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Fri Jan 24, 2020 10:40 am

Hi folks,

My 2.1 Syncro has been running pretty well until about a week ago when the temp needle shot up, heater blew nothing but cold air and the header anks boiled and pushed everything out into the expansion.

I bought some coolant and followd the bleeding guide and everything seemed ok. Heater has been blowing hot air but occasionally the temp needle will jump up to 3/4 cold air will blow through before it settled back and the heater blows hot again.

Today i topped up the header and expansion, bled through the radiator screw, rev'd, bled, drove etc etc and everything seemed fine. Needle was settled, radiator getting hot, fan blowing hot air and no more air bubbling out of radiator. Took another small drive and when i got back after another 10mins of idling the needle shot upto 3/4 header boiler and pushed it all out into the expansion.

Has anyone got any thoughts on what the issue is? Is it likely to be the head gasket that needs changing or is there something else i should investigate/try before putting it into the garage.

Many thanks!

Fri Jan 24, 2020 10:57 am

This should help:

https://intrepidoverland.com/bad-coolant-pressure-cap-or-bad-head-gasket/

Fri Jan 24, 2020 11:32 am

Very helpful! Looks like i have a fire ring failure and will have to replace the fire rings and head gasket.

Sat Jan 25, 2020 2:12 pm

If you see bubbles streaming into the pressure tank you have compression gases getting into the coolant. Time to pull the heads and do the o-o rings and seal.

Sun Jan 26, 2020 8:31 am

dabaron wrote: If you see bubbles streaming into the pressure tank you have compression gases getting into the coolant. Time to pull the heads and do the o-o rings and seal.

Read my article and you won't be quite as certain. Coolant vapor bubbles can also be entrained in coolant flow and show up in the pressure tank, especially on the 1.9 system.

Quote: Very helpful! Looks like i have a fire ring failure and will have to replace the fire rings and head gasket.

The crux of the article is that the key thing that differentiates a fire ring leak from a bad pressure cap is if you bleed the radiator of all gases, take a drive until you see your symptoms, and check the radiator while still warm and it has gases in it again, it's a fire ring leak. You won't see gases in the radiator from a malfunctioning pressure cap, but in some cases you might see bubbles rising in the pressure tank from either. Some cases, in my experience a minority but seeing them doesn't prove a fire ring leak, gases in the radiator that don't recondense does. In the case of a bad p-cap, the bubbles in the tank are coolant vapor, in the case of a fire ring leak, they are combustion gases. Neither are air, and the reason you must check the rad for gases while still warm, besides the warm system having the pressure to drive them out, is to be sure there isn't a leak that draws air into the system as it cools down.

Sun Jan 26, 2020 9:26 am

Thanks for the clarification tencent