Coolant leak detection

[Razor61]

Not strictly Lexus LS400 related but still relevant and may help someone else.

I had a large coolant loss on my other car, Audi A4 2.5tdi which the mrs drives, coolant was splattered between the timing belt covers and the radiator. I had to top up 2- 3 litres the first time the ‘low coolant’ error came up so a pretty dramatic loss. So I got the car on the drive, removed the timing belt covers to check if it was the water pump, it was all dry as far as I could see and no dripping from underneath that area. The symptoms didn’t fit with a leaking water pump anyway but had to check. So started it up and let it get up to temp to see if I could see any leaks anywhere. I couldn’t see anything at all, the mrs did a few miles round trip, checked the coolant the next morning, coolant splattered again in the same area but not swimming in coolant and had to put in another couple of litres. I’ve not had to go in depth checking for coolant leaks before so did some research (the web) and decided to purchase a ‘US PRO Tools 19 Piece Coolant System Pressure Tester Kit,  5226’ from eBay for £74. Yesterday I removed the undertray and bumper so I could see all round the readiator etc. So I attached the tester, pumped some pressure into the coolant system and found the leak in a few seconds, picture below which is self explanatory. I was initially stood directly in front of the radiator so got soaked a bit before I realised I was stood in front of the leak!

Just running the car to temp wasn’t a good test for this particular type of leak, it needed to be under pressure so in effect driving the car. Of course when driving the car the coolant was spurting out and hitting the front of the bonnet then mostly disappearing because of the air rushing by leaving just traces/evidence of coolant.

As you can see from the picture below, I didn’t need to be Sherlock Holmes to figure out where the leak is🤪 it’s the radiator. So new radiator needed and I’ll also replace the condenser because the aircon has never worked since I got the car 3 years ago. If the radiator has a hole in it then the condenser may have one as well and maybe that’s why rage aircon doesn’t work.

[runsgrateasanut]

In the old days, you might have put in Holts Radweld.  

I'd avoid Valeo as a brand.  They were responsible for a few issues back in the day.... 

[Jaystar77]

I would avoid using radweld like the plague (a phrase this pandemic has shown to be poor at best 😄).

Under the wrong circumstances it can cause all sorts of trouble in a cooling system.

[Razor61]

I did buy some k-seal but didn’t use it, thought better of it in the end. I’ve been looking at different makes of radiator, I’ll get a NRF or Nissens I think. The car isn’t worth spending a fortune on as it’s just a run about for the mrs, if it was the Lexus I’d get OEM or as near as possible. Getting the correct radiator is the hard bit, pretty sure I’ve found the correct one though after a lot of looking and comparing to the existing one. First radiator I’ve ever done on a car and not the easiest job on this A4. I had to cut through the plastic couplings on the radiator as I couldn’t separate the plastic joints on the top and bottom hoses. Sorted now though and ready for the new rad.

[runsgrateasanut]

Nissens a good reputation. I've had a Nissens replacement for my Lexus sat in a Box for three years now.  Unsure if after 27 years (should the Car come back from France) it would be wise to put it in.  I've seen the result of the Auto box to rad connecting pipe falling away with rust. Was it on a Valeo, perhaps? 

[Razor61]

On 8/23/2020 at 1:45 PM, runsgrateasanut said:

I've seen the result of the Auto box to rad connecting pipe falling away with rust. Was it on a Valeo, perhaps?

I think this was just for the LS430, the LS400 has the engine oil cooler combined in the radiator but the transmission cooler is separate from what I can see. I may be wrong though, if I am wrong someone will probably correct me😉

[runsgrateasanut]

6 hours ago, Razor61 said:

I think this was just for the LS430, the LS400 has the engine oil cooler combined in the radiator but the transmission cooler is separate from what I can see. I may be wrong though, if I am wrong someone will probably correct me😉

No, the Trannie fluid goes in and out of the Radiator via the bottom seperate pipe connectors.  I had the flexi pipes changed a couple of years back. The Rad seemed OK but you can't tell. Rust can happen on the inside which is more of a disaster than outside. The pipe connector fell off (rusted through) my Merc W140 just as I was about to enter my drive, one day. Total loss of gearbox use. Fortunately water didn't enter the gearbox so replaced Rad etc and all was fine. It was a '96 Car and Valeo longevity problems stem from about that time to early 2000's, I believe. If you see something different on your Car, someone may have put in an independent cooler for towing or safety purposes. 

[Razor61]

I stand corrected, I was just going off the exploded parts diagram which shows a separate transmission fluid cooler. Maybe this is was an option or I’ve got it all totally wrong😀 I’ll need to check mine for any signs of rust as soon as I can.