Hello! I've recently bought a skoda pickup 1.3 mpi from 2000. I was gonna give it a bit of service and changed the oil filter and oil and noticed the coolant seemed quite bad, so I drained the coolant and topped it up while having the coolant sensor up.

 

I think at first I did it wrong since I had the car on normal flat ground but I tried a second time as it started to overheat after I tried driving it.

 

The second time I drained out the coolant and tried to see if I managed to flush anything out after draining the coolant and I didn't really manage to get any dirt out of it, this time I tried having the car raised up in the front a bit and opened the coolant sensor, I filled it so it was close to flowing out of the hole not entirely flooding out (should it be filled until it flows out of the hole and leaks out?) and I did notice air bubbles coming out, how long do you usually have to wait? I thought the air bubbles stopped coming out after around 2-3 minutes and put the sensor back and tried running it on idle until it got warm, but it still started going over the middle line on the temperature gauge. I noticed that the hose going towards the right side of the engine up to the heater isn't as warm as the other hoses.

Is it an air pocket that I didn't get out? Should I do it in any other way than what I've done? Maybe wait longer for the air bubbles to come out?

I've also had a thought of possibly trying to suck out the air with vacuum, is this possible? I have a vacuum pump at work that could work for that, or is it possible "the other way around" by pressurizing the system?

I had another thought, at what temperature is the middle line in the temperature gauge? That's where the temperature stayed when I was driving it after I bought it before I managed to brake it 😁, I assume its around 90 degrees since the thermostat is 88 degrees, the other two lines are 70 and 110 so I assume its gonna be around 90, I noticed that I never got the fan running either when I had it running, I never got it to go up to 110 I stopped it when it was maybe a quarter or closer to half between the middle line and 110.

 

It might also be possible that some residue or something came loose when I drained it and filled in new coolant and something clogged the heater I guess, is it easy to take the heater out and clean it?

 

Edit: forgot to mention, I've changed the thermostat including it's housing as I thought I might as well.

Edited 20 February, 20251 yr by ludvig
Forgot to add that I changed the thermostat.

Hi, welcome.

 

I do not know these cars (pick-up) so the following is just until those that do know come along.

 

If you do a (Google) search(es) on changing the coolant, thermostat and thermostat and problems from those it will bring you back to this forum with posts and threads on the subject(s)

 

Bits I (think) I know, mainly about older (than yours) car heating/cooling system.

 

It is a good thing you changing the coolant if it was bad but you'd also want really to fully drain the old coolant, flush the whole system, then back flush if possible, and drain out as much as possible to get as much old coolant and flush water, then put cleaner in and clean whole system, drain thoroughly, then flush and if possible back flush the whole system and thoroughly drain to get as much muck and residue cleaner and water out - before refilling with correct fresh new clean coolant.

 

I don't know how high or low the sensor is on your engine, or whether it is standard practice to remove this for refilling.

 

Generally for an old car for filling and getting the air out you want a high point for venting, or perhaps create one with the vehicle on level ground for filling normally, you squeeze pump a radiator hose to get coolant and air moving as you fill and/or as you warm the car up, have the cabin heater valve on hot as the matrix is usually a high point and you want full flow of coolant.

 

You can top up the radiator or expansion tank  as the engine runs and look for air bubbles too, how long each takes varies.

 

Temperature gauges tend to be biased to the 90 regardless of true number, the engine is not hot until it reaches the red section below that is just warmer than you are used to seeing.  The engine would be getting warm for the fan to normally cut in. 

 

If you use vacuum or pressure now surely you will get more coolant out than any air.

 

From what I can remember reading in posts on this forum the heater is not an easy thing to remove (otherwise you might want to remove it for better internal and external cleaning.

 

These old engines tend to have wider passages than modern engines but it is possible to get an air-lock and/or hot spot or blockage - do you have an engine block drain plug to remove and did you remove it and clean/clear its opening as much as possible?

 

I once left a piece of blueroll paper over the thermostat housing opening to stop anything falling into it and forgot it was there when I reconnected and filled the system, have you left anything in to block anywhere?

 

You put a new thermostat and housing in, are you sure the thermostat opens? 

 

Also there are threads and posts on here about getting the correct, and correct quality, thermostat and housing otherwise the new items can cause problem(s).

 

On a wider note servicing the car is a good idea, servicing the engine is more than an oil and filter change and that only covers the relatively unimportant engine.  As you can staged in between using the van I suggest you do a full 60/120,000 service and check on the whole van.  Priority, brakes, steering, suspension (all three include the tyres), safety electrics, (lights, wipers, blower, horn, etc.), windows, mirrors and reflective number plates (see and be seen).  Then engine and transmission.

