overheating - Solved - Thanks! :)

[Henny 0]

Hi all!

 

Right then, my nice new engine will sit and idle nicely for hours on end with the oil temp going nicely upto around 100 and the water temp going to around the same.

 

However, when I drive it, the oil temp drops (as it should having a Mocal on there! ;) ) but the water temp seems to go up a bit more, then drop for a while.... BUT as soon as there is any load put onto the car (I live in quite a hilly place) the temps shoot up and she starts to overheat...

 

Now, she's had ALL new waterpipes, new uprated (blue) expansion cap, a new thermostat, a new water pump, a new uprated slimline fan (which IS switching on at the lower temp from the fan switch) and the old radiator which is getting hot evenly top and bottom... I've junked the original oil cooler, so the oil is now only cooled by the Mocal, and there's a pair of proper VW water hoses in the plumbing to do the bypass of the cooler... 8)

 

She's running 2L of G12+ and 2L of water and she's boiling that lot in the pipes making excess pressure.... There's no leaks or airlocks, she's just getting very hot when under load...

 

The engine starts first time, and is running sweetly, although it's obviously not fuelling correctly... The timing is set to 6deg BTDC at 2250 as per normal spec and I've set the COpot to 850ohm to richen her up to make up for the extra 159CCs and engine mod's she's running with... most sensors are new (blue/black water temp, oil temp, both oil pressures and knock)

 

Anyone got any ideas what could be causing this overheating under load?

 

Any ideas welcome, no matter how simple/over the top they may be... This engine has had a LOT of work done, but this has got me stumped, so I'm open to any suggestions... 8)

 

Thanks...

[h100vw 0]

Is it reallly overheating? Does it spit water out or is it just the inication that is the problem??

 

VW says in the handbooks that anywhere on the gauge with the LED off is normal.

 

Gavin

[Henny 0]

It's popped one expansion tank (probably a faulty tank though to be honest) and it's over pressuring the pipes.... something's not right...

[kvwloon 0]

Hmmm, don't shoot me down in flames coz i'm guessing you guys are far more up on this than me to start with,buuuuuut, ....to my logic, surely if you know the water system is all good, it can ONLY be a lack of adequate cooling from the Mocal, either because the Mocal isn't getting enough cooling airflow, or the design of the Mocal can't handle the extra heat transfer on it's own. I thought the Mocal was more intended as an additional supplement to the original oil cooler, rather than a replacement? Is it feasible to temporarily de-bypass the original oil cooler, and run the Mocal as an addition to see if things improve? I know I'm going to get shot down in flames now, I'm no engine expert, just thinking out loud....... :wink:

[Henny 0]

I'm not gonna shoot anyone down in flames, I need some help on this and I'm open to any suggestions... 8)

 

The Mocal just cools the oil and is doing it's job well... the oil hasn't yet been above 110 degrees and tends to sit around 95 when driving which is a good 10 degrees lower than it was on the old water cooled system... The original heat exchanger has been completely removed as there isn't enough room on a G60 to run both mocal and original coolers at the same time...

 

Your post has made me think about which way the water is flowing around the sytem though, and I'll have a look into my box of pipes tomorrow to work out how it used to flow, and how it now flows to see if there's a major difference now I've got rid of that cooler... 8)

 

Thanks... 8)

[kvwloon 0]

Ah of course, suppose the Mocal just runs the oil through it's air-cooled matrix, without water being involved....knew I was missing the point somewhere! Anyway, hope I have kind of helped, somehow, and that you solve it!

[King_prawn 0]

The G60 doesnt have a oil cooler as standard, it had a water-oil heat exchanger. If he's removed this then it should run a lot cooler if anything, I know mine does.

Water temps rise quickly to about 90-100 when stationary but once moving it plummets to just over 70.

I thought lower resistance on the co pot richened the mixture?

As for a remedy I dont really know, seems like you've already replaced everything.

