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Old 16th November 2021, 09:59   #11
FLYING BANANA
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Originally Posted by dave lincs View Post
Hi Bob hope you are well, if you had steam from the old cap and have changed the cap and now dont have any steam or coolant loss sounds like it is sorted

Also if you the 82oC thermostat those are about the running temperatures I would expect

Dave
Trikey suggested that I order a new PRT, which I have done. I’ll get that fitted if only for peace of mind. I check the water, and oil, every time I take any of the cars out.
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Old 16th November 2021, 13:32   #12
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I got a new cap from DMGRS a few months ago and almost immediately it started leaking from the overflow and there was steam coming out, i advised DMGRS of this and they sent me out another replacement cap.
I ran with the old cap on until the new replacement cap came and there was no more steam or coolant escaping so looks like there may be a small quantity of faulty caps.
I had only decided to change the cap as preventative maintenance type thing and DMGRS were very quick at sorting me out
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Old 16th November 2021, 14:49   #13
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There was a time when some folks simply replaced the o-ring on the cap and good as new. Did anyone ever record the o-ring size for the replacement?
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Old 16th November 2021, 18:39   #14
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DMGRS have got them: https://www.dmgrs.co.uk/products/rov...5d1d32b1&_ss=r

Keep well
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Old 16th November 2021, 23:37   #15
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Quote:
Originally Posted by SD1too View Post
Hi Bob,

I'm sorry to have to say this but I don't agree with what Michael (mbonwick) has said here. Your coolant temperature should never drop as low as 79˚. The thermostat is designed to keep it at a minimum of about 92˚. When the car is stationary or slow moving in traffic, this should steadily increase to 104˚ when the slow speed fan should trigger.

Your temperature is varying widely depending upon engine load which is not correct. Your system is not pressurising which means that you won't have the protection of a raised boiling point. When the conditions are right you will continue to lose coolant, but it will be intermittent. Having a 1.8 you're then at risk of the incorrect diagnosis of head gasket failure.

The thermostat is not "designed" to keep the coolant at 92˚C at all. It is designed to open at a specified temperature range to assist keeping the coolant temperature at an acceptable level. The overall system - of which the thermostat is only 1 part - is designed to keep the coolant at a relatively steady low-mid 90s˚C temperature. A good rule of thumb for the 1.8 is coolant temp 5˚C above the rating of the stat (i.e. for the OEM 88C stat, expect temps of 92/93˚C).
The aftermarket stats supplied by DMGRS are rated at 82˚C (so expect temps of 87/88˚C).
The other unfortunate side effect of the DMGRS stat is that it opens/closes over a much larger temperature range than the OEM design, so you get much wider temperature swings when coasting, as coolant (already at a lower temperature as the stat opened earlier) is still circulated round the radiator, removing heat faster than it is generated by the "idling" engine.

As for how I know this? I have both OEM and DMGRS stats and have done a far few comparative trials - both on and off the car. Incidentally, I've always regretted (solely from a research perspective) binning the original PRT from the car which gave a running temp of 96˚C.

Of course, there is a big IF in my original statement that this is only true if the fitted stat is a DMGRS example - if its not, and is a genuine MGR 88C part, it has obvious started opening early and should be replaced.


Finally, I'm not sure how you can make any conclusion on the correct (or not) pressurising of the system just on the fact that its not spewing steam out everywhere? Bob absolutely should be vigilant in case there is another problem, but at the end of the day it's a 1.8 with a very simple cooling system. Most problems are incredibly simple in nature and don't need a full scientific investigation, and not every K-series cooling issue leads to HGF...
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Old 17th November 2021, 08:13   #16
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Quote:
Originally Posted by mbonwick View Post
The thermostat is not "designed" to keep the coolant at 92˚C at all.
Hello Michael and thank you for your detailed reply. I find that sometimes it's helpful to use straightforward language in a technical explanation to show the principle and aid understanding but without going into great detail. That was my aim in this case.
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Originally Posted by mbonwick View Post
Finally, I'm not sure how you can make any conclusion on the correct (or not) pressurising of the system just on the fact that its not spewing steam out everywhere?
I didn't Michael. Please see the full evidence given by Bob in post number 1, of which steam is only one aspect.

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Last edited by SD1too; 17th November 2021 at 08:37..
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Old 17th November 2021, 19:55   #17
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Quote:
Originally Posted by FLYING BANANA View Post
Yesterday we had lots of steam coming out of the overflow pipe..
Where is your overflow pipe Robert? - cos I don't have one on my 1.8T.
Anyway, if you mean hot coolant was splattering around the top fo the header tank around the filler neck, than that's what it does. It's designed to simply splatter out from under the top of the cap.

TC
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Old 17th November 2021, 21:19   #18
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Quote:
Originally Posted by T-Cut View Post
Where is your overflow pipe Robert? - cos I don't have one on my 1.8T.
Anyway, if you mean hot coolant was splattering around the top fo the header tank around the filler neck, than that's what it does. It's designed to simply splatter out from under the top of the cap.

TC
Short pipe that comes out of the filler cap neck. Comes out to the left of the cap and points down towards one of the water pipes. The steam was coming out of this pipe. I put the old radiator cap back on it has stopped the steaming.

We are still getting some coolant loss, checked this morning and it had definitely gone down as the lower level indicator was dry.

Acting on advice from another forum member I’m going to book Banana in to have a pressure test.
The new PRT has turned up so that might have to be fitted.
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232750. Be patient Banana, we will soon be back together and enjoying the shows again.

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Old 17th November 2021, 21:52   #19
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Quote:
Originally Posted by FLYING BANANA View Post
Short pipe that comes out of the filler cap neck. Comes out to the left of the cap and points down towards one of the water pipes. The steam was coming out of this pipe. I put the old radiator cap back on it has stopped the steaming.

We are still getting some coolant loss, checked this morning and it had definitely gone down as the lower level indicator was dry.

Acting on advice from another forum member I’m going to book Banana in to have a pressure test.
The new PRT has turned up so that might have to be fitted.

Possibly that with your first coolant loss you entrained some Air in the system
and that has lowered your coolant level as the air as worked back to the header tank
But fitting the recommended PRT , A proper bleed of the coolant system and a pressure test should find / iron out any problems . Did you order a new cap as well ?
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Old 17th November 2021, 22:03   #20
FLYING BANANA
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Quote:
Originally Posted by TourerSteve View Post
Possibly that with your first coolant loss you entrained some Air in the system
and that has lowered your coolant level as the air as worked back to the header tank
But fitting the recommended PRT , A proper bleed of the coolant system and a pressure test should find / iron out any problems . Did you order a new cap as well ?
Yes to another cap on order.
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232750. Be patient Banana, we will soon be back together and enjoying the shows again.

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