97 Jetta Overheat Problem

[ThatTDILife]

Ok guys, so I was making a 3 hour trip to visit some friends today and about 30 minutes into the trip I had some issues. I am driving up a hill going inbetween 75 and 80 and all of a sudden some steam came out from under my hood and I lost a good portion of my power. I pulled off the next exit to see what broke and I couldnt see anything, so I topped off the coolant and set back off on the road after letting it cool down. Then i plugged in my obd2 scanner and watched the temps. About a minute into my drib=ve the temps went up to 270 so I pulled off and had it towed home. I did some quick diagnosing and I noticed my radiator fans were not spinning and my fuse wasnt blown. Also my car started up with no problem and the gauge wasnt going up until like 240. Could I have blown a head gasket and what other diagnosing could I do to see why it overheated and why the fans were not spinning. Sorry about the long story and the cluelessness, i'm new to tdi's but not new to vw's. Than ks in advance

 

[Steve Addy]

Unless your AC is on the coolant fans don't typically run unless it's hot and you're stuck in traffic.

The first consideration is the elevated temp, which could be a faulty thermostat, which does happen sometimes. Or a failed water pump, which also happens.

The fans not coming on might be due to a bad CTS or bad wiring, which is not uncommon on a car of this age either.

My first look would be at the thermostat & water pump, especially if you've not had a problem with temps before.

Steve

 

[ToddA1]

Yeah, the fans won't likely come on at highway speeds.

When the car is warmed up, compare the upper and lower rad hoses. If the lower hose is colder, it's one of what Steve mentioned. Easier to just replace both.

It's not terribly hard to replace the pump from the top. Timing belt will be untouched, but that lower hose connection is a pain.

-Todd

 

[Steve Addy]

My 97 Mk3 lost first water pump at 64k miles (prior owner) and the next at a shade over 150K miles. These were both OE dealer installed pumps too.

Todd is correct about checking hoses for temperature deviation. I should have included that.

If you don't have a MK3 Bentley manual it would be good to get one, they're very common and with so many Mk3 cars evaporating daily from rust they're not hard to find.

Steve

 

[ThatTDILife]

Thanks for the replies guys, I checked more on the fans today and they didnt spin when I turned on my ac, granted it was from a cold start. I will check the radiator temps right now and get back to you guys. Ive replaced a thermostat and water pump before so that wont be too bad and I also have the p1255 or something like that code for temp sensor

 

[ThatTDILife]

Ok, I checked the radiator hoses and they were both warm, if anything the lowere oine was slightly colder but I also didnt get a firm grip on it so I couldnt tell for sure if it was.

 

[ToddA1]

Both warm is good. When you replaced the pump, was it with a a plastic impeller? Bosch brands use plastic. I've had one of those slip at highway speeds. At idle, it was fine.

Check impeller slippage by pulling the thermostat, shoving a screwdriver or something else up there and attempt to hand spin the pulley.

-Todd

 

[ThatTDILife]

I havent ever replaced the water pump as ive only had this car for like 5k miles. I just pulled the lower radiator hose off and turned the car over to see if it would pump out any water but it didnt. So I think the water pump is gone. Still worried about the power loss that I had when it over heated though

 

[Steve Addy]

I havent ever replaced the water pump as ive only had this car for like 5k miles. I just pulled the lower radiator hose off and turned the car over to see if it would pump out any water but it didnt. So I think the water pump is gone. Still worried about the power loss that I had when it over heated though

It didn't pump out any water because the thermostat is closed. It's just behind that flange. The only coolant that came out was from the radiator.

In order to do Todd's test for water pump impeller you need to pull the lower plastic flange off the water pump (must remove PS pump and bracket first) and then you can reach the impeller with a screw driver or some other object.

While you're checking your water pump though I would heat a pan of water on the stove bringing to a boil with a thermometer and check your thermostat to see if it opens when it should. It should open quite a ways, if it doesn't open much consider just replacing it with a new one, you'll need the o-ring gasket as well.

Good luck!

Steve

 

[Abacus]

Your water pump is working if flow is coming into the coolant bottle. It won't be a ton, but it'll be present. The hose on the side of the coolant bottle is the return from the pump.

I did have a strange case where a metal water pump impeller stopped working but was fine upon diagnosis. I had an epiffany one night and when I checked the pump the next morning, I applied a little heat to simulate running conditions and sure enough, the impeller would spin, just not when cold. I had already swapped it out but was glad I figured out the problem. It did cause the head gasket to leak so I had to swap it.

 

[ThatTDILife]

Ok, ill check the thermostat tonight aswell as the coolant bottle flow. I also have a crack in my
coolant bottle cap but that hasn't caused any problems before. I took it out for a quick drive
yesterday night and it was only a few miles and the car was overheating in the short drive.
Before yesterday I would drive the car to school in the morning and it is about a 35 minute drive.
Im guessing something messed up when I took it to highway speeds even though I didnt go
much over 75 and hit 80 downhill once.

