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Old 05-09-2008, 19:25   #1
kanewesley
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Heater in car blowing cold....Please Please Help !!

WE are going mad...please help....
My stepson has a ZR......last week he had the head gasket changed because the car overheated and would not start....what we though was due to a possible radiator leak.
To cut a long long story short the heater didnt work before this HGF and neither does it work now.
We have bled the system many many times a day for a week now. Still no heater.
He took the car out the other night and suddenly he noticed the temp very high.
He stopped , checked under the bonnet, and set off again and the engine ran normally !!!!! but still no heater.
We think the water pump may be at fault and performing so weakly or failing intermittently, it is not able to shove the water around the heater matrix.....only possibly shoving enough water around the system to keep the engine runnable with the temp gauge almost half way. We have taken the pipes off and started the engine and watched to see how efficient the pump actually pumps water......hardly anything.
there are no screeching or grinding or vibrating noises form the pump.....we think the impeller may not be driving as it should to shove water round the system.
The original failure of the HG may now have been due to this water pump not performing and NOT a leaking radiator.
Are we right in what we are thinking or are we way off track?
How can we check the performance of the water pump?
We have backflushed every water pipe and the heater matrix so we are confident there is no blockage.
There has been a new thermostat fitted, HG, head skimmed, timing belt and head bolts.
Can the water pump be driven by the timing belt but not pump any water round?
I know this doesnt seem right as the engine is not overheating ( has done twice I know....once with main failure and 2nd time the other night) but generally the temp. gauge is just below half way.
Is it possible for the pump to work barely enough to keep the engine running but not drive water through the heater matrix?
Please please give us any clues you have.
Thanks in advance.
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Old 05-09-2008, 20:44   #2
jase32
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If everything else has been changed except the water pump I would probably guess that the water pump is the fault. They only cost about 20 and are easy to fit.
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Old 05-09-2008, 23:56   #3
Tony White
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Unfortunately, And I'm very sad to tell you this, If it is indeed the case but if the engine overheated during it's last HGF then the head may have gone soft and may now be scrap.

Sorry.

If the head is soft it can cause airlocks and would stop the heater blowing hot/Warm air.

If the heater only blows cold and you have bled the system correctly then I'm afraid it sounds like the car needs a replacement cylinder head from a scrap yard.

HGF is a well known problem with the k series engine but there are methods available now to combat the chances of HGF.

Before deciding that this is the reason for your car's problem, It is worth considering whether the cooling system was cleared properly after it's HGF because it is alot of hard work to do a good job.

You can try some speed flush to see if it clears any blockage in the cooling system.
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Old 06-09-2008, 07:00   #4
1955diesel
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If the engine will run without overheating, it would suggest that the problem lies purely with the heater.

The usual reason for the heater not blowing hot is an air lock as suggested. However, this would go together with the engine boiling up after a short time. This is because the heater and its plumbing are used as the engine coolant by-pass circuit. Persistent air locks can be caused by the head gasket leaking as mentioned in the last post. As your engine does not boil up, I don't think this is the problem.

The only other things I can think of would be a stuck heater valve, but you have flushed the system and so eliminated that one. Or perhaps the air control flaps inside the heater unit have slipped?

If the water pump was not pumping, you would almost certainly have major overheating problems.
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Old 06-09-2008, 09:11   #5
Tony White
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Sorry, Yes I may have jumped the gun a bit here and it is worth trying other stuff first.

Quote:
Originally Posted by kanewesley View Post
Can the water pump be driven by the timing belt but not pump any water round?
If the blades have rusted off or if the bearing is heavily worn, Then yes, Possibly.

Quote:
Originally Posted by kanewesley View Post
How can we check the performance of the water pump?
When you bleed the air off the system, A steady stream of coolant should bubble slightly out of the bleed hole before you turn the engine off to complete the air bleeding process to get rid of any air locks.

Truthfully, You can only truly tell by removing and therefore replacing the pump.
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Old 11-09-2008, 12:00   #6
geordio
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I've got a similar sounding problem, and its not looking good so far, beginning to dispair.

Car (1.4 ZR) overheated last week, heater only blowing cold, thought I had noticed in time before doing damage, but now not sure. AA came out, said HGF. Fortunately, I know a few people that know K series pretty well, so was able to get new gasket fitted, head skimmed at a decent price.

Was no obvious signs of HGF though, water and oil had only just started to mix, so no mayo, head looked fine, but had it skimmed anyway.

However, the same symptoms still exist, overheats, loads of pressure in coolant system, and no flow of coolant.

Had thermostat changed, new water pump, still not fixed.

Had another gasket changed, this time with new head.
Still got the same symptoms again... arrggghhh.

I'm sure its been bled properly, stand proud heights of liners are all in tolerance (just).

Don't know what to do next.

Chap doing the job knows the k series inside out and he's running out of ideas. suspects problem with bottom end, but what???

Any suggestions?

