Engine runs cold

[RAMurphy]

Welcome to, this post just proved it, this great forum.

 

[mattbta]

.45 Colt is trimmed and fit. I’m currently flushing the heater cores because there’s a slice of the old radiator…View attachment 411651

For the experts here, is that due to mixing Dexcool and traditional? Or just junk from age?

 

[Breadman03]

Holy crap....what a mess.

Yeah. The .45 is working well and the front heater core is working great, but the rear is useless. We have to order some house and fittings so that we can open it up and flush it directly instead of trying to flush it from the front because the rear connectors are being stubborn and I’m certain we’re going to have some breakage getting it apart.

 

[hmclaughlin67]

You'll want to thoroughly check the fan relays to make sure they're operating correctly. If I'm not mistaken, the fans should (may?) come on automatically if the A/C is turned on. Also, pull the two connectors to the PCM and look for water migration and pin fitment.

Having said that, the slow warmup is an issue. The stock radiator has a restrictor in the fitting for the small hose that runs from the right (passenger) side of the radiator to the surge tank. If the radiator's been replaced at some point and it no longer has that restrictor, the engine might never warm up, or could take a long time. Too much flow into the surge tank causes that problem. You can test the theory by pinching off -- mostly but not completely -- the hose to the surge tank to see if you get a quicker warmup.

There are several threads on here about the restrictor, and I'll post a short one below. If you're interested in others, search or yell and we'll see about finding a couple more.

07 Tahoe engine hot ac turned off

You are on to something there, with the radiators. Struggled with the hot, AC off bs for a while. I made a number of cooling system improvements at the same time, so it took a while to figure it out. But I think I have it solved on my machine. Source of the problem: Aftermarket radiator...

www.tahoeyukonforum.com

The restrictor ended up being the issue. Few days of driving now and temp has been good. My dad discovered that a .45 Colt's primer hole is just about the same size as the factory restrictor. Just wanted to post this just in case anyone else in the future has the same problem

 

[tooleyondeck]

I love reading these cradle to grave threads...

 

[Breadman03]

I love reading these cradle to grave threads...

I always wanted to restore a car, but thought I’d start with something like a classic Beetle and have a garage bay to do it in, not something with miles of wiring and on the curb

 

[tooleyondeck]

I always wanted to restore a car, but thought I’d start with something like a classic Beetle and have a garage bay to do it in, not something with miles of wiring and on the curb

honestly these GMT800s are one of the easiest to work on yet least appreciated project cars. In 5 years my 03 Yukon will qualify for an antique license plate and I don’t see any reason why it won’t still be running strong by then!