How to Fix Heater Problems - MG-Rover.org Forums
 
 
 
Go Back   MG-Rover.org Forums > Ask The Gurus! - Help and Advice Forums > How Do I - Answers To Common Problems.

Reply
 
Thread Tools Rating: Thread Rating: 4 votes, 5.00 average. Display Modes
Old 08-12-2010, 21:00   #1
1955diesel
Never forgotten
 

Join Date: Jan 2005
Location: Birmingham
Car: Other Manufacturer. Previously - more Rovers than I care to remember.
Posts: 16,734
Question How to Fix Heater Problems

The information here is mainly aimed at Rover 200/400 but much of it also applies to other models.


Rover 25
- Coolant flows from outlet on front of head to heater control valve, then through heater matrix and back to the thermostat where its temperature is used to control the stat opening. When the heater control valve is closed, coolant by-passes the matrix and flows through the rubber block between the pipes directly back to the stat.


MGF Cooling Circuit with Standard Thermostat -




MGFT Cooling Circuit with PRT type Thermostat -
(Diagram by Titanium)






First off – does the heater fan work?

If it does not work on some speeds and this is the problem then refer to this thread. If the heater fan does not work on any of the speeds then the problem is more likely to be a fuse or the fan motor itself. If the heater fan works, but the air is always cold then the coolant has stopped flowing through it, the coolant is cold or the hot air control flaps are not working correctly.

Lack of flow through heater matrix can be due to:

Freezing – thaw out and make sure that coolant is up to strength and changed at regular intervals. Freezing can also cause much more serious damage to the engine and other components.

Heater coolant valve seized / Cable Problems
– the control valve in the heater feed pipe under the bonnet should open and close as the temperature knob is turned. On Rover 200/400 models it is situated near the bulkhead where the heater pipes go through and is operated by a cable from the heater. If it does not move fully, try to work it free with some WD40 or similar. If the knob feels sticky to turn then also read this thread. Or if the knob spins freely it may just be loose on its spindle and need replacing. MGF valve operation is described here, and MGTF heater cable adjustment is here. Another bent control cable thread is here. And another faulty TF valve investigated here.

Typical Heater Valve and Mechanism.



Heater matrix blocked – this can be caused by mayo deposits following a head gasket failure or corrosion debris due to poor system maintenance. Flush through both ways with a hose pipe then run the system with degreaser or descaler in it before refilling with antifreeze mix (coolant). It is often difficult to clean the matrix completely because as soon as a clear path through it exists, the flush will take this route and the remainder will stay blocked. Also, system cleaners will not work where there is no flow at all.



Air lock – perhaps the most common and usually caused by allowing the coolant level to get too low or by incorrect filling from empty. This usually (but not always) results in the engine overheating because it can stop flow through both the heater and the heater by-pass and this will stop coolant from reaching the thermostat in order to open it. System should be topped up with antifreeze mix and if the heater still blows cold the system should be bled to get rid of the air locks. Links to bleeding are –
http://forums.mg-rover.org/showthrea...901&highlight=
http://forums.mg-rover.org/showthrea...697&highlight=
MGF only - http://forums.mg-rover.org/showthread.php?t=351375
Note that mayo deposits left in the cooling system, especially if they block vent pipes, can make this process very difficult!

Vapour lock - similar to an air lock, but caused by steam from localised boiling within the engine. The difference here is that when things cool down it will get better by itself as the steam condenses. This is usually caused by a leaking filler cap allowing pressure to escape from the system. The caps are known to be unreliable - buy a new one.

SAAB (Ranco) valve malfunction – late cars had their heater by-pass controlled by a black plastic valve
instead of just a restrictor. This looks like a T piece and is in the heater pipes near the coolant control valve. If this valve falls to pieces, it can block off the heater and allow all the coolant to take a short cut back to the engine. If this happens, the heater may still get hot when the engine is revved up. It may be possible for the valve to be replaced with a 4mm restrictor, but I am not aware of anyone trying this yet. Perhaps it would be easier to replace the entire system with the heater hoses from the earlier car.

Blocked Oil Cooler - High performance versions of the MGTF and 75 have a water fed oil cooler fitted. This forms part of the heater/by-pass circuit and can easily become blocked by mayo following head gasket failure.

Water Pump Impeller Failed - If the water pump impeller has corroded away or become loose the flow may not be sufficient to warm up the heater matrix, but things may improve as the engine speed is raised.


Coolant passing through heater too cold caused by:


Thermostat problem – thermostat failed partly open, thermostat has been removed or someone has drilled a hole through it. Beware! If you find that there appears to be no thermostat fitted, check to see if the vehicle is fitted with a PRT type stat in the pipework. These cars still keep the old thermostat housing, but there is no thermostat inside it, just a carrier for the gasket.

