Was it bled correctly form all 3 bleed points? Did you clean out the coolant system of any gunk from the HGF? Try giving it a good bleed again.

 

I bled it all using the 3 bleed points.
There was no gunk in the water from the HGF. The oil was very comtaminated though.
In honesty, I didn't flush it out, just drained it and re-filled.
Would that make a difference? It's not overheating.

 

How was the matrix when you bled it? they sometimes get blocked? especially after HGF. I dont think flushing is standard after repairing but i'm trying to think of some easy causes.

 

I was quite happy that all of the air was out. The heater was amazingly good and I had no issues for the 1st 300 mile. I've read about blocked hoses though and perished hoses letting air in. Also the inlet manifold gasket failing but I replaced that when I did the HGF.
I'm just at a bit of a loss. Suppose I could flush the system out then get a sniff test.?

 

This couldn't be something as simple as a failed expansion tank cap could it?? If it has been bled up correctly then it is the only other thing I could think of.

 

yes it could i had the same issue after a HGF, water popping out the expansion tank. If the cap is not properly sealing the tank, air will get in and build up pressure.

 

if your cap is broken water will seap from the expansion tank around the cap. If the cap is fine no coolant shoudl escape at all and if there was a pressure problem the cap would simply blow off. Try a new cap, only £6 ish.

 

1st thing I purchased this morning. New cap fitted and still the same.

Well I've just flushed the whole water system through. Opened all 3 bleed points and stuck the hose pipe in the expansion tank.

Left it flushing for about 20 mins. I checked all the hoses and tightened a couple of jubilee clips.. Then ran it and tighted up the bleeds. Ran it until hot then bled again. Got some air from the heater but not much else.

Took it for a drive and its still doing it. After driving about 20 min the heater started to go cold. Temp gauge didn't go up but I pulled over and slowly undid the expansion cap and released the pressure.
It took ages but once it was released, I refitted the cap and drove home.
Pulled up on the drive and I can hear the tank bubbling again.

Anyone have any other ideas??? Don't fancy doing the head gasket again!!! (Oh and the oil is clean).

 

Did you change the thermostat? Did you check the height of the liners?

 

I didn't change the thermostat. It gets up to tempreture quickly and is fine until it starts to pressure.
Whats this about the liners? I didn't check them for level. They seemed strudy enough when I was working in there.

 

You need to check that the liners sit slightly proud of the block. If they are lower then you will not get a proper seal you could be pressurising the water with compression from the cylinders.

 

Cylinder liners can drop or crack allowing the hot gasses to come into direct contact with the coolant which causes localised superheating. This superheating only really happens after the cylinders have heated up and therefore the crack has chance to expand so about the 20min that your getting.

One thing though, the temp gauge usually shifts quite rapidly if this is the case.....

Unless you have an air pocket at your sensor in that case you wouldn't detect much, you'd just get the bubbling at the tank, as the steam created by the heated coolant is released.

How much coolant are you losing?

If its not much then the crack will be small and therefore not letting coolant into the cylinder when cold, but will be letting pressurised gasses out when hot.
If its quite a bit the crack could be bigger and be letting that coolant into the cylinder and therefore into the sump gradually at standstill.

Mayo on the dipstick is the red flag warning of this however an easy check for that is to undo the sump plug for a second, water/coolant drops to the bottom as oil floats on it so will shoot out first. If you get a water/oil mix out then its bad news and an engine strip down job.

If you pop the bonnet and feel the top of the radiator when the tank is bubbling is it hot?

 

Thermostat?

I read somewhere recently (will see if I can find it) about the thermostat not opening and the pressure building as a result.

 

MGF Header tank pressure

Hello all.

Thanks for your help so far. Heres where I am with it.

