Strange coolant behavior

[Jester B]

In my 2.7t, when I start from cold (in the morning), the coolant temp is very slow to come up to 90. It blows warm air throgh the heater core and when I step on the gas it blows HOT.

Coolant temp sensor is new (3 months) - green
Thermostat is new (1 week) and similar problems existed before it was replaced (didn't check vent temps though)
No codes

Thoughts?

Vapour lock?

How to fix?

[Kor]

Re: Strange coolant behavior

For once, I have no ideas.

[Canadian Turbo]

Re: Strange coolant behavior

Maybe a problem with the gauge/needle itself, just not moving as quickly as it should be??

[stefan]

Re: Strange coolant behavior

For once, I have no ideas.

someone document this..

[Jester B]

Re: Strange coolant behavior

LOL

I don't think it's the gauge.

When I sit at a light it blows warm. As soon as I accelerate (normally), off the light, it blows hot.

Nobody has seen this before?

[stefan]

Re: Strange coolant behavior

Reminds me of my old toyota, but it was the other way. hot at idle, and cold on accel. The heater core's valve was vacuum powered, and the vacuum would drop when I took off and close the valve to the core because I has a leak in the vacuum system.
Not that this has anything to do with your issue...

[RSS]

Re: Strange coolant behavior

I know this is not what you want to hear but it sounds like heater core issues and that's never a good thing on a B5. Did you search Audiworld yet I think you will probably find a similar case there.

[Jester B]

Re: Strange coolant behavior

I did search AW, but I am not using the correct terms...no relevant results. I can't see it being the heater core, though. I don't know how a problem there would impact overall water temperature and how it's very VERY slow to warm up.

[R_Ethug]

Re: Strange coolant behavior

did you post on AZ/AW?

[Jester B]

Re: Strange coolant behavior

Found this thread...added to it.
http://forums.audiworld.com/27tv6/msgs/4546.phtml

Also discovered I have a secondary air pump that is failing.

[VWSM]

Re: Strange coolant behavior

water pump disease

[Ehfour]

Re: Strange coolant behavior

In my 2.7t, when I start from cold (in the morning), the coolant temp is very slow to come up to 90. It blows warm air throgh the heater core and when I step on the gas it blows HOT.

Coolant temp sensor is new (3 months) - green
Thermostat is new (1 week) and similar problems existed before it was replaced (didn't check vent temps though)
No codes

Thoughts?

Vapour lock?

How to fix?

not sure either, but a simple check would to make sure you don't have any air in your coolant system. There are 2 bleeder valves you can purge (at least on my 2.8) and then at the heater hose into the heater core, if you haven't already checked this, just a thought.

[Volkstech01]

Re: Strange coolant behavior

Check your flow, maybe put a infared pyrometer on hose during warm up to watch thermostat, sticking?? just cause it's new doesnt mean it's good.

[Jester B]

Re: Strange coolant behavior

an infrared pyrometer? What the heck is that? Would George have one?

Thought it could be possible to have a bad tstat.

Would a coolant powerflush be worth trying?

[Volkstech01]

Re: Strange coolant behavior

Not sure who George is, infared thermometer is all it is. You can watch temps @ upper rad hose and lower rad as stat opens, not sure where you would find specs for time but I'm sure you would know when too long is too long. there are specs though, or even known good 2.7t and compare but I would check flow rate, pull return off bottle, hold in opening and watch flow @ idle and high rpm, it's gonna be one or the other.