Last edited by 1955diesel; 08-07-2011 at 19:37.
1955diesel is offline   Reply With Quote

Sponsored Links
Advertisement
 
Old 13-12-2010, 18:53   #2
1955diesel
Never forgotten
 

Join Date: Jan 2005
Location: Birmingham
Car: Other Manufacturer. Previously - more Rovers than I care to remember.
Posts: 16,734
SAAB (Ranco) Valve

The SAAB valve is situated between the engine and bulkhead in the pipes that provide supply and return to the heater matrix, just before the coolant control valve. The valve is the component in the middle of the second picture with the silver label on it. Earlier systems do not have anything in this area and the link between the two pipes is made inside the block of rubber connecting them at the top of the picture.

When the heater valve is close, water still has to flow back to the thermostat in order to control its opening. This is done by a heater by-pass connection between feed and return pipes. The SAAB valve was introduced in an attempt to increase coolant flow through the heater matrix by closing off the by-pass when not required.

The valve closes off the by-pass when the heater valve is open and then opens fully to allow flow when the heater valve is closed (Cold position). Failure mode seems to be that it sticks open or the washer goes missing increasing flow through by-pass and starving heater. The failed parts can also get into the pipework and cause havoc!

Rimmer Brothers no longer stock the original system with no valve so if you wanted to change back to it the scrap yard might be the only source. Or you could try making up a DIY solution using a 4mm restrictor in place of the valve to act as a by-pass. It might even be possible to eliminate it all together if the original by-pass link inside the rubber block still exists. You would have to check this because I'm not sure if they blanked it off or not. Anyone know for sure?




Original Rover 25 Heater Feed and Return Hose Assembly with no Valve.



Late Type Rover 25 Heater Feed and Return Hose Assembly with SAAB Valve.



SAAB Valve







A couple of diagrams from saabcentral.com -
Labels apply to Saab, but are similar to Rover. (ignore reference to manifold in second diag)



Last edited by 1955diesel; 25-04-2011 at 18:07.
1955diesel is offline   Reply With Quote

Old 27-12-2010, 19:33   #3
millar
Registered User
 

Join Date: Jan 2009
Location: kirkcaldy
Car: MG ZR
Posts: 480
I am going to change my pipe work and saab valve tomorrow.

I will have a look at my old valve and try see if I can re jig it to incorporate a 4mm restrictor. If this is successful I will give it to someone on here to try it out on their car for the price of postage
millar is offline   Reply With Quote

Old 29-12-2010, 15:16   #4
PedsR6
Registered User
 

Join Date: Mar 2010
Location: Manchester
Car: MG ZR
Posts: 2
Hi, I had the problem of no heat so i changed the valve at the bulkhead and had no joy. I also had the problem of the fan only workin on 3 & 4 so I followed your top instructions and got the part from the scrapyard fitted it, all is good. Still had no heat so while the glove box was off I looked under the dash and there is a purple cable that fits on to a push and pull lever which had come off,put it back on and instant heat. Just thought i would post this before you strip your car like i did.
PedsR6 is offline   Reply With Quote

Old 29-12-2010, 19:55   #5
HotTubRepairer
Registered User
 

Join Date: Jan 2007
Location: Lincolnshire
Car: Astravan 165
Posts: 12,190
Send a message via MSN to HotTubRepairer
Thanks John.

I'll add this thread to my 'how to' sticky in the 200/25/ZR section. It's great info.

Cheers,
HotTubRepairer is offline   Reply With Quote

Old 03-01-2011, 12:41   #6
FrKevin
Supporter
 
FrKevin's Avatar
 

Join Date: Jul 2008
Location: Bromley
Car: MG TF
Posts: 887
Is this a similar setup on my 04 45 Diesel? It takes for ever to warm up and heating to work, unlike my TF?
FrKevin is offline   Reply With Quote

Old 07-01-2011, 15:31   #7
rich91
Registered User
 

Join Date: Jan 2011
Location: W.Sussex
Car: 414iS
Posts: 12
Heater problem, R414

Thanks, John, for much useful info on heater.
Mine just blows cold air for past 2 weeks, so will have to get a mechanic to sort it out. I wish I had a workshop in which I could attempt my own repairs. Hope its not head gasket....
Rich.
rich91 is offline   Reply With Quote