 

Do not be too hasty with doing things, if the engine was cooling well before the coolant change then it is likely a simple thing to put things right, personally I would carefully clean the old thermostat and housing refit them and refill, and if required purge the system, and see if that resolves the issue - unless others think better and/or you have more information to give on this.

 

Good luck.

 

16 hours ago, ludvig said:

Should I do it in any other way than what I've done? Maybe wait longer for the air bubbles to come out?

 

All the connections are tight?

The expansion tank cap is OK?

For sure there is air inside the system, that's a bit normal when you have removed parts etc but it's easy to remove it in our system which has no radiator cap.

1) You make in a repair shop a ''pressure test'' to see if there are any leaks of coolant, if not then

2) Fill the system till the level in the expansion tank is in the middle, run the car slowly in the road at least 20' so the thermostat will open and the coolant level will drop

3) Squeeze the main hose many times, take a towel, grab the cap and turn it loose very slowly

4) You will hear s ''Hssss'' sound, that's good means air from the system is escaping out, when there is no sound screw the cap and turn off the car

5) Let the car cool normally and then check the level, add some one click above the middle between the Min and the Max marks.

 

Air inside the coolant system means temperature rising.

No air means higher pressure so you have protection from overheating.

I have done (far too) many coolant changes or top-ups from work on car or leaks over the decades on old and newer cars and other than the time I mentioned when I forgot to remove the paper towel I have always filled via the expansion tank when suitable or radiator on older cars.

 

I am not a mechanic at all, I carefully followed the instructions in the car's Owner's Manual (not the factory workshop manual or a Haynes) each time and have always had success first time and I never needed to squeeze any hoses but I accept it might help with some cars, should do no harm and it gives some reassurance.

 

Always best to check for leaks whilst the engine is running and when left parked up and next day.  Let the car fully go cold and check the coolant level and top-up as required and check again the next day and after the first run of the car.

 

Do not overtighten worm type (Jubilee) hose clips particularly when going on plastic fittings but you may be able to nip them up after a heat cycle (running the car from cold to hot and cold again) I check when the engine is both warmed up and cold - nip up only if required and not over tight.

 

Normally to get the air out you would leave the expansion cap (or radiator on much older cars) off and run the engine to warm it and watch until any air bubbles stop showing, also it gives no worry about releasing the cap when it is under pressure and the coolant is hot.  Having the cap off does not mean the coolant or engine will over heat, the pressure means a higher boiling point which your car should be nowhere near unless there is a real problem.

 

Only going on what has been put in opening post and past experience with old cars and modern parts quality as I put I would suspect the new replacement thermostat and housing might be a cause of overheating if the thermostat is not opening or not fully, this of course is a total guess and could well be wrong and even if the thermostat and housing are at fault there could also be other contributing issue to the overheating, never assume there might only be one cause to an issue, particularly when you think you have found that one cause always check everything else is working properly and fully.

 

Good luck.

 

Edited 21 February, 20251 yr by nta16

A no spill coolant filling funnel (burper) purge kit can be useful, the following is just the first video on the list, I picked it as he shows the instructions, instructions should be read and followed even when you think you already know, or know better - I can assure you many professional (they are getting paid) else workmen (almost always men) need to read instructions when they do not, I know I have employed them.

 

There are other videos you may prefer.

 

 

 

 

Edited 21 February, 20251 yr by nta16
spelling

I'm sorry I didn't write clearly, I changed the thermostat after it started becoming too warm after I had changed the coolant, so it was getting too warm before I changed the thermostat as well. Although it might still be the thermostat of course, but I'll try getting the air out first.

9 minutes ago, ludvig said:

 but I'll try getting the air out first.

 

No need to buy and install new parts without removing the air bubbles from your coolant system.

The thermostat sensor is OK? It's clean beneath? The cables are OK?

Your radiator fan works properly? The radiator switch works?

The coolant sensor works I have a correct gauge reading, never seemed weird and it is clean beneath, the radiator fan I don't know, at what temperature is it supposed to start running? I never got it to run earlier when it went slightly over 90°

Alright, I've checked the system has no leaks now, pressure testing it currently and it seems to keep pressure, had a little leak at the coolant hose to the thermostat housing, changed the hose clamp and it seems to seal now. Will try starting soon after having waited for a bit with pressure to see if it goes down or leaks somewhere.