[paulg60 0]

i'd have a look at the expansion tank cap they have a pressure relief valve in them and if you say the system is building to much pressure i'd go for that. i had it once on mine the O-ring on the cap lifted out slightly as i screwed it in causing the pressure relife valve to stick :) hope this helps

[King_prawn 0]

Thats weird, seems i only got part of this thread when i first clicked on it, my post seems kinda useless now. And how come it says posted at 9:13, its 22:20, strange

[Henny 0]

Thats weird, seems i only got part of this thread when i first clicked on it, my post seems kinda useless now.

 

Dunno... it cleared it up a bit better than I did though! ;)

 

And how come it says posted at 9:13, its 22:20, strange

 

You've not got your time zone set to GMT +1 in your profile... ;)

[andycowuk 0]

I have a couple of ideas that spring to mind....and I am sure there is another one coming.......

 

I, likeKing_prawn, am not sure that which way for richer on the co pot.... I would try putting it to the rich extreme for a test to make sure your not running lean, which gives a much hotter explosion.

My second thought is less plausible, because of the work you've had done, but do you know that you have good compression?? When the h/g went on my last car, the water pipes pressurised (really hard) once I had been a drive, but were ok at idle......are there any other signs that this may be the case?

 

When does the pressure ease.....can you drive, get hot, then idle and it cools? or do you have to turn off so it can cool?

 

One final thought, is that the glycol in the antifreeze is for exactly that purpose....antifreeze, water on its own has better cooling properties, could i recomend you trying to increase the water in the mixture, and perhaps try some of that water wetter stuff......I dont have it but afew peeps have said its funky sh*it!

 

HTH (even a little!)

[Henny 0]

the expansion tank cap is OK and the seal is good, I've tried 2 caps on it now just in case ;) it was the tank that was cr@p and that blew out the join in the side... It'll be going back to Euro tomorrow with an unhappy me to get a refund and an apollogy! ;)

 

There's definately good compression there, and it's not the head gasket leaking that's pressureising the system 'cos there's no smell in the expansion tank and it's not getting THAT pressureised, the pipes are firm, but not rock hard...

 

I can drive the car normally on flat roads and down hill, it's only when I start to have to climb/load up the engine that the temp rockets up... she cools down pretty quickly once you turn of the engine, and the fan over-run works well too... if left on idle once hot, she stays hot, maybe drops a few degrees, but not a lot...

 

I was wondering about the CO pot too... I'm of the opinion that the car isn't fuelling properly possibly due to the map and so is running lean which is causing it to overheat... :?

 

I'm gonna rig up my A/F gauge tomorrow and see what that says about the situation... ;)

 

Thanks for the ideas so far... they've all been useful and have put ideas into my head for things to check... 8)

 

Keep 'em coming... 8)

[Henny 0]

EEEEEK!!! I've just made my first visit to VWVortex and found out that the bigger the resistance the LEANER the fuelling! :shock:

 

I'm gonna go adjust it NOW... :? :roll: :|

 

:oops:

[W3RKD 0]

EEEEEK!!! I've just made my first visit to VWVortex and found out that the bigger the resistance the LEANER the fuelling! :shock:

 

I'm gonna go adjust it NOW... :? :roll: :|

 

:oops:

 

henny set your pot to 550. this is a safe value untill you sort ya custom one out... whats ya pot at now ?

[Henny 0]

550 now... Phew... Thanks Daz... :mrgreen:

 

Was originally 419 then I set it to 750 (not 850 as I put in the first post :oops: )

[Henny 0]

just a quick bit of additional info, the MOT emissions were 0.44% CO (limit is 3.5%) and 13ppm HC (limit is

 

This just struck me as very low, but I've never really messed around with tuning, only with building cars, so I'm new to this side of things... :oops:

[h100vw 0]

Don't forget you have very few miles on this BRAND NEW engine Henny. Heat production is going to be high due to tight tolerences etc.

 

I doubt if you could have plumbed it wrong using VAG hoses for your bypass, they wouldn't fit. My Golf used to heat up quick in traffic like King Prawns and then drop once moving again.