Thanks
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Old 11-09-2008, 12:10   #7
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I had something similar to that a while ago. Head gasket has never gone on it and one night wondered why with the heater at full and on hot setting why i was getting cold air. i stopped to check under bonnet and thought the radiator had burst but there was no sign of leaking or anything. as soon as i got near my house i noticed the temp gauge creeping up everytime i went above 30 in 5th gear. wen i got home i check under bonnet and still could not find anything wrong apart from the coolant bottle being a bit low so i left it and in morning all was fine until engine had fully warmed up then temp guage rocketed so i checked under the hood and noticed a bit of bubbling coming from top corner of radiator. it had burst but the water or coolant only comes out when the engine was under a force i.e when you actually press the throttle and in gear driving so when i was stopped nothing came out.

Thats just what happened to me dont know how relevant or if it helps at all lol
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Old 11-09-2008, 17:48   #8
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Just a simple thought - did you have the heater set to hot when you bled the system? Need to do this or the heater matrix will remain airlocked.
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Old 11-09-2008, 22:16   #9
geordio
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Quote:
Originally Posted by maverick123 View Post
Just a simple thought - did you have the heater set to hot when you bled the system? Need to do this or the heater matrix will remain airlocked.
thanks for the response...

yep, heater on hot when trying to bleed. hoses up to the the heater matrix are red hot, pipes actually on the matrix cool. checked that theres not blockages in the matrix itself. even tried bypassing the matrix, still no joy

frustrating stuff...

cplnoonoo, symptoms sound similar, I had a look for leaks but nothing obvious, I will double check though. mine seems to happen even when at idle. getting so much pressure that i would hope i could spot something obvious.
will hopefully get the engine pressure tested at the weekend, not sure if that might help highlight an issue.

the joys of k series lol!
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Old 12-09-2008, 06:18   #10
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LOL swop it for an L-series, lot less bovver , and join us dervheads, it's a more exclusive club than petrolheads
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Old 17-09-2008, 11:06   #11
geordio
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Update:
Had coolant system pressure tested, cylinders leak tested, all passed.
vac filled the coolant, car ran fine, hot air in cabin, no overheating.
Took of cap if the expansion tank, level rose and then sank back down, but now have original symptoms again, cold air in cabin and overheating, seems like has airlock again.

Where could the air be getting in if the leak test etc all passed? any ideas anyone?
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Old 17-09-2008, 11:26   #12
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sounds very similar, if not the same as what my TF is doing! the garage currently thing airlock so this thread suggests that is correct!

sorry i have no idea where the air might be comming from but i will be watching this thread very closely!

oh, just a thought, did you replace the expansion tank cap any time recently? if it not sealing it could be allowing coolant to boil up and create air bubbles in the engine?
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Old 18-09-2008, 11:54   #13
Tony White
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Quote:
Originally Posted by geordio View Post
Took of cap if the expansion tank, level rose and then sank back down, but now have original symptoms again, cold air in cabin and overheating, seems like has airlock again.

Where could the air be getting in if the leak test etc all passed? any ideas anyone?
Very likely from when you took the cap off when the engine was hot and the coolant was under pressure.

Quote:
Originally Posted by MyRomeo View Post
oh, just a thought, did you replace the expansion tank cap any time recently? if it not sealing it could be allowing coolant to boil up and create air bubbles in the engine?
If the level rose when the cap was removed when the coolant was under pressure, Then I guess the cap is not at fault here and it seems like the coolant system is holding pressure.

I wouldn't drive it at all if you can't get the heaters to blow hot.
It may blow another gasket.

I can only think that you either aren't bleeding the system correctly or releasing the coolant cap whilst it's under pressure causes an airlock.
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Old 20-09-2008, 12:31   #14
geordio
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sorted problem!

actual problem was caused by the coolant hose. On the later cars (post 04MY?) there is a Saab T piece, which contains a spring, a little bit of plastic and i suspect its also supposed to have a ball in there, but mine didn't. Swapped hose for older version, and it bled straight away. dunno where the ball went if it was there in the first place, but can't see what the assembly is supposed to do without one.

very relieved anyway.
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Old 20-09-2008, 17:27   #15
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Glad its sorted for you. Sounds like you have had a right ball ache
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Old 30-05-2010, 14:50   #16
scottyg555
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mg zr heaters

Hi mate. Think iv got same problem you had with heaters. Could you tell me where u got the t piece valve part from and what you asked for? Thanks.
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Old 31-05-2010, 00:30   #17
matrix MG
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i managed to get one from a scrapyard off a k-series they had laying around... still got the old one, trying to figure out how to disassemble it to recondition it.

the valve is actually a Saab part, it should cost around 50 new, if you can find one.
i asked EMG ford in kings lynn who are an x-part dealer, who in turn asked every x-part dealer in the uk. no-one had any even though it aparrently used to be a stock part, so obviously a known problem.

best bet would be to have a look in some scrap yards and see if any cars still have them on.
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Old 15-09-2010, 20:36   #18
omega2498
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Saab bypass valve

Have a look for the `my mysterious heater' thread. The Saab valve disc lets go and winds up in the side port of the thermostat housing.
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