Old 18-01-2011, 16:20   #8
rich91
Registered User
 

Join Date: Jan 2011
Location: W.Sussex
Car: 414iS
Posts: 12
Well, John, have just paid local mechanic 730 for repairs to my R414iS.
Head gasket blown, oil & coolant all mixing, so coolant system completely flushed out. New 3-part head gasket, head machined, 2 valves reground, new water pump, new cambelt, new steel rods. On 75k miles for an 11-year old car. The wife will do her local trips in it for a few more years. We thought it better to spend the cash on it than risk 3k+ on a younger motor with unknown problems.
R has 4 newish tyres, brakes relined 6 months ago, some welding underneath at the same time, and few other signs of wear - apart from the odd rattle!
Rich
rich91 is offline   Reply With Quote

Old 31-01-2011, 08:33   #9
paul evo
Registered User
 

Join Date: Jan 2011
Car: Streetwise
Posts: 2
Quote:
Originally Posted by PedsR6 View Post
Hi, I had the problem of no heat so i changed the valve at the bulkhead and had no joy. I also had the problem of the fan only workin on 3 & 4 so I followed your top instructions and got the part from the scrapyard fitted it, all is good. Still had no heat so while the glove box was off I looked under the dash and there is a purple cable that fits on to a push and pull lever which had come off,put it back on and instant heat. Just thought i would post this before you strip your car like i did.

could this be the same on mgzr ? 04 plate ?
paul evo is offline   Reply With Quote

Old 05-03-2011, 14:11   #10
1955diesel
Never forgotten
 

Join Date: Jan 2005
Location: Birmingham
Car: Other Manufacturer. Previously - more Rovers than I care to remember.
Posts: 16,734
Image of SAAB valve (marked in yellow) on 04 plate ZR as posted by MyfirstMGZR+



Not sure if the rubber block between the pipes still provides a by-pass between them. Any one know for sure?
1955diesel is offline   Reply With Quote

Old 22-03-2011, 08:46   #11
iturner15
Registered User
 

Join Date: Nov 2009
Location: Bournemouth
Car: MG ZR Mrk2
Posts: 7
Hi guys,

sorry to bring up an old thread but just wanted to say thanks for the info! I've had problems 'bleeding' my coolant for months now... yesterday I replaced my saab valve and all the pipe work around for the old system as above, heater worked straight away! Very happy!! And, the old version was only 2 from a scrap yard, not 68 as the new part is from rimmer bros!

Cheers,
Ian
iturner15 is offline   Reply With Quote

Old 20-07-2011, 16:25   #12
ChrisJames
Registered User
 

Join Date: Jul 2011
Location: Croydon
Car: MG ZR
Posts: 15
Hi guys, just got my new ZR and the fans are blowing cold. After reading a few threads I'm still not sure of the best way to tackle the problem. I've been on a 100 mile round trip and have done about 500 miles in the last week and there has been no problem with overheating, and no cooling/ oil leaks. Should I start by flushing the cooling system, and if that doesn't work change the thermostat? (as these are both relatively cheap, easy things to do). Other than those things I'm not really sure what to do.

Any advice would be much appreciated!

Cheers, Chris
ChrisJames is offline   Reply With Quote

Old 20-07-2011, 19:05   #13
1955diesel
Never forgotten
 

Join Date: Jan 2005
Location: Birmingham
Car: Other Manufacturer. Previously - more Rovers than I care to remember.
Posts: 16,734
Go through all the points raised in the first post, probably in the order as listed.
1955diesel is offline   Reply With Quote

Old 22-07-2011, 18:03   #14
ChrisJames
Registered User
 

Join Date: Jul 2011
Location: Croydon
Car: MG ZR
Posts: 15
Right so going down from the top..

The fans work fine, and there's no problem with the coolant valve mechanism (the cable and switch are both working fine).

I've bled and flushed the system in effort to get rid of blockages and air locks and the heaters are still blowing cold.

There's no circulation problems and the engine does not overheat, and I'm not loosing any coolant at all. One thing I did notice is that the heater feed pipe (going into the coolant valve) was very hot (after running the engine) but the return hose (leading out of the valve) was luke warm. I don't know if this means there's something wrong with the heater mechanism inside the coolant control valve, not letting water through, or if the Saab valve is related to this in any way??

Any advice would be much appreciated!

Cheers, Chris
ChrisJames is offline   Reply With Quote

Old 22-07-2011, 18:16   #15
1955diesel
Never forgotten
 

Join Date: Jan 2005
Location: Birmingham
Car: Other Manufacturer. Previously - more Rovers than I care to remember.
Posts: 16,734
I can't add anything that I've not already said in the posts above. If there is a big temperature difference across the heater matrix it indicates lack of flow. Could be a blocked matrix or the valve itself blocked. If you have a SAAB valve it may have fallen to pieces. But these points have already been covered.

