Jump to content

Air lock / temp issue


Recommended Posts

Hello Me again!

Manta 1.8s previous problem was top hose, bottom hose cold & radiator cold temp rising. So, new thermostat fitted got top hose heating and radiator. While at it checked timing belt and water pump and all as new. Put back together and ran in garage, all warmed and temp sat in the middle of scale for fair length of time so all seemed good,  temp went up a bit thermostat opened temp fell back. All good. Heat from heater but just warm. 

Taxed the car and off we went, ok for 6 miles or so ,,,temp rising slightly over normal. Checked under bonnet and bottom hose cold.  Heater hoses hot, top hose and radiator top hot but not overly so, System had pressure so cap working .Drove back and temp sat just over normal and just under the next white mark,... never went past that and not near Red. Home 12 miles now and bottom hose still cold. Squeezed it with rad cap off and water did "burp" so rad not blocked. and had flushed it and put new antifreeze in. 

Thought air lock but cant clear it. 

Still think it is and air lock - ideas? Is there a knack to bleeding air out? I ran it topping up radiator as we filled it, squeezed bottom pipe,....


Any advice welcome, Im certainly getting good value from membership!

Work tomorrow but intend to have another crack at it on Friday 





Link to comment
Share on other sites

Did you bleed it with the heater on full 

if that's not it might be worth flushing the heater matrix 

also jack the car up high at the front whilst bleeding 

good bit of info in this post 


Edited by garymanc
  • Like 1
Link to comment
Share on other sites

Forgot I had written that !

The position of the heater flap makes no difference, the matrix is always a part of the cooling system so you can bleed with it in cool or hot.

ITs only when running up to temp you need to check the heater matrix is hot so that's when you need to select hot on the control.

Very often poor heaters are caused by an air bubble up the top of the matrix, the same air bubble that we remove in the bleeding procedure above !

Link to comment
Share on other sites

Forgiv3 me if I’ve misread something but are you looking for a fault that isn’t there. 

Do I understand correctly. Car drives fine ,never goes into red. Just goes slightly higher than middle .heater working but not very hot ,water level ok and no other issues ?

the heater working but not very hot could likely be just partly blocked .ive had new heater cores in the past and they are realy hot but a few years down the line and a dose of Barr’s and performance can drop off. I would suggest a good heater core flush with hose pipe both ways to be sure but they never seem to get as good as when new,

there could be a small air lock in the heater core but I’ve never ever experienced it myself ( on a cam in head lump thou)

as regards the bottom hose .it will always be much cooler than the top one as the hot water enters at the top of the road and exits at the bottom.

any other issues ?


  • Like 2
Link to comment
Share on other sites

Just to double check for you .just drove home today and felt hoses.

top radiator hose very hot as expected.heater inlet hose very hot.outlet slightly less so but bottom radiator hose much cooler ,almost cold compared to everything else so can't see you have any actual issue . But was worth checking for you

  • Like 2
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    • No registered users viewing this page.
  • Create New...