I have today replaced the thermostst. And for the record, what a *&£* of a job.
What was Rovers design brief with the MGF? Make everything as hard as possible to maintain? No bolt must be accessable with out removing engine parts or if it is, the just a quarter turn of the spanner is allowed.
Oh and any one who works on the car MUST have blood drawn from their hands.
Sorry Rant Over.
Right, as I said, I changed the thermostat. I put the old one in a bowl of boiling water and it didn't open. So I felt quite confident that was the problem.
New one it, re-assembled everything. Filled the coolant and bled. Took it for a blast up the motor way and all seemed fine. Gotall the way round with no loss of heater or temp rising.
When I did pull up on the drive and check the expansion bottle, I found that it was still chucking water out of the cap. (Already replaced)
Could this just be a settling in period or maybe another bleed required?

Failing this, it looks like either HGF again or problem with the liner.

HELP!!!!!

 

Oh and the oil is still clean. No sign of Mayo.

 

This sounds exactly the same as what mine has done, had the thermostat replaced and it is still bubbling in the header tank and overheating occasionally. My local garage did some checks on the bubbling and found out it was exhaust gasses

 

I had this problem with my ZT 1.8T. Liners were low and thought exhaust gasses were in the coolant, but turned out to be a blockage.... turned out that the garage that had fitted the new head gasket had fitted a new thermostat in the thermostat housing. Unknown to them, when a PRT is fitted, the thermostat housing is just a dummy (no thermostat). The new thermostat was acting as a blockage, thus sending water back through the cap!

Have you upgraded to the PRT system? It's a common upgrade.

 

No, Its not got the PRT. It was fine for the first 300 miles then suddenly started pressuring.
I'll give it a bleed in the morning. If thats not it, I guess its down to the gasket or liners.

 

Let's hope it's not the liners, fingers crossed.

 

Any one got any ideas?

Well....

I've just purchased a Gunson compression tester today and tested my MGF.

All 4 cylinders achieved 178psi after 5 turns. So it looks like I've not got a cracked liner and I'm not losing compression.

Had it running on the drive for about 40 mins with the fan cutting in and out ok. It did't over heat, boil over or loose heat from the heater.

I've taken it for a 10 mile blast up the bypass and back and found that it seems to be perfectly ok. I got stuck at a level crossing where the temp went up to one notch above half whilst standing but once moving again it went straight back down.

Could the previous issues just have been an air lock and its cleared now or am I living with false hope?

With good compression in all cylinders, I'm ruling out HGF and cracked liner. So what else can cause the header tank to pressure too much.
I've had now cap and thermostat. Can't see any leaks anywhere and no water on the floor even after being stood ticking over for 40 min.

Any One Have Any Ideas?

PLEASE?????

 

Well....

I've just purchased a Gunson compression tester today and tested my MGF.

All 4 cylinders achieved 178psi after 5 turns. So it looks like I've not got a cracked liner and I'm not losing compression.

Had it running on the drive for about 40 mins with the fan cutting in and out ok. It did't over heat, boil over or loose heat from the heater.

I've taken it for a 10 mile blast up the bypass and back and found that it seems to be perfectly ok. I got stuck at a level crossing where the temp went up to one notch above half whilst standing but once moving again it went straight back down.

Could the previous issues just have been an air lock and its cleared now or am I living with false hope?

With good compression in all cylinders, I'm ruling out HGF and cracked liner. So what else can cause the header tank to pressure too much.
I've had now cap and thermostat. Can't see any leaks anywhere and no water on the floor even after being stood ticking over for 40 min.

Any One Have Any Ideas?

PLEASE?????

For my money your stat was duff and there has also been some trapped air. They can be a right bugger to bleed as I found out at the weekend. Bleed once, bleed twice and bleed again to be sure as it is easy for a pocket of air to be trapped. I stood for 1 minute with the nipple on the coolant rail removed before it decided to clear its throat and rush out!

Having coolant come out of the rad doesn't prove it is bled. If there are any bubbles at all with it then it isn't bled, there should be a silent stream of coolant emerging when bled right.

 

With any luck it was an air lock that has belched its way out. Good consistant cylinder pressures don't prove the HG is good though. Can you get the coolant analized for exhaust gas? If you have gas into the coolant you won't see mayo on the dipstick.

