Temp gauge testing

[BennSport]

So even with me not retightening my timing belt after the initial installation, it’s unlikely that the problem is due to the water pump pulley?

[Tom]

So even with me not retightening my timing belt after the initial installation, it’s unlikely that the problem is due to the water pump pulley?

Right, that's less likely than the more common causes -- thermostat sticking/bad (or cheap VW unit); head gasket; internally or externally blocked radiator; inop fans/thermoswitch/relay; bad water pump (some cheap rebuilds had slipping pulleys brand new); undetected leak (pressure test!); bad cap; excessive antifreeze mixture; probably a few other things I'm forgetting...

If it were me, I'd start by pressure testing the system for leaks. They can be sneaky but the pressure tester will reveal all. Then confirm the fans are working as intended. Then use a point and shoot thermometer to see if the coolant is circulating through the radiator and, if so, if it is cooling as expected.

I'd re-tension the belt either way. If you worry it is loose enough for the belt to slip, I'd be more worried about it jumping teeth and bending a valve. How was it tensioned when it was installed? If you used the factory tool set to new-belt spec, it's probably too tight, but kind of a gamble to run it without checking.

[944m3]

I had similar issue. I switched to a Wizard aluminum radiator with integrated oil cooler. Now temp is consistent, usually just above the first line. Even in 90+ summer days. I have my standalone displaying the coolant temp and it’s usually 194ish. On cold days maybe around 185ish.

I think 30+ year old radiators are probably to crusty. Plus you never know what previous owners used for coolant.

https://wizardcooling.com/i-30501843-19 ... =944+turbo

[BennSport]

Today I pressurized the system to 15 psi and it dropped to 13 after 10 minutes. After spraying with some soapy water, I wasn’t able to find any leaks but I also only spent a couple minutes looking. Following that up with a rental compression tester, none of my readings would hold after I stopped cranking. I assume that’s the rental tools fault, as I don’t think my car would be drivable if I wasn’t able to hold any compression in the cylinders.

[Tom]

Today I pressurized the system to 15 psi and it dropped to 13 after 10 minutes. After spraying with some soapy water, I wasn’t able to find any leaks but I also only spent a couple minutes looking. Following that up with a rental compression tester, none of my readings would hold after I stopped cranking. I assume that’s the rental tools fault, as I don’t think my car would be drivable if I wasn’t able to hold any compression in the cylinders.

A drop in pressure is sometimes just a bad seal where the tool sits in the reservoir. Did it seem like you got a good seal? I'd let it sit longer and check if you can see anything dripping.

Not sure what's going on with the compression test/tester, but I agree the car wouldn't run if the cylinders had no compression.

[944er]

Over the years I've found that an initial drop in cooling system pressure with a pressure tester can be attributed to the hoses relaxing over a few minutes. Make sure the pressure keeps dropping before confirming it as a leak.

[BennSport]

The tester did seem to be sealing well to the overflow tank, but I wonder if any of the other fittings/attachments to the tester weren’t sealing properly. I’ll throw the tester back on and leave it for a while to perform a leakdown, but during my initial test I saw nothing dripping or leaking. Regarding the compression tester though, I am stumped.

[BennSport]

Well I put the coolant tester on for about 20 minutes or so, and dropped about 2-3 psi. Not a single drip or any sign of a leak, which has me a bit worried. Could it be a head gasket or faulty oil cooler? I replaced my faulty oil cooler seals a couple weeks ago but made the mistake of not testing the cooler element.

[Tom]

Well I put the coolant tester on for about 20 minutes or so, and dropped about 2-3 psi. Not a single drip or any sign of a leak, which has me a bit worried. Could it be a head gasket or faulty oil cooler? I replaced my faulty oil cooler seals a couple weeks ago but made the mistake of not testing the cooler element.

What kind of tester is it? Sometimes (often) when the pressure drops without any leaks like that it's simply because the tool isn't sealing completely at the mouth of the coolant tank and/or because the overflow tube isn't clamped tight enough.

Any signs of coolant getting into the cylinders -- steam cleaned spark plug? Coolant visible in cylinder after pressure testing? Lumping hard starts with steamy exhaust? If it were a HG if cooler seal, it would get worse over time and you'd the symptoms would become more obvious, is it getting worse>. The longer you've driven it without that, the more likely it's just a true cooling system issue like an old barely-working radiator.

[BennSport]

I’m using an autozone rental coolant pressure tester, so it could be faulty. My spark plugs definitely aren’t steam cleaned, but I do get hazy exhaust on cold start. I’m wondering if that’s just to do with the cold or if there’s something else affecting that. I also struggle a lot bleeding all the air out of my coolant system. It seems like I can never get it fully bled, which makes me wonder if it is in fact a HG. If it is my radiator, do you think removing it and taking it to a radiator shop for a power flush would suffice in restoring it? It’s hard to find the plastic radiators for a reasonable price and I don’t trust aftermarket options.