M30 Porous head?

Post Mon May 15, 2006 1:01 pm

Hi folks, havin a bit of a problem. I think the head on my M30 might have gone porous, after being left overnight there is always a lump of air in the thermostat housing (its higher than the header tank) If i dont bleed it off by holding the header tank up, loosening the cap and opening the bleed screw, the gauge goes into the red if the car is run for a while, stopped and then started again. It runs fine with no missfire and doesnt use any water.
Im hoping it might just be the header tank cap venting and allowing the water to level off but i think there would have to be air entering the high part of the engine for this to happen.
Any ideas before i take the head off to get it checked out?

Post Mon May 15, 2006 1:26 pm

I think the header tank should be higher than the thermostat so you dont get air locks try moving the tank.

ED

Post Mon May 15, 2006 2:01 pm

I dont think any other of the M30 boys have had this problem?

Post Mon May 15, 2006 2:39 pm

your system may not be fully bled and air is working its way round to there.

I had a frikin nightmare getting mine bled the first time had a huge lump of air in the top of the rad .

Seriously doubt there is anthing wrong with the head.

Post Mon May 15, 2006 5:28 pm

I think im gona buy a new cap and try that, ill just keep bleeding it and see what happens. Ive been running it a couple of months now tho, surely there wouldnt still be air in it?

Post Mon May 15, 2006 9:05 pm

Like said before, sounds like your header tank needs to be higher ?

Which header tank have you used in what location ?

Do you get constant hot air from your heater ?

Have you got the little arrow on the thermostat pointing upwards ?

I've never had any bother with mine, M20 header tank in the stock position.

I just hope you've not done any thing bad to the engine as it's been in the red ?

Post Tue May 16, 2006 6:55 am

Its the standard header tank in the standard location, i get hot air apart from when if the engine is run, stopped then run again and the gauge goes into the red. I did change the thermostat when i put the engine in but i would have checked the position when i fitted it. I might double check it tho!
Andy, I assume that your header tank is lower than the top of your engine? i think my engine is slightly higher than others as i have used m5 rubber mounts but there not much difference.

I might need that spare head you`ll be selling!

Post Tue May 16, 2006 7:55 pm

I'd try to take a better picture but it's in bits at the mo

If you need the head i'll save it for you but it just sound like unbled air thats not getting out,is there some way you can temp' raise the header tank ?

May be you could try the M30 E34/2 header tank mounted on the bulkhead like Toby's ?

Post Wed May 17, 2006 6:57 am

Im going to get some original 325 mounts and try it then. Its awkward that it only seems to happen over period of time so i willl have to leave it for a few days after trying each thing to see if its made a difference. I started it last nite and there was no missfire or steam so hopefully head is ok. I think your engine does look a bit lower than mine andy, i thought about mounting the e34 header tank but there is quite a bit of wiring in the way.

Post Wed May 17, 2006 3:02 pm

here is a pic of mine.

Post Wed May 17, 2006 4:35 pm

Ritchie wrote:Im going to get some original 325 mounts and try it then. Its awkward that it only seems to happen over period of time so i willl have to leave it for a few days after trying each thing to see if its made a difference. I started it last nite and there was no missfire or steam so hopefully head is ok. I think your engine does look a bit lower than mine andy, i thought about mounting the e34 header tank but there is quite a bit of wiring in the way.

I never thought about lowering the engine

If possible can you take a picture of the M5/M20 mounts side by side for me please ? It would be nice to see how much they differ.

Sounds like you head is OK touch wood

Ed, looking good mate, love the black painted look and the almost stock look of the engine bay with the M30 air box, i've had one of those bulk head wiring covers for ages but i've not got around to fitting it

Have you got much left to do ?

Post Wed May 17, 2006 4:51 pm

Ritchie

if you've bled it thoroughly by holding the header tank as high as possible against its rubber hose, then opened the bleed screw and revved it idled it and generally got a lot of coolant through the system, there should not be air in there and it certainly shouldn't need bleeding again.

as far as i can see, header tank height should only be an issue while bleeding the system initially

maybe exhaust gas getting in to system from HG/corroded head.

