E30 Zone

Hi Zoners,

I have a cooling system query / question for you.

I thought I had a small coolant leak so I thought I'd use Radweld as a temporary fix. I then read that the M20 engine doesn't like it. So I've flushed the system by doing the following:

1. Drained coolant
2. Put in a coolant flush & toped up. Ran for approx. 10 - 15 minutes
3. Drained coolant.
4. Flushed all using a garden hose (including flushing through the heater matrix hoses (Note: matrix is linked out as there is a hole in it - another job I need to get to)
5. Refilled with fresh coolant
6. Bleed coolant a number of time by:
a. Opening the bleed nipple
b. Squeezing the hoses
c. Having the car on a slope nose up
d. Removing expansion bottle cap, putting hand over the hole and blowing down the overflow/pressure relief hose

The issues I'm having:
1. Coolant coming out the expansion bottle overflow/pressure relief hose. Though I may have over filled but was ok.
2. When warm the rubber hoses get pressurised but it feels like air inside rather than water when I squeeze them.
3. When left overnight and before starting there is still pressure in the system when I take the expansion bottle cap off.
4. Today when ticking over the temperature gauge went up to 3/4's before I turned the car off. Gauge never used to go past 1/2. When I feel the hoses from the thermostat housing the one going to the top of the radiator is very hot. The one going to the block is warm/hot (but not as hot as the one to the top of the rad). The one from the bottom of the rad is cold.

I'm hoping it not the head gasket that is gone and pressurising the system (I don't have a test kit to do a sniff test but there is no oil in the coolant and there is no white gunk when I take the oil cap off). So I was think on checking the following first but what are your thoughts before I start:

1. Remove thermostat and check it is opening (might just replace anyway). Could be the reason for overheating. Note: I didn't remove the thermostat when doing the flushes so it may be full of crap.
2. Water pump isn't working to circulate the coolant.
3. Head gasket (hopefully not) - Might see if I can get the local garage to do the sniff test.

Thanks.

Good shout on flushing because that RadWeld stuff is pure gunky shite. First question would be do you have hot air from heaters? Did you have heating on full when bleeding?

Annoying as it may be I think you may still have an airlock. After the engine is warmed up (spirited drive) the lower hose to rad should be really hot, and you should have hot air blasting from air vents.

You absolutely should change the thermostat as well as it is so easy on 325i end they cause all sorts of problems. Three bolts on thermostat housing abs pop a new one in. I bought one from GSF £5 and works perfectly. Being a 325i your temp needle should be at 1/4

Thanks BristolE30.

Before this started the temperature would run just below half.

The heater matrix is linked out (two rubber hoses are linked together) as there is a hole in it. I did make sure the two hoses were as full as possible before joining them back together.

It might be my imagination but the engine also sounds like it is making a louder ticking noise than it was before. Just wondering if that could be the bearing in the water pump and the small leak I thought I had was from it.

I'll replace the thermostat and take it from there.

Check that the small pipe from the radiator to the coolant bottle isn't blocked.
Be very careful running this engine until it's sorted. The 325 M20 head doesn't take kindly to local overheating.

Hi Brian,

Small pipe from rad to coolant bottle is clear. I checked that when I did the flush. When I squeeze the hose that goes to the top of the rad with the cap off the coolant bottle water comes out the small pipe.

New thermostat ordered and will arrive later in then week. When fitted and the system bleed again I'll report back.

Update 14/02:

New thermostat arrived Friday. Fitted it Friday afternoon, topped up the coolant and bleed the system. Ticking over temperature went up to about 3/4. Bleed again and temperature stayed at about 1/2.

Saturday morning there was pressure on the expansion bottle. As I took the lid off the expansion bottle there was coolant coming out the over flow / over pressure small hose. Bleed again. On tick over temperature was between 1/4 and 1/2 (closer to 1/2). Thought was OK.