 

 

 

Another thought, if you have had all the water out of the system, can you get hot air from the heater? Airlocks.

 

Your MOT figures are not unusual IMHO, nice flowing efficient head ECU with Lamdba control etc. No unburnt fuel leaving the cylinders.

 

Gavin

[Henny 0]

Cheers Gav,

 

I think that I need to try and put a few more miles on her yet (there's only 80 odd so far)... I may just be being over cautious as I don't want to kill her before I get to enjoy her! ;)

[h100vw 0]

Seriously, I don't think you need to 'sweat it'. Pun intended.

 

I would be worried if the temp shot up and never came down. But as it goes up and down, I'd say it was ok. The gauges read from around 70 to 100ish degrees so the scale isn't too clever really. A big swing in the needle isn't all that much, as a percentage. As my old physics teacher said 'it's all about percentages'.

 

You can't really go on what was indicated before the rebuild as so much has changed. What does the oil read on the open road? My Golf showed about 70-80 most days at motorway speeds. You got heat soak for a short while as you slowed down. But again half a mile of clear road would see it drop.

 

Personally, I thing running it up those hills under load will be really good for it. As per that Yank website. Certainly loads better than dribbling to work at 50.

 

Gavin

[Bobby 0]

my c has started to do the same since it had a top end rebuild i think it may be down to a blockage in the water ways, anyway hope u get it sorted mate. :mrgreen:

[Henny 0]

Gav? I'll get ya a pint in next time we meet up! ;)

 

I've just been for a 50 mile run, the temps went right up near 110 on the water with oil temps just nudging 100 after about 15 miles, and then, all of a sudden the engine seemed to free up lots and the temp dropped down near 100 water and 93 oil, which is pretty much where it stayed for the rest of the run apart from when I got stuck in traffic and the water nudged upto 110 again...

 

She seems to be running a whole lot better (although she still needs setting up properly, but after she's bedded in! ;) ) and is lots less hesitant below 2K

 

I did find that there were a couple of dodgy jubilee clips(not actually made by Jubilee, but some other naff make) which wouldn't tighten fully the other night, so I think that this was introducing a vacuum leak which wasn't helping matters, but all in, I reckon that you were spot on with the tollerances thing and I was just being mega paranoid... :oops:

 

with any luck, things can only get better from here on.... :D 8)

 

Daz? Thanks a lot to you too, There's a pint waiting for you at inters too if you want it... ;)

 

And to all others who added thoughts, THANKS! 8)

[h100vw 0]

SWEET!! :D

[W3RKD 0]

no probs mate pleased to help...have also mailed you about parcel too...

[Henny 0]

Well, just to end this thread on a happy note...

 

I've now done almost 2000 miles in my C, and the overheating hadn't been an issue anymore... until the rad burst... :roll:

 

I've now fitted a Rad from Euro (it's had the VAG logos sanded off it badly, so I can tell it's OEM!) and I've just been on a 100 mile run (I was bored! ;) )

 

Oil temp didn't go over 102, and water didn't go over 95! :crazyeyes: And that was caining the hell out of her on the motorways and tight and twisty A roads near where I live... 8)

 

In all honesty, I think that I had 4 faults here which you may want to make a note of if you have overheating problems...

 

1) first fill up I got an airlock in the system due to not twisting the top hose to allow the expansion tank pipe to be at the top/be the highest point...

2) the wiring to the fan was crap and was only supplying around 8V to the fan... :?

3) the engine timing was a way off, and it was a new engine and so ran hotter anyway....

4) the rad appears to be an aftermarket one, and isn't as well made as a genuine one....

 

added together, these 4 now being cured, I'm running cooler with my new engine than I ever did with my old G60 block... 8)

 

Thanks to all who helped solve this one (4!) 8) 8) 8)

[colinstubbs 0]

i had a garage fit the fan plug wrong way round, when she started to work hard the fan counteracted the airflow through the radiator at speed. give away is hot air out the grill when you stop. probably not your prob but a possibility?simple fix anyhow. good luck