Alright, been out driving for a while, first it didn't get fully warm but I finally got some heat from the heater, I kept driving it and it did fluctuate a bit in temperature eventually slowly rising to between the 110° and 90° marks then suddenly it decreased to between the 90° and 70° mark. I drove back to the workshop and checked the heat on all hoses and the radiator. Radiator was pretty cold and so was hose from the radiator but the hose to the radiator from the thermostat was hot and the heater hoses were hot. I pumped a bit by hand on the hoses and went out for another drive and it fluctuated a bit but then the fluctuations in temperature became less and less and finally I thought it was keeping itself at about the same temperature as earlier so I drove home and at highway speeds and it kept itself at the correct temperature. So I finally fixed it, thanks for all the tips they helped out a lot! 😁

Did you remember to unscrew gently the expnsion tank cap so any possible air will come out?

The coolnt sensor's ring is Yellow or Blue?

What's the range of the radiator switch? For example 90-95 'C?

 

48 minutes ago, ludvig said:

eventually slowly rising to between the 110° and 90° marks then suddenly it decreased to between the 90° and 70° mark.

 

That means that the thermostat is full opened but 110 'C is very high.

In my Felicia, one click above the 90 'C which means 92-93'C and the radiator fan starts spinning for a while.

 

It didn't open at 110, it opened between 110 and the middle line in the temperature gauge, which I assume is 90 degrees at first. Now it's at 90 and is behaving like normal no fluctuations in temperature and staying at 90 when I drive, all hoses and the radiator are the same temperature. It never got up to 110 only in the middle between the middle line and 110 degrees.

Also I remembered to gently unscrew the expansion tank cap. I forgot which color the coolant sensor was but I think it is yellow.

 

Sounds like you have sorted it, just a bit of trapped "wind as we say here when talking about the human body and "better out than in" when talking about natural human body activities - and often medically correct.

 

Do not forget to check for leaks and any clips that might need nipping up if those sort are used, when the vehicle is warm, cold and tomorrow and after next run, it is easily possible to have more than one weep/leak when you have a vehicle that might not have been attended to in those items for years or decades.  If the original type of coolant was used previously, and now, it should be changed every two years checking how well the antifreeze is working in the coolant is just one element of it the additive package includes for wear and corrosion protection and those deplete independently to antifreeze element of the coolant.

 

If you keep the pick-up you may want to clean the heating/cooling system more thoroughly in which case I've put notes on this on this forums IIRC a coupe of times and mentioned it more times.

 

Good luck, don't forget the important systems, components and parts on the vehicle, as I put the engine id lower on that list.

 

 

Thermostats do not spring fully or at their stated temperature, they start opening at (around) their stated temperature and are fully open at a higher temperature.  I am not sure  if you would notice when the thermostat starts to open on a gauge for a 1990s car, owners/drivers like D.FYLAKTOS would know for sure.  If there was an air lock that took the temperature out of the biased 90 range then you would perhaps see the drop on the gauge.

 

13 minutes ago, ludvig said:

no fluctuations in temperature and staying at 90 when I drive,

That reassurance is why they biased the gauge to remain steady at 90, which is fine you don't need to see the needle moving up or down a bit from that.

 

Yeah, I was planning to change brake fluid and servo steering oil as well, but I'm gonna do those later as those were in better condition and right now I have other projects that I need to finish. I changed the clamp to the thermostat housing as that one was leaking, I also accidentally had gotten some dirt between the hose and the thermostat housing which also helped create the leak. 

 

I've never actually experienced a cooling system being this hard to get the air out of, closest I've had to being this annoying was helping out with a Renault Master but that actually went fine eventually.

I've been planning to keep this car for a while maybe fix up the rust on it eventually, but that is a project for further in the future as right now I'm renovating a tractor and a bunch of other stuff..

4 minutes ago, nta16 said:

Thermostats do not spring fully or at their stated temperature, they start opening at (around) their stated temperature and are fully open at a higher temperature.  I am not sure  if you would notice when the thermostat starts to open on a gauge for a 1990s car, owners/drivers like D.FYLAKTOS would know for sure.  If there was an air lock that took the temperature out of the biased 90 range then you would perhaps see the drop on the gauge.

I don't know exactly when it opened, but that was when it dropped in temperature, which is why I said so. I might've been a bit unclear sorry.

33 minutes ago, ludvig said:

It didn't open at 110, it opened between 110 and the middle line in the temperature gauge, which I assume is 90 degrees at first.
 

 

 

 

That's mine, never above this point.

I have 80-85 'C radiator switch.