This morning felt like there was still pressure in the hoses again. Didn't bleed this time. Ticking over for approx. 15 minutes temperature reached between 1/4 and 1/2 and was looking OK. Couple of minutes later and temperature was at 3/4 so I turned it off. Hose from thermostat body to engine was hot. Hose from thermostat body to top of rad was hot. Hose from bottom of Rad back to thermostat was cold.

I haven't been able to take the car for a run since fitting the new stat (due to weather) so I don't know what like it is on the road.

Is it normal for there still to be pressure in the expansion bottle / hoses? I don't remember it doing this before.

Do I just need to keep bleeding the system or does it sound like either the coolant pump is on the way out or could there be an issue with the head / head gasket (hope not - no oil in the expansion bottle and no sign of white gunk when taking off the oil filler cap).

Thanks.

MunsterScot wrote: ↑

Sun Feb 14, 2021 12:18 pm

Update 14/02:

New thermostat arrived Friday. Fitted it Friday afternoon, topped up the coolant and bleed the system. Ticking over temperature went up to about 3/4. Bleed again and temperature stayed at about 1/2.

Saturday morning there was pressure on the expansion bottle. As I took the lid off the expansion bottle there was coolant coming out the over flow / over pressure small hose. Bleed again. On tick over temperature was between 1/4 and 1/2 (closer to 1/2). Thought was OK.

This morning felt like there was still pressure in the hoses again. Didn't bleed this time. Ticking over for approx. 15 minutes temperature reached between 1/4 and 1/2 and was looking OK. Couple of minutes later and temperature was at 3/4 so I turned it off. Hose from thermostat body to engine was hot. Hose from thermostat body to top of rad was hot. Hose from bottom of Rad back to thermostat was cold.

I haven't been able to take the car for a run since fitting the new stat (due to weather) so I don't know what like it is on the road.

Is it normal for there still to be pressure in the expansion bottle / hoses? I don't remember it doing this before.

Do I just need to keep bleeding the system or does it sound like either the coolant pump is on the way out or could there be an issue with the head / head gasket (hope not - no oil in the expansion bottle and no sign of white gunk when taking off the oil filler cap).

Thanks.

Does sound like it’s still not bled properly. You could take it to a garage and get them to vacuum bleed it, or by the kit yourself if you have an air compressor. Then you will know without a doubt it is bled and can move on to other potential issues.

It’s weird it’s still pressurised the next day, but that does make me think it’s extra air in the system, as usually heat is what pressurises the system

So yesterday I jacked up the front of the car and put it on axle stands. Removed the expansion bottle cap then did the following:
1. Squeezed the rubber hoses till no more air bubbles coming up in the expansion tank
2. Removed the small hose from the top of the radiator (the one that goes to the top of the expansion bottle). Connected on a pressure spray bottle with coolant in it. Opened the bleed screw and used the pressure bottle to force coolant out the bleed screw. Closed bleed screw. Used pressure bottle to continue filling system till expansion bottle an correct level. Removed pressure bottle and re-connected small hose.
3. Few more squeezes of hoses.
4. Started car and let it tick over. Opened the bleed screw every couple of minutes to 10 minutes.
5. Left to idle for another 10 minutes and temperature never went above half on temperature gauge and all top hoses warm/hot.

Fixed I thought.

This evening:
Pressure still in hoses. Slowly opened expansion bottle and coolant came out the small over flow to start with and then some out the top when cap off (could be system overfilled with car being on axle stands?). Squeezing the hoses bubbles coming up from bottom of expansion bottle. With expansion cap off started car and let it tick over. Squeezing hoses no bubbles. Small bubbles seen coming out small hose from top of rad to expansion bottle so system is 'self bleeding'.

Opened the bleed screw a few times and just coolant coming out.

Coolant level rising in expansion bottle so replaced cap but not a tight as usual. Coolant coming out over flow/pressure hose. Tightened cap till stopped (still not as tight as before). Left to tick over for about another 10 minutes and never went above half on temperature gauge.

