Heater goes cold, engine temp needle goes up...

Post by **ringo** » 07 Oct 2008, 17:21

Driving 90 miles this morning i was getting these symptoms. The further i got the more often it happened. It didnt seem to have any relation to how i was driving or up hills etc - just periodically happen.

I just checked the water level and it was a bit down (ie half a pint) - but interestingly the expansion tank was full to the brim (ie had more than what i put in).

I've just filled up and bled the system - so i hope this cures it - however, i havent found a leak yet.

Anyone got any ideas as to what i might be experiencing - or is it just simply a leak letting air into the system?

A bit annoying - but one of those teething problems with a new engine install i suppose.....

Thanks

Ringo

Post by **jamesc76** » 07 Oct 2008, 17:27

Mate normall symptoms of exactly what you put is even badly bled, head gasket or water pump problems sorry to be the bearer of bad news! sounds like the water system is spresuring up!

Post by **Mocki** » 07 Oct 2008, 17:29

airlock........
as it moved from the waterpump, the temp needle moves to reflect the difference in temp between water and air , then later it goes round the heater rad, changing temp against your knee, then back to the engine, and as the air is pumped around the air bubble join together to make a bigger airlock and it happens more for longer ,

bleed it properly, front up, revs up ect......

then when you think its all done, do it again, and then if it developes again, there is either a leak, or something is pushing air into the system....

Post by **ghost123uk** » 07 Oct 2008, 18:41

ringo wrote:
A bit annoying - but one of those teething problems with a new engine install i suppose.....

Ringo

Sounds like the fairly common T25 flat 4 airlock problem.
iirc there is info in the club80-90 wiki about bleeding techniques.

E D I T = of course being an AAZ it is not quiet the same as a flat 4 petrol is it

However it could be pressure getting in from a head gasket or even a cracked head.

Was this engine a new one or a used one ?

Post by **T'Onion** » 07 Oct 2008, 18:47

its a diesel

live with it , gives you something to do

Post by **Ian Hulley** » 07 Oct 2008, 18:48

ghost123uk wrote: Sounds like the fairly common T25 flat 4 airlock problem.

It would if it weren't for the fact it's a 1Y oil burner

Ian.

Website · Post by **syncrosimon** » 07 Oct 2008, 19:02

Just slightly of topic, but how does the front heater matrix stay air free, there is no bleeder is there?
If there isnt then how does it do it??

Post by **ghost123uk** » 07 Oct 2008, 19:20

ghost123uk wrote:
Sounds like the fairly common T25 flat 4 airlock problem.

E D I T = of course being an AAZ it is not quiet the same as a flat 4 petrol is it

Post by **T'Onion** » 07 Oct 2008, 19:28

fire wall forward its the same , and sounds like thats where the air lock is

Post by **ghost123uk** » 07 Oct 2008, 20:06

Don't forget there is a bleed point at the top r/h of the rad.

Best to get that corner as high up as poss then try bleeding there, after running the motor at a fast tickover till warm.

Post by **ringo** » 07 Oct 2008, 20:15

thanks for the replies - it's an AAZ that I just transfered from my other van. The engine was fine. I'm going to go with the air lock theory before I start panicking. I bled it and there was air in the system. The likelyhood that there is a leak is high as o only installed it last week!

Will see how it fares on the journey home.

Ringo

Post by **ringo** » 09 Oct 2008, 18:42

Well, i have a very slight leak in the top of the radiator bleed screw - anyway, i need to change the copper washer and clean all that up.

Today, driving back i had exactly the same problem - i drove from Cambridge to Peterborough where it overheated (needle right to the top) (i had the heater fully off) - the needle was going up and down from the minute it reached thermostat opening temp.

I pulled into Peterborough services (eyup Martin

) and had a look - nothing going wrong there. Water had gone into the expansion tank but im guessing thats because the water temp was right up.

So, i topped up and set off - this time with the heater on full blast.

Absolutely no issues.

I put the heater on half way, and after a while the heater went cold and the temp started to go up.

I then put the heater on full blast and everything was fine. In fact, even driving it like i stole it i couldnt get it to overheat.

Why oh why does it makes so much difference if i turn the heater down?

Bizarre.

Anyway, im going to Cromer - it might be a bit hot!

Ringo

Post by **Ye Olde Syncrospares** » 09 Oct 2008, 18:51

headgasket.

Post by **ringo** » 09 Oct 2008, 19:53

SYNCROSPARES UK wrote:headgasket.

What makes you say that?

Im not disagreeing with you - just curious.

Im still struggling to get my head around the fact that it runs perfectly when the heater is on full (cruising for an hour at 60) and then 10 minutes after turning the heater to half way the heater went cold and the temp creeped up.

Maybe the head gasket has gone near to the heater channel (ie the end of the block) and having water go over it full flow stops gasses escaping ?

I appreciate your help...

Thanks

Ringo

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Heater goes cold, engine temp needle goes up...

Heater goes cold, engine temp needle goes up...

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