Check the brake fluid for fluid content, it is difficult to know the original colour of the brake fluid particularly if the plastic reservoir is dirty, discoloured, change colour with age.  Also obviously check the brakes as number one priority.  Tyres are a big contributor to braking efficiency, an old tyre can have lots of tread depth but tread and sidewall gone hard from age and lack of use, have a good look at the four of them and bear them in mind when assessing the braking efficiency and system.  Have a look at the production date on the tyres and see if the four tyres match for age, make and exact model, size (sidewall profile), obviously cracks, tears, splits, bumps, tread depth, etc..

 

Details of cleaning and changing the power steering fluid are on this forum too, if you cannot find anything just ask and a link can be put into a post.

 

Also details of changing gearbox oil, details of cleaning suggestions if required can be added.

 

18 minutes ago, D.FYLAKTOS said:

That's mine, never above this point.

I have 80-85 'C radiator switch.

Yep, that's where mine is as well, sorry I was a bit unclear but it's keeping itself around the line in between 70 and 110, just like in your picture.

 

9 minutes ago, nta16 said:

Tyres are a big contributor to braking efficiency, an old tyre can have lots of tread depth but tread and sidewall gone hard from age and lack of use

The tyres are good I checked them when I bought the car.

Lots of people forget to change brake fluid so I am going to do it as soon as I have time to do it. I've worked on some vehicles where brake fluid was probably barely ever changed and it can get really sludgy and break a lot of things..

22 minutes ago, ludvig said:

I don't know exactly when it opened, but that was when it dropped in temperature, which is why I said so. I might've been a bit unclear sorry.

No your English is great don't apologise.  Sometimes driving the car is a good thing on fluid changes as it shakes the bubbles to the top, same with slightly spongy feel to brake (or clutch) pedal after fluid change,  For brake/clutch fluid change I use the one-man-with-jar (fluid at bottom for air seal) method, you can do this with an ABS block fitted.  If you don't have ABS I would seriously see about changing to silicone (DoT 5) to save changing again in 2 years and save the paintwork.  So many myths about DoT 5 on the internet and with cold car people, a mate his it in his 1969 since he restored and rebuilt it 25+ years ago and he doesn't drive that like it is a museum piece but as it was designed to be driven when new.

 

You have G11 or G12?

G-wotever, the Germans with their unnecessary additional specifications for coolants and engine oil (on top of the VW numbers), I think they might have changed the numbers and specifications sometimes to help with the engineering compromises and mistakes with their engines and gearboxes since the start of this century.

 

Only the other day I added a line to one of the VW coolant charts, check the notes at the bottom.  It's not great but it was a first attempt as I can't remember where I got this chart from.

 

 

34 minutes ago, nta16 said:

DoT 5

I'll think about changing it to DOT 5, as I don't have ABS, but you do need to change the seals then right if I don't remember wrong? Because I really hate working with brake fluid because spilling it anywhere is hell.

The coolant that was in it I don't know really since it wasn't the best looking the color was a bit off, it probably wasn't original either as it wasn't really blue/green, red or violet.

I tried to flush out as best as I could the old coolant out of the system with water and I got out most of the old dirt and I also took loose the expansion tank and tried to flush it out and get it as clean as possible too because it was quite dirty and had some sludge stuck in it. It wasn't oily or anything so I don't think it's a head gasket or anything I just think it was very dirty or some coolants that were not supposed to mix put in there, which was why I wanted to change it and flush it out.

Yes I thought you had to flush and clean the brake system too but a few years back an older chap in his 70s with a 1940s/50s car put how when he was flushing the brake system found a mix of DoT3 and Dot 8 DoT 5 in the system as it came out with a clear line between the two and the brakes had been that way since he bought the car - and when that mate I mentioned bought my 1973 car with DoT4 in it he told me just pushed it out with putting the DoT 5 in he told me.  His job is working on "classic" car racing engines he doesn't follow the usual classic car myths and rules he does what he knows works.  I wished I had know I could have save lots of time hassle and money over the decades of old cars ownership.

 

Now these are English cars using the brake systems and parts we used over here you would have to check about your brakes - but over here I was told seals needed to be replaced and one manufacturer says not to use Dot 5, possibly for in America but the 1940s/50s car despite being English made was for American export with English parts on it (England needed the money from exports after the Second World War, some of it to pay back the money, and interest, from the Americans!

 

Edited 22 February, 20251 yr by nta16
5 not 8

Yep, I'll have to check if I might change to dot 5 then, I always found brake fluid (dot 4) to be stupid, why would you ever use anything that absorbs water but there's probably a good reason I assume but seems like dot 5 or for an example LHM, although that would require changing the seals.

Edited 21 February, 20251 yr by ludvig