Questions:
1. Why still pressure in the system this evening before starting to do any checks?
2. Where has air came from when squeezing the hoses this evening just after taking cap off?
3. Could the pressure remaining in the system be related to the expansion bottle cap?

I'll check it again tomorrow and see how it is.

Maybe I just need to take the car for a good run.

Try Changing the matrix.
I would also get new cap and temp sensor as they are not much

I’ve had various coolant problems recently.
I also used some sealing stuff (unwisely) and took me along Time before I was getting heat out the blower. 4 or 5 flushes.

Thanks linke30.

Heater matrix is linked out as there is a hole in it (another job I need to get to).

Temperature sensor is just approx. 18 months old as I replaced the blue and brown sensors at the same time. I'll look into a new cap. Also wondering if the pump may be on the way out.

The saga continues.

After bleeding with the car on axle stands I took the car for a run today. All was going well. Came up to temperature and held at 1/4 for a bit. After about 10 minutes gauge started to rise and got to about 3/4 so shut off. When I checked coolant had been coming out the expansion bottle overflow. Hose form stat housing to top of rad = V. Hot, Hose from stat housing to pump = hot (not as hot as the one to the rad).

Eventually limped home.

Coolant light is now on so I have lost coolant.

I've ordered a new expansion bottle cap just in case the old one (it was on the car when I got it a couple of year) is knackered and not holding enough pressure.

Other thoughts I have are:

1. Head / head gasket but as mentioned above no white gunk on the oil filler cap or sign of oil in the coolant. Might just get the local garage to do a compression test & sniff test anyway.
2. Coolant pump on the way out.
3. Viscous fan coupling failing.

Any other thoughts out there?

A head gasket leak (or cracked head) directly from the combustion chamber to the water jacket won't put oil in the coolant, but you might just see a difference in the colour of the spark plug tip in the affected cylinder.
Fan coupling only affects driving in heavy traffic, and water pump would make the coolant boil violently, rather than be just pushed out.

Thanks Brian.

Any ideas what else to check? Would the best starting place be to get the local garage to do a compression test & sniff test to rule out the head & gasket before looking at changing anything else?

Check the plugs first. If gasses are leaking out, then there's a good chance that a little coolant leaks in when the engine is stopped, and this will steam clean the plug when next started.
Sniffer in the coolant bottle neck would confirm.
The cresent shaped appertures in the head can corrode under the head gasket fire rings causing this problem, but a skim usually puts it right.

Well the saga continues.

I took the car to a local garage who said it was a blocked radiator causing the overheating. New rad and water pump fitted and car was running fine. Flushed the coolant again. Took the car for a couple of runs and it was running fine. Not overheating, temperature gauge sitting between 1/4 and 1/2. Fixed I thought.

I went out the other day and the car wouldn't start. Was if the starter wasn't kicking in / was jammed. So I gate it a couple of hits with a piece of wood. Tried again and eventually it started. Well sort of. Engine making a horrible noise. Stopped the car and checked the coolant bottle and it was empty. Looks like the coolant had leaked into the engine over a couple of days and the issue was it was water locked and not the starter being the issue.

The question now is: Is it just the head gasket that will need replaced. Or, could it be a full head rebuild or even a total engine rebuild.

I haven't started to look at it yet but there is a load of oil / water leaked out from what looks like the back of the engine / where the gearbox joins the engine.

See my last post.

Thanks Brianmoooore.

So hopefully head gasket and a head skim and it should be OK.

Would there be any chance of bent valves, etc? Given there would have been water in the cylinders when the car was started. After starting the engine when I checked the coolant bottle it was completely empty. It had been to the fully mark a couple of days before.

Cranking a hydraulically locked engine tends to bend con rods, not valves, but the chances are that's OK.
There are lots of possibilities as to what could be wrong, and the only way to find out exactly what is to strip it down. Some possibilities will be a cheap repair, some won't, but it's clear that it won't be going anywhere until it's sorted.