 

I was looking for a sniff test today but haven't managed to find one. If it happens again I might have to book it into a garage to have it tested. Hate paying garage prices.

Hoping it was an airlock!

Thanks.

 

Arrived at the party late but hope its sorted now Pete, did you do the comp. test on a warm or cold engine?

Not that it matters because of course is solved now that you know the duff 'stat was causing the backup of pressure

 

I warmed the engine up first. I was hoping to get nearer 200psi but the car is 12 years old.
Fingers crossed its ok on the next outing.

Thanks everyone.

 

I would say 178 would be fine. The fact that they are all the same. Is good too.


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I believe that the normal recommendation is that the expansion tank cap should be changed annually in any event.

The factors leading to HGF typically include:

the K series engine was bored out from 1.6 to 1.8, this led to narrow walls between the cylinders, not an issue except thast the gasket was also necessarily narrow

the 1.6 also suffers failures but is more tolerant due to wider gaps

expansion cap failures leading to increased pressure in the cooling system

hard driving before the engine is warmed up leading to thermal tension in the block

the water pump is borderline for the engine size

all K series engines have this potential including Rover 200 series. petrol Freelanders, many others - the Elise K series has two water pumps I believe and is less susceptible

leaving the engine hot and switching off causes thermal t6ension in the engine bay - always warm down after a run

Any other thoughts guys?

 

dont forget to post the outcome - as ive got this exact problem, had it pressure tested with no problems showing other than 3 faulty caps in a row but looks to still be doing it, am going to bleed through again later and hope its just an airlock somewhere

 

Hi all. Just joined the forum today. I have a 2003 rover 75 1.8 saloon. I had a HGF failure last year August. I had a mobile mechanic replace it with a uprated triple layer gasket, it needed a new head (newer head) which was skimmed and pressure tested before assebling all back together. The car was fine for about a week til we went to the coast on a short break at around 250 miles into the journey it hit over temp. The car was towed back home. The mechanic did another head gasket change, head checked. The car was fine for a day but it hit over temp again?? There was no coolant in it. After looking on this forum I replaced the coolant cap. filled with coolant. Still was losing coolant. Called a local rover specialist and took the car to them to look at it. the place is 20 miles away drove the no problem no loss of coolant no over temp, they had it for 3 days. They changed out the oil (previous mech had not done this??) and oil filter. they found no leaks and it did not hit over temp? I drove back from the garage and pulled up in tesco's to see coolant just coming out of the expansion tank? Again I looked to the forum and someone suggested the thermostat. I subsequently found that I have a PRT I bought a new one a rimmer bros and fitted. Flushed the coolant system and bled it. At idle the car was not losing coolant. the heater in the car was hot. I took the car for a run out about 30 miles stopped the temp gauge at 9 0clock no coolant escaping. Heater left on hot the whole time. Driving back home the became cold? The temp started to climb to overheat. I looked at no coolant in tank?? Filled up with water and drove home with no more overheating?? All this time I have checked the oil and dipstick no 'mayo' car engine has no loss of power and seems perfectly fine driving? Please help I'm at a loss. Spent too much money already? Love the car but its getting rediculous now?

 

Water Pipe??? Help & Advice please.

Hello All.

I'm still trting to sort out this presure problem with my F.

Been out for a long steady drive today, no motorway. After about 30 / 40 minutes the temp starts rising so i know the new stat hasn't solved it.
Once I got it home I lifted the front end and notices the passenger side steel water pipe looked wet.
Water was behind the paint / coating on the pipe.
I peeled off the paint to reveal a shiney pipe but with a tiny hole the size of a pin *****!!!
Is it possible that this is sucking air in and creating an air lock and over pressuring the coolant system??
Whats my best and cheapest option for replacing?
Is a repair possible / practicle?

Thanks in advance for all you help!

 

Looks like you need new coolant pies. Go for SS replacement at about £60 to £70.

They're available from several suppliers, ie B&G, Rimmers, Mike Satur, MGOC, etc.