new user needs help with sudden overheat and no heat

Longitudinal · Post by **Longitudinal** » 11 Oct 2012, 00:08

Hi,

My name is Jonathan. My girlfriend and I bought her a 1994 850 turbo from a friend. Things started out well, but the engine overheated and cracked the reservoir cap. No problem, I thought, thinking that the broken cap was the cause rather than a result. I replaced the cap, which had to be replaced, but the engine still overheats. In fact, it overheats rapidly. The needle will take off after a couple minutes of driving and will soar within seconds from mid-way to the top of the gauge.

At the same time, there is NO heat in the cabin.

The top radiator hose gets nice and hot and the bottom remains ice cold.

Thermostat, right? I pulled it and dropped it into a bowl of microwaved water at the boiling point. It didn't open. Great! For the first time in my life, I saw an actually bad thermostat! Bought a new one. Decided to test the new one first. Guess what...the new one doesn't open either. Tested a used VW thermostat I had lying around. It opens-and it is nearly the same in dimensions as the Volvo piece, so I installed it. No difference. Temp gauge still rockets to the top and the car still has no heat.

So... No heat, engine overheating, bottom hose stays ice cold.

I'm thinking either a suddenly plugged radiator or a broken water pump impeller.

Thoughts?

Post by **rspi** » 11 Oct 2012, 05:39

I have seen a broken water pump impeller before so that is possible.

1. Is the system full of coolant? (You sound like you know what you're doing so my guess is yes)
2. Is the head gasket destroyed? (These cars have pretty soft heads, one overheat can warp them).
3. Does water drain out the RAD easily with the valve open?
4. You may try this... Disconnect the heater core hose from inside the engine compartment and start the car, if you don't have water force, maybe the water pump is not pumping.

How old is the timing belt?

Post by **boosted5cyl** » 11 Oct 2012, 06:22

Busted water pump or a blockage somewhere. The heating system will work regardless of the thermostat being open or not. The heater core is on the same circuit as the block/head.

Longitudinal · Post by **Longitudinal** » 11 Oct 2012, 08:01

Yeah, I was thinking about what I said yesterday and realized that a blocked radiator wouldn't deny the cabin heat.

It will have plenty of coolant--until it gets hot. The system definitely has some sure in it, witnessed by how far the expansion tank's level drops after the engine has cooled down. A hot engine has a full tank and a cool engine has an empty tank.

Post by **erikv11** » 11 Oct 2012, 08:02

I agree, radiator clogged or water pump is shot. Opening the drain cock won't really help you figure out a blocked radiator because that will also drain water out of the engine. But if you drain the system and pull the lower hose, then water should flow freely through the radiator. If it does, then that points to the water pump.

Unfortunately rspi makes a good point: hopefully the head isn't warped.

Post by **Ozark Lee** » 11 Oct 2012, 08:51

Is it actually overheating? I have had a couple of them where the temperature gauge behaved much as yours does but I traced the problem back to a bad Engine Coolant Temperature sensor. In my case the gauge was heading for the red before I got around the block but it was not boiling over at all.

Until you figure it out, don't drive it.

...Lee

Longitudinal · Post by **Longitudinal** » 11 Oct 2012, 11:31

Thank you so much for the replies.

Are the water pump impellers likely to be plastic?

I would say that it is overheating, although my first imputation of what was happening was that it had a bad temp sender because the temp would rapidly rise, then fall to cold, then go to normal, then high again, and so on.

Post by **Ozark Lee** » 11 Oct 2012, 11:44

The decent quality water pumps like the OEM Aisin and the HEPU have stainless steel impellers but there are some cheap brands (likely some auto parts store re-built) that do have plastic impellers. if it is a re-built you really don't know until it is removed as it will still have the name brand cast into its face.

...Lee

Post by **boosted5cyl** » 11 Oct 2012, 11:50

I would have said temp sensor, but since the heater core is cold that leads me to think its a flow issue. I think some of the pumps have fiber impellers but most commonly they are metallic AFAIK.

Post by **cn90** » 11 Oct 2012, 12:26

Overheated engine and no heat in cabin = Broken Water Pump.

As Lee said, STOP driving the car until you figure it out.

For WP, use either Aisin (OEM) or Hepu. The price difference is $10.