Ed. that looks brilliant

Post Wed May 17, 2006 6:03 pm

Thanks, just got to plumb it up and fill it with water, going to sort he body work out as well.
ED

Post Wed May 17, 2006 9:03 pm

Looks good Ed

Andrew

Post Thu May 18, 2006 6:55 am

Andy335Touring wrote:
Ritchie wrote:Im going to get some original 325 mounts and try it then. Its awkward that it only seems to happen over period of time so i willl have to leave it for a few days after trying each thing to see if its made a difference. I started it last nite and there was no missfire or steam so hopefully head is ok. I think your engine does look a bit lower than mine andy, i thought about mounting the e34 header tank but there is quite a bit of wiring in the way.
I never thought about lowering the engine

If possible can you take a picture of the M5/M20 mounts side by side for me please ? It would be nice to see how much they differ.

Sounds like you head is OK touch wood

Ed, looking good mate, love the black painted look and the almost stock look of the engine bay with the M30 air box, i've had one of those bulk head wiring covers for ages but i've not got around to fitting it

Have you got much left to do ?

Sorry Andy, i cant get a photo of the M5 mounts but from memory there about 3/4" higher than the originals.

Post Thu May 18, 2006 7:02 am

Toby_Unna wrote:Ritchie

if you've bled it thoroughly by holding the header tank as high as possible against its rubber hose, then opened the bleed screw and revved it idled it and generally got a lot of coolant through the system, there should not be air in there and it certainly shouldn't need bleeding again.

as far as i can see, header tank height should only be an issue while bleeding the system initially

maybe exhaust gas getting in to system from HG/corroded head.

Ed. that looks brilliant

I think that the air from the top of the coolant tank is maybe travelling along the bleed hose, into the top of the rad then along the top hose into the top of the engine, what do you think Toby?
Also my top ignition lead on the distributor cap just touches the bonnet so i dont think i would have room for the cap cover like you guys have so im thinking that mine must be quite a bit higher.

Post Thu May 18, 2006 7:34 pm

I have just found this on that german site.

There needs to be 1.5-2 cm height difference from the top of the thermostat to the top of the radiator. Put another way, the output hose of the of the overflow tank must be higher than the thermostat.

For proper flow the overflow tank must be mounted as high as possible, or air will remain in the system.

I had a lot of problems with air in the system, even though I bled the system properly. Again after a week there would be air in the system and the bubble would go to the thermostat. This posed a great problem as the thermostat would read the engine as hot, but not open and thus not use the radiator. Finally I came to understand the importance of the height of these components and got it under control.

Ever since these were remedied I have had no problems with bursting hoses or overheating!

ED

Post Mon May 22, 2006 6:51 am

Right, this weekend i changed the mounts the engine is sitting a bit lower now so ill give it a try and report back!
The only thing now is the sump is resting on the steering rack and vibrating like a bstard

Its never ending! im gona have to take the grinder to the top of the rack now.

Post Mon May 22, 2006 8:07 am

shim it up a bit, shouldn't need to be that low

mine was like that when first built, horrible!

have been away for the wknd, sorry i didn't reply before mate.

the drain from the reservoir is at the bottom, as long as the drain is higher than the thermostat/rad top etc, and the tank's got lots of coolant in, air shouldn't be able to get back to the engine once bled.

however you NEED to bleed it with the tank high up.

Post Mon May 22, 2006 12:43 pm

Aye, ill half to shim it up a bit. There is no way i can get my drain from the header tank higher than the thermostat without using the 5series header. Your header is in the standard location toby, yeah? i dont see how yours can be higher than your thermostat, although its difficult to judge heights from a photo.

Post Tue May 23, 2006 6:52 am

Right then, i made up shims yesterday and fitted them last night. Hopefully this will help, ill post again when i make any progress. Thanks for the advice folks.

Post Sat May 27, 2006 6:57 am

It looks like i might still have a problem, Ive used the car a few times this week and every time before ive sterted it ive lifted the header tank and opened the bleed screw and im still getting air out. I runs fine after this but i cant live with bleeding it every time i use it!
It looks like i will have to think about re-locating the header tank. I dont see how nobody else has this problem, just my luck!

Post Sat May 27, 2006 1:38 pm

I don't know if you've tried it but make sure the little pipe that go's from the top of your rad to the expantion tank isn't blocked ?

Post Mon May 29, 2006 1:05 pm

Ive tried that andy, you can see the water squirting out when the engine is running.
I did about 100miles with it at the weekend, i bled it before i started it and got a little air out. I will try and bleed it tonight and see if i still get air out of it. I think the amounts of air may be getting smaller which is a good sign!

Post Mon Jun 12, 2006 3:13 pm

Update! still getting air and the other night it was running for ages and i stopped it for ten minutes, when i started it again there was a bit of steam from the exhaust so im sure the head is the problem. Still, at least it give me a chance to do a bit of gasflowing and fit a new cam with another head.