Coolant temp sensor - wrong size replacement

[Santa2512]

Now thats interesting ,

 

when you say misfire,  i thought my sons felicia is doing that, but as you say   when you put your foot on the throttle it chugs and then clears.  but it idles smoothly at 900    

 

His is a 1.3 BTW

 

If you go to the exhaust end, and listen it dosent sound like a misfire  more of a  pressure pulse .

 

If it was a misfire, why only at low RPM  and not through the whole rev range ?

 

If i was carb, it would be a blocked idle jet, but as its multipoint injection .. 

 

If i can get my VAGcom  to work i'll have a look at the engine data and see if anything is amiss.

 

It may be just a characteristic  lol

 

[Fio]

Ok so today i have cleaned the map sensor, also another sensor attached to throttle body (not sure what it is).

 

When I removed the map sensor there was a visible film of oil/residue and also inside it on the metal sensor part. Here is a photo, you can see some dripping/film on the top. Coated it in brake cleaner, and electrical contact in the plug and gently wiped the outside, careful not to damage the fragile bits.

 

I haven't removed and cleaned the throttle body, but the rubber ring on the air intake pipe, which snugs over the top of the throttle body, was coated in oily residue, also a bit around the top of throttle body. Breather pipe is a bit black inside too, but not wet. Anyway cleaned all this too.

 

So this was to see if it would help with the loud chugging feel and sound when fast idle 1100 on start up, which I thought could be related to coolant temp sensor. The loud chugging resonates around the front cat heat shield, and at the rear of exhaust like a pressure pulse as you say (sounding a bit like a chopper ) and feels similar to a misfire vibration in the cabin.

 

Anyway started it up and the idle is at 1100 as before, only now the chugging and noisy exhaust note is absent. It takes about 1 min for the revs to slowly drop to 900 from a cold start ( I think thats normal..)

 

There is some engine vibration at idle, not extreme but you can see it vibrating slightly. The ht leads are old and may be contributing? Spark plugs 2000 miles.

 

Took if for a drive on some b-roads to open it up and hopefully clear its throat . I'll see how it goes from here, but seems to have made a noticeable improvement cleaning the map sensor. Might be to do with the short journeys I'm guilty of. Thanks for the help chaps.

 

 

[RicardoM]

9 hours ago, Fio said:

The ht leads are old and may be contributing?

It's possible but misfire is a topic in itself. There are many things that could cause a misfire. Electrical related (dirty/corroded/cracked dizzy cap, worn carbon brush, cracked ht leads, bad sparkplugs, corroded connectors), fuel related (dirty injectors, dirty throttle body) and air related (vacuum leaks) to name a few.

[KenONeill]

@Fio - The oily MAP sensor suggests to me that you should clean the crankcase ventilation system because that's pretty much where the oil must have come from.

 

As to the HT leads, are they stiff to the touch? Does the misfire improve if you clean them with a cloth and spray them with WD40? If so, then in UK conditions a new set of HT leads will certainly improve and may cure the misfire, and probably give enough better mpg to justify the cost.

[Fio]

@KenONeill ill give the crankcase breather a clean too thanks, I've managed to locate two Allen bolts, is that all that holds it in place?

 

With the ht leads, they aren't especially stiff, but the metal parts that clip on the spark plugs are quite crusty, they are pretty inexpensive so will try that on pay day. I've allready changed the dizzy cap and rotor arm, plugs are quite new too., all this made some improvement.

I've posted this video where you can see the engine shaking a bit, might sound stupid but I'm not sure if its normal or if its a misfire (my last car misfired so severely at idle it looked like it would jump out of the car!)

 

p.s sorry for hijacking this thread!

[RicardoM]

8 hours ago, Fio said:

I've posted this video where you can see the engine shaking a bit, might sound stupid but I'm not sure if its normal or if its a misfire

It is a slight misfire. As I've said, it's difficult to diagnose using only the sight and the hearing. The video below is very informative.

Might help checking also for worn engine mounts.

[Santa2512]

In terms  of  a misfire,

 

i'd say thats fine, i cant discerne   anything untowrd

 

With regard to engine vibration,  again  it looks ok, if anything better than mine lol

 

As Ricardo says, and he beat me to it,  look at the  engine / geatbox mounts,  

 

There prolly either on the hard end of the scale by now, or worn out and offering little / no damping

 

There is i'd say 3-4mm  of clearance between the gearbox damping bush and the block on the gearbox,

 

Our Lower mount looks to have quite a bit of movement. too,, but that may be normal, as i have no other vehicle to use as a reference.

 

I did find an online site that soley concentrayed on replacement bushes ,  i think the gearbox housing was about £8   not sure on the lower.

 

If your feeling flush, see if anyone does polybushes     big money but top notch

 

 

[Fio]

Thanks guys, the engine mounts do look original and old to be fair. Nice video too.

You've all been a great help, awesome forum!

Cheers!

[Santa2512]

OK, time for a full update .

 

Car arrived back yesterday, and the new old stock thermostat housing the day before.

3 litres of fresh G13 and  a dry day

 

First of, drain the old coolant - a ball check showed 1 ball, so not really much antifreeze/ coolant in there. It also looked more brown than pink.

Popped off the rad temp sensor, and the lower rad hose and drained the old coolant into a container.

