you were getting a good suficiant flow of coolant back from return hose? you could have a blockage in the the system. now normally what i would do is start the car (when its cold or cool) and open the rad cap, now check to see if you are getting a decent amount of coolant comming back into the expansion tank. (should be like a weak stream that will shoot downwards and hit the opposite wall close to near the upper middle of the bottle. if its trickling or dripping or none at all, you have a blockage in the system somehwere.


cooling systems are actually trickier than they seem and cause headaches for all mechanics. trust me ive seen too many hair pullers.

[billB]

Furious
If his system was not bled properly the car will overheat!

[Furious]

not all the time. ive seen cars come into my mechanic shop that were done at joe-corner-garage and the system wasnt bled properly, they never had overheat problems its odd. i know , but i suppose it does happen. also ive read a few posts on these forums about this same issue and they never mention a problem with an overheat just that there is no coolant in the expansion tank.

[billB]

Sounds good to me thanks for the quick reply
regards
billb

[Furious]

lol, like i said cooling system problems are a headache, when i did my whole system , i was aggrivated to the bitter end.

[machinehead]

Thanks for the swift replies

Furious, you say about the flow - my rad has the expansion tank on the LH side of the rad, and a small tube that feebs back to the neck of where the rad-cap screws in, having just had a look in my lunch break, will check the flow thing but as its a new rad I can't see this being blocked but it is so high in the neck that it must have to flow past/through the cap itself, which sits quite deep.

Re bleeding, a reputable garage bled it out, 2 friends have used the same garage over the past 7 or 8 years no probs, all mechanics are ex-BMW, although I accept this is no guarantee. I've cracked open the rad bleed screw and only coolant comes out. I’ve read many posts about bleeding but none seem to be along the same lines as the problem mine has

I'll try a new rad-cap (per Billb) at £7.99 and see if this might cure it...............

thanks
Nigel

[billB]

Furious

Looks like I won the battle of machinehead; But don't worry you did NOT loose the war. See you in the next round of troubleshooting.
regards
billb

[Furious]

Originally posted by billB@Nov 1 2004, 07:30 PM
Furious

Looks like I won the battle of machinehead; But don't worry you did NOT loose the war. See you in the next round of troubleshooting.
regards
billb

[snapback]222561[/snapback]

the good thing is that we all win, because we disscuss previous accounts with problems we have encountered , and others who havent experienced them yet win more than us. its always hard to diagnose a problem over the internet, the fact that we can get some of the issues right is amazing enough. and we continue to learn.

[Furious]

p.s- you can win these as long as i dont lose too many of the e36 ones.. hehehe

[billB]

With all kidding aside the ultimate goal is to help/communicate in a sincere and respected manner
regards
billb

[machinehead]

Well I've appreciated all the help guys, & only hope the new cap (didn't arrive in the post today, no surprise there) is the easy, cheap solution.

Anyhow, I removed the cap and ran the engine and there is a nice flow from
the little pipe at the top of the expansion tank neck. With the cap in place then this hole seems to be covered up and I wonder whether this is part of the problem.

I've tried to find and exploded view of the cap as it is not a simple sort of rad cap, & I assume its in more than one part (although its one piece). there is the flat rubber seal at the top, an O ring part way down, and a further O ring near the base. The pipe mentioned above seems to feed in between the lower and middle O
rings and there appears to be a small hole in this section of the cap which I guess
lets the water back into the expansion tank. Is there some sort of one-way
valve in this?

I wish there was some way of seeing it in diagram form, you know? My Honda has all fiches available online but cannot find this detail for the BM, yet.......... the parts book is not detailed enough as all the components are split apart, great to see what's what some of the time, and find part number, etc...

When cap arrives I'll post an update

Kind regards
Nigel.

[billB]

Some other dealer may have it in stock!!!
Good luck

[machinehead]

Ok, the new fan clutch has cured the overheating issue

After proving this to be the case I changed the cap for a new one....

I'm still getting air in the expansion tank. Its like when the car is turned off and cools the water level doesn’t balance out and find its natural, even, level as the air in the tank is not escaping, nor is it feeding back through the little pipe in the neck of the filler (which is not blocked, see posts above).

Again there is no loss of water as removing the cap when cold allows the level to balance at the cold mark. I have checked the level daily for nearly a week now over a distance of about 500 miles.

Any one got any further thoughts?

I can only think that the aftermarket radiator doesn’t have the tube in the right place and is obscured by the cap. Either that, or the head gaskets is going (gone) and blowing a small amount of gas into the cooling system, but not allowing water into the cylinders?