 

[ToddA1]

That cap is designed to hold around 15psi. That crack isn't helping.

-Todd

 

[ThatTDILife]

I'll pick up a new cap for it while I'm replacing things

 

[ThatTDILife]

Ok guys, I took out the thermostat and I put it in 190 plus degree water and it opened up. No a bunch but it did. I'm gonna replace it anyway but is there any other things to check?

 

[Steve Addy]

Hmmm...since I didn't see it hard to say whether it opened enough or not. If you say it didn't open much I think it ought to be replaced.

If it were me I'd replace the plastic flange too, they tend to be a single use item or at least in my experience they like to break if they're reinstalled.

New flange should come with the thermostat o-ring too.

Also, what color coolant is in your car? Is it G12 or G13?

Steve

 

[Abacus]

No question to replace it, they're cheap. Just use a good one and not something Chinese.

 

[ThatTDILife]

Im not sure what type of coolant it is the orange one lol. It opened up about an quarter of an inch maybe a bit more. Tomorrow I'm gonna pick up the new one and the new gasket. ill order the cap and thermostat housing aswell. Once I install the new thermostat i'll check the coolant bottle for flow to figure out if the water pump is bad or not. If its not the water pump or the thermosta it would have to be a coolant blockage I think. And if the head gasket is gone would that make it over heat?

 

[Steve Addy]

Is it orange or pink coolant? Big difference.

VW specified coolant, currently G13, isn't that expensive and should be used, but you'll need to get it from the dealer most likely.

overheating is a potential sign of bad head gasket but it's not generally the first thing that a person jumps too because it's the most drastic. Start with the cheap easily changed things first before we move on to the more difficult.

Steve

 

[ThatTDILife]

Ok, so I've put in a new thermostat and seal. I know the water pump is working and it will stay at a good temp while idling with the heat on but as soon as I start to drive it and get a minute down the road it gets too hot and I have to bring it back. Also the bottom radiator hose is not getting hot, could there be a blockage in the radiator?

 

[ToddA1]

Did you shove a screwdriver up into the impeller?

-Todd

 

[ThatTDILife]

No what impeller?

 

[ThatTDILife]

Oh and there is no leaks aswell

 

[Steve Addy]

Both warm is good. When you replaced the pump, was it with a a plastic impeller? Bosch brands use plastic. I've had one of those slip at highway speeds. At idle, it was fine.

Check impeller slippage by pulling the thermostat, shoving a screwdriver or something else up there and attempt to hand spin the pulley.

-Todd

as highlighted above

Your water pump is working if flow is coming into the coolant bottle. It won't be a ton, but it'll be present. The hose on the side of the coolant bottle is the return from the pump.

I did have a strange case where a metal water pump impeller stopped working but was fine upon diagnosis. I had an epiffany one night and when I checked the pump the next morning, I applied a little heat to simulate running conditions and sure enough, the impeller would spin, just not when cold. I had already swapped it out but was glad I figured out the problem. It did cause the head gasket to leak so I had to swap it.

as highlighted here too.

The thing is, it doesn't matter if the system is fully sealed or not if the water pump isn't circulating coolant, and that's with the thermostat open or closed. It just takes a different route, that's why Abacus suggested watching the coolant reservoir when the water pump was operating, to see if there was any coolant getting sent back to the reservoir via the small hose.

If the car overheated again with the thermostat replaced I have to think there's either something wrong with the water pump or you have a more serious issue with the engine, like a head gasket failure. Are you losing coolant when the car is running and it gets hot?

Can you give a little more history of how this started and what if anything happened before the start of the overheating? Did it happen out of the blue or were there indications that something was wrong?

Steve

 

[ThatTDILife]

There were no prior indications of over heating. Sometimes the temp gauge would go above normal but it would go back down. It did get really hot when on the high way but nothing lead me to believe that there were any prior issues and no leakage

 

[kooyajerms]

THe temp gauge going above normal is already a sign of overheating. It's a dummy gauge. It doesn't truly reflect the temperature, just cold>normal (160-200) and anything above is overheating. It could be 40*f over normal without pegging the gauge.

 

[ThatTDILife]

Sometime next week I'm going to rent a compression test kit and check the compression

 

[ThatTDILife]

Ok, I was trying some more stuff today when I noticed a very light drip from the front of the engine. I traced it to a small crack in the block. Don't know where to do from here now

 

[Abacus]

I'd clean the area and confirm its a crack in the block. It's more likely to be leaking above the area and running down to that point. These engines are pretty tough and so long as there was no external damage, it's unlikely the block is truly cracked.

Is the area on an aluminum section? Because if so, then that's most likely the water pump housing, which I have seen fail more than once.