Best thing to do is to get the hose pipe out and start flushing the system and testing for flow one pipe at a time. Bare in mind that the matrix can be very difficult to clear fully. Often just one small pathway will open up through it.
1955diesel is offline   Reply With Quote

Old 20-08-2011, 20:14   #16
G0MRL
Registered User
 

Join Date: Mar 2006
Location: Bolton
Car: TF135, MG3, Jag S 2.7D
Posts: 1,107
Quote:
Originally Posted by FrKevin View Post
Is this a similar setup on my 04 45 Diesel? It takes for ever to warm up and heating to work, unlike my TF?

The reason your diesel is slow to warm up is that diesels are more efficient and there is less waste heat. My ZS diesel took about five miles to reach a heater friendly water temperature - a bit of a nuisance in frosty weather.
G0MRL is offline   Reply With Quote

Old 21-08-2011, 13:05   #17
DieselYank
Registered User
 

Join Date: Aug 2011
Location: Kentucky USA
Car: 2009 VW Jetta TDI
Posts: 734
Quote:
Originally Posted by 1955diesel View Post
I can't add anything that I've not already said in the posts above. If there is a big temperature difference across the heater matrix it indicates lack of flow. Could be a blocked matrix or the valve itself blocked. If you have a SAAB valve it may have fallen to pieces. But these points have already been covered.

Best thing to do is to get the hose pipe out and start flushing the system and testing for flow one pipe at a time. Bare in mind that the matrix can be very difficult to clear fully. Often just one small pathway will open up through it.
Nice thread! Don't know if this is covered above, but Prestone used to sell a kit to attach to the heater core inlet for flushing. I'd get a similar kit and flush from the outlet side real hard. A hose with 2 clamps might work as well.

Used to use Muriatic Acid for a radiator flush. Makes brass and Al shine. Really caustic so use with caution. Test the solution on a piece of dirty metal if you do that.
DieselYank is offline   Reply With Quote

Old 05-09-2011, 13:21   #18
dazzahu
Registered User
 

Join Date: Sep 2011
Car: Rover 25
Posts: 1
Red face Rover 25 Heater Probs!

HI Guys, i need some help I have a Rover 25 1.4 2005 model and my friend who is a mechanic has just replaced the head gasket, for some reason the heater has stopped getting warm, he has bled the system 4 times, we have hosed through and cleaned the matrix and replaced the thermastat all to no avail, we are really scratching our heads and need some help! the water pump seems to be working fine too,

any ideas?? thanks in advance
dazzahu is offline   Reply With Quote

Old 03-10-2011, 17:30   #19
tommyb23
Registered User
 

Join Date: Jul 2007
Location: Cape Town
Car: MG ZR
Posts: 373
Quote:
Originally Posted by dazzahu View Post
HI Guys, i need some help I have a Rover 25 1.4 2005 model and my friend who is a mechanic has just replaced the head gasket, for some reason the heater has stopped getting warm, he has bled the system 4 times, we have hosed through and cleaned the matrix and replaced the thermastat all to no avail, we are really scratching our heads and need some help! the water pump seems to be working fine too,

any ideas?? thanks in advance
read the thread again from the top.
i dont mean to be rude its just every possible situation is listed all nice and in one thread.
Diesel what a thread. ++
thanks for using my pics of the bypass valve
tommyb23 is offline   Reply With Quote

Old 20-10-2011, 10:12   #20
knighty101
Registered User
 

Join Date: Jul 2006
Car: Rover 200 Cabby
Posts: 3
Thumbs up

Hi Guys, sorry if I am going over something that's already be said however I would like to be 100% sure before I swap out pipes.

I have a 55reg rover 25 which has a T valve which has failed meaning I get no heating. now I still have the old pipes from a rover 200 which had no T valve, therefore can you confirm if would it be ok to just to switch out the pipes and put the rover 200 pipes (which had no T valve) on to my 55 plate rover?

many thanks
knighty101 is offline   Reply With Quote

Reply

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Cold Heater spaceoctagon MGF and MGTF (Sponsored by MGFnTFBITZ) 5 09-01-2010 15:16
heater on cold. Goldy. MG ZS / Rover 45 & 400 13 08-10-2009 23:53
Car heater never warms up in the cold only when driven cigarette powered heater? Jem. Diesel Forum! 13 14-01-2009 19:21
Yet another cold heater! ChrisEeley MG ZS / Rover 45 & 400 0 21-11-2008 16:06
Cold heater myrova MG ZT / Rover 75 (Sponsored by Rimmer Bros) 2 31-07-2006 22:25


All times are GMT. The time now is 15:51.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
ShowCase, Vendor Tools vBulletin Plugins by Drive Thru Online, Inc.