Looking aat the expansion bottle, the level was still high, so i opened the cap, and not much happened.

Dropping the lower hose of the expansion bottle showed a small trickle of coolant,   - not good, but corroborated why i had a lot of coolant in the bottle last time.

This made the coolant escape the bottle when trying to bleed it last time.

 

Once drained, it was evident there was a lot of debris in the expansion bottle. so i whipped it off, and went to work with a hose.

The cause of the poor lower exit flow  then became visible.   2 large plugs (small pinky nail size) of concentrated sediment were jammed in the aparture. 

I removed them and made sure the tank was clear and drained properly.

 

Backflushed Rad, block,  & heater matrix. Removed old thermostat housing and fitted the new old stock.

Now what was interesting is that the VAG group have changed the coolant temp sensor from the T shape to the current round type.

So there is now NO visible difference between the VAG part & a pattern part.

 

The pattern part has the part number on it, the OEM part just has VW Audi Skoda logo's on it.

Refitted all hoses, and double checked all done up  - wouldnt be the first time   

Reconnected all electrical plugs removed  and removed the coolant temp sensor.

 

Refill time:-

 

Following the process outlined on the board 

1.5litres of G13 followed by 1.5 litres of H2o

1litres of G13  wich filled to the top of the cooant temp sensor.

Temp sensor replaced. & follwed by a further .5 litre of G13 in the expansion bottle

 

I left that lot to settle while i cleaned the map sensor and prepped for bleeding.

Looking at the expansion bottle, the level was sitting firmly on MAX

 

Bleeding.

Started the engine and sat and waited,

This time the idle dropped from 1100+ before the engine temp gauge got off the peg,  (last time it didnt drop until it got to 70c)

After a long long long time the needle started to move and coolant started to circulate into the expansion tank.

Looking at the level now, it was above the MAX mark, almost at the radius of the top! (i'm thinking i may have to syphon some out when cold)

The temperature rose and got to 90c (approx) needle slap bang in the centre of the gauge.

And sat there !   for a good 20 minutes it just sat there, with circulated coolant & air comming out into the expansion tank.

 

A couple of times i thought it was going to overflow, but it thenit dropped back to a steady  stream of circulating coolant from the stat into the expansion bottle. 

100 degrees came and still the same. No fan intervention, and coolant and air still comming out of the stat.

Then the fan kicked in   i was going to pop the cap on then but for reasons unknown, decided to wait.

However i noticed that the level of the coolant in the expansion bottle had dropped  a lot!! 

The fan stopped and i replaced the cap. the coolant level was on MIN,  i left the engine running and checked the dashboard temp.

Just over 90 and still falling! 

Let it idle for a few minutes and turned off,

 

Ive checked about 20 mins ago, and its on MIN still. 

Burped top and bottom hoses, and it stays on MIN

When it's fully cold i will top up the expansion bottle to just over the midpoint  MIN-MAX

and recheck the antifreeze level.  I'm reckoning 3 balls

 

So by my reckoning I'm just about on 50:50 

 

I'll get it out for a long run tommorow and see how it does  

 

Mart

 

 

 

 

 

 

Edited 30 July, 2017 by Santa2512

[Santa2512]

Just been out and checked cold.

 

40cl added to bring it to 3/4 mark on the expansion bottle

 

Ran it up again.  Stat opens at around 90c, you see the gauge in car drop!  then it returns to around 90c    i had it ticking over for over 30 mins,

 

Once the stat opens you see coolant flowing into the expansion tank.

 

I dipped it when i first went out and the concentrations levels were good (3 balls), but with the added 40 cl in the expansion tank it was reading (2 balls)

 

i'll check it again tommorow as its had 30 mins to circulate now.

 

Indicator & rear wash wipe tommorow

 

 

Mart    

 

[Santa2512]

Indicator and rear wash wipe done today

 

I used the car to see how the new stat & housing is doing ..

 

Interesting until the car gets to 70c, it chugs below 2000 rpm, still drivable, but chugs

 

Once it hits 70c its fine ... 

 

I checked the MAP yesterday, it had a small film of oil on it, but nothing untoward.

 

Anyone know if you can test it in situ? and how to do it?

 

Edit = just tried unplugging it once the car was running --  it died immidiatly  - plugged it back in and it ran 

so it is working -- 

 

I'll get him to run some redex through the tank

 

 

 

Coolant was fine came up to  90C rising to 100c, then the stat opened and it dropped back to just under 90c

 

Air still being expelled, but thats to be expected,  level in the expansion bottle was stable, with a good concentration of antifreeze 

 

Ill get him to run it home tonight and feedback to me

 

Mart

Edited 31 July, 2017 by Santa2512

[Santa2512]

Feedback from the run home  -26miles  Mway & A roads

 

gauge hardly moved from 90c 

 

   thats a big improvement

 

Just the low temp chugging to look at next

 

 

[Pod56]

Re bleeding the coolant. I've had reasonable results by filling up the coolant reservoir and bleeding it from a heater hose on the bulkhead. I make sure I have a column of water by burping the main rad hoses. When I run the car, it rarely needs any topping up. Check the heater is working and Bob's your parent's brother.

I would like to say, Ricardo nursed me through a difficult top end rebuild 18 months ago. Now although we got off to a strained start with our communications, he